Bharat Sanchar Nigam Limited

EWSDSYSTEMS ARCHITECTURE

NETAJI SUBHASH CHANDRA BOSE TELECOM TRAINING CENTREKALYANI, NADIA, WEST BENGAL, PIN – 741235

EWSD Architecture

EWSD Architecture

Basic Hardware

Page No.

1.1 System Overview 3

1.2 Digital Line Unit 28

1.3 Line Trunk Group 81

1.4 Switching Network 134

1.5 Coordinating Processor 167

1.6 Message Buffer 208

1.7 Central Clock Generator 233

1.8 System Panel 254

2

System Overview

What is inside?

1. Introduction

2. System Features

3. System Architecture

3.1 DLU

3.2 Line/Trunk Group

3.3 Switching Network

3.4 Coordination Area

3.5 Common Channel Signaling Control

4: Subsscriber/Administration facilities in EWSD

Annex. 1: System Data

Annex. 2: Abbreviations

Annex. 3: Present status of EWSD exchanges in DoT network

3

EWSD – System Description

1.0 Introduction

After years of being treated as a luxury, telecommunications has come into its own in the Eighth Plan. The Department of Telecommunications has announced ambitious plans for the addition of 7.5 million lines to the existing 5.8 million by the end of the 8th plan (1992-97) as compared to only 3.2 million in 1982-92.

To bridge the gap between the supply and demand DoT invited a tender for 200,000 lines of digital switching equipment on Rupee payment. In the industrial policy of July 1991, Telecom. equipment was delicensed and thrown open to foreign investments. Consequently six new technologies were planned to be validated. These foreign suppliers set up their validation exchanges, each of 10,000 lines capacity (including two RSUs of 2K each), at different places, e.g. EWSD of Siemens (Germany) at Calcutta, AXE-lO of Ericsson (Sweden) at Madras, Fetex-150 of Fujitsu (Japan) at Bombay, OCB-283 of Alcatel (France) at Delhi etc.

Three new Digital Switching Systems, i.e., EWSD), AXE-10, Fetex-150, which got validated first, were inducted in the Indian Telecom. Network & three Iakh lines were imported from these three suppliers. In addition 3.5 Iakh lines were also imported on lease basis from these suppliers. Subsequently four more switches, i.e., OCB-283 of Alcatel (France). 5ESS of AT&T (USA), System-X of GPT (UK) and NEAX-61E of NEC (Japan) also got validated.

EWSD is one of the two technologies selected for TAX and is also the technology for lntclligçnt Network and Mobile Communicition. This article gives a general introduction to the EWSD) system, its features. architecture and facilities.

2.0 System Features:

EWSD Digital switching system has been designed and manufactured by M/s Siemens, Germany. The name is the abbreviated form of German equivalent of Electronic Switching System Digital (Electronische Wheler Systeme Digitale). EWSD switch can support maximum 2,50,000 subscribers or 60,000 incoming, outgoing or both way trunks, when working as a pure tandem exchange. It can carry 25,200 Erlang traffic and can withstand 1.4 million BHCA. It can work as local cum transit exchange and has CCS No.7, ISDN and IN capabilities.

4

3.0 System Architecture:

The main hardware units of an EWSD switch are as under :(1) Digital line unit (DLU) - functional unit on which subscriber lines are terminated.

(2) Line/Trunk Group (LTG) - Digital Trunks and DLUs are connected to LTGs.

The access function determined by the network environment are handled by DLUs and LTGs.

Figure – 1 : Distributed controls in ESWD

5

(3) Switching Network (SN) - All the LTGs are connected to the SN which inter connects the line and trunks connected to the exchange in accordance with the call requirement of the subscribers. CCNC and CP are also connected to SN.

(4) Coordination Processor (CP) - It is used for system-wide coordination functions, such as, routing, zoning, etc. However each subsystem in EWSD carry-out practically all the tasks arising in their area independently.

(5) Common Channel Signaling Network Control (CCNC) Unit - This unit functions as the Message Transfer Part (MTP) of CCS-7. The User Part (UP) is incorporated in the respective LTGs.

Block diagram of EWSD is given in Figure 1. It also shows that the most important controls are distributed throughout the system. This distributed control reduces the coordination overheads and the necessity of communication between the processors. It results in high dynamic performance standard

For inter-processor communications, 64 kbps seripermanent connections are set through SN. This avoids the necessity for a separate interprocessor network.

3.1 Digital Line Unit (DLU)-

Analog or Digital (ISDN) subscribers or PBX lines are tenninated on DLU (Figure 4). DLUs can be used locally within the exchange or remotely as remote switch unit, in the vicinity of the groups of subscribers.

DLUs are connected to EWSD sub-systems via a uniform interface standardized by CCITT, i.e., Primary Digital Carrier (PDC) to facilitate Local or Remote installation. A subset of CCS# 7 is used for CCS on the PDCs.

One DLU is connected to two different LTGs for the reasons of security (Figure2). A local DLU is connected to two LTGs via two 4 Mbps (64 TSs) links, each towards a different LTG. In case of remote DLUs maximum 4 PDCs of 2 Mbps (32 TS5) are used per DLU, two towards each LTG. Hence total 124 channels are available between a DLU and the two LTGs, out of which 120 channels are used for user information (speech or data) and signaling information is carried in TS16 of PDCO and PDC2.

Within the DLU, the analog subscribers are terminated on SLMA (Subscriber Line Module Analog) cards (module). Similarly Digital (ISDN) subscribers are terminated on the SLMD modules. Each module can support 8 subscribers, hence has 8 SLCAs (Subscribers Line Circuit Analog) and one SLMCP (Subscribers Line Module Circuit Processor).

6

One DLU can carry a traffic of 100 Erlangs. A standard rack of DLU (local or remote) can accommodate one DLU of 944 subscribers or two DLUs of 432 subscribers each. Smaller racks (Shelter) are also available for remote DLUs in which lesser number of subscribers can be equipped.

Figure – 2 : Applications for and connection of Digital Line Unit

In case the link between a remote DLU and the main exchange is broken, the subscribers connected to the remote DLU can still dial each other but metering will not be possible in this case. For emergency service DLU-controller (DLUC) always contain up-to-date subscribers data. Stand Alone Service Controller card (SASC) is provided in each R-DLU for switching calls in such cases. This card is also used for interconnecting a number of remotely situated DLUs (maximum 6), in a cluster, called a Remote Control Unit (RCU), so that subscribers connected to these remote DLUs can also

7

talk to each other in case the link of more than one DLU to the main exchange is broken. An EMSP module (EMergency Service equipment for Push-button subscribers) is used to make internal calls by DTMF subscribers when the remote DLU link is broken.

All DLUs are provided with a Test Unit (TU) for performing tests and measurements on SLCAs, subscribers lines and telephones. An ALEX (ALarm EXternal) module is used for forwarding external alarms, i.e., fire, temperature, etc, to System Control Panel (SYP). Number of SLMAs are accordingly reduced to accommodate these modules. The main components of a DLU as shown in figure3 are

•SLMAs and / or SLMDs

•Two Digital Interface Units Digital (DIUD) for connections of the PDCs.

.Two DLU Controls (DLUC)

•Two 4 Mbps networks for the transmission of user information between SLMs and the DIUDs.

• Two control networks for the transmission of control information between SLMs and DLUCs.

• TU, EMSP, ALEX modules.

8

Figure – 3 : Main Components of a DLU

9

Figure – 4 : Line / Trunk Groups

3.2 Line / Trunk Group

The line/trunk groups (LTG) form the interface between the digital environment of an EWSD) exchange and the switching network (SN). The LTGs are connected in any of the following ways (Figure 4):

(i) Via 2/4 Mb/s PDCs with remote/local DLUs to which analogue or ISDN subscribers are connected

(ii) Via 2 Mbps digital access lines to other digital exchanges in the network, or

Via Signal Converter-Multiplexer (SC-MUX) to analog trunks from analog exchanges in the network. SC-MUX do not form the part of the EWSD exchange equipment

(iii) Via Primary rate Access lines to ISDN PBXs (ISDN subscribers with PA)

Functions

The primary functions of the LTG are as follows:

(i) Call processing functions, i.e., receiving and analyzing line and register signals, injecting audible tones, switching user channels from and to the switching network, etc.

(ii) Safeguarding functions, i.e., detecting errors in the LTG and on transmission paths within the LTG, analyzing the extent of errors and initiating countermeasures such as disabling channels or lines, etc.

(iii) Operation and maintenance functions, i.e., acquiring traffic data, carrying out quality-of-service measurements, etc.

The LTGs can work with all standard signaling systenis (e.g. CCITT No. 5, R2, No.7). Echo suppressers can be incorporated in the I TGS for the connection of long-haul circuits (e.g.. via satellite).

Although the subscriber lines and trunks employ different signaling system, the LTGs Present signaling-independent interface to the switching network. This facilitates the following :

10

Figure – 5 : Functional Units of the LTG

11

- flexible introduction of additional or modified signaling procedures,

- a signaling independent software system in the CP for all applications.

The bit rate on all highways linking the line/trunk groups and the switching network is 8192 kbps (8 Mbps). Each 8 Mbps highway contains 128 channels at 64 kbps each. Each LTG is connected to both planes of the duplicated switching network.

The functional units of the line/trunk group as shown in figure 5 are:

Line / Trunk Unit (LTU) is a logical unit that comprises 8 number of different , functional units, i.e.

- Digital interface unit ( DIU3O ) for connection of 2 Mbps digital trunks and either DLU or PA. One LTG can comprise four DIU30.- Code Receivers (CR) are Multi-frequency code receivers for trunks or DTMF subscribers.- Conference Unit, module B (COUB) for conference calls.- Automatic Test Equipment for Trunks (ATE:T) checks trunks and Tone Generators (TOG) during routine tests.

• Signaling Unit (SU) comprises Tone Generator (TOG) for audible tones, Code Receivers (CR) for MFC signaling and push-button dialing and Receiver Module for Continuity Check (RM:CTC), etc.

• Group Switch (GS) or Speech Multiplexer (SPMX) are used for DLUs or Trunks respectively. These are non-blocking time stage switch controlled by theGP.

• Link Interface Unit (LIU) connects LTG to SN via two parallel 8 Mbps SDCs.

• Group Processor (GP) controls the functional units of the LTG. The received signals from LTU, SU, GS/SPMX and LIU are processed with the help of GP software

In LTGG, GS and LI U have been combined into GSL module. Only LTGGs have been supplied to India. One LTG rack can accommodate 40 PCMs in five LTGG frames, each containing two LTGGs.

12

Figure – 6 : Switching Network

13

3.3 Switching Network

Different peripheral units of EWSD, i.e., LTGs, CCNC, MB are connected to the Switching Network (SN) via 8192 kbps highways called SDCs (Secondary Digital Carriers), which have 128 channels each. The SN consists of several duplicated Time Stage Groups (TSG) and Space Stage Groups (SSG) (Figure 6) housed in separate racks. Connection paths through the TSGs and SSGs are switched by the Switch Group Controls (SGC) provided in each TSG and SSG, in accordance with the switching information from the coordination piocessor (CP). The SGCs also independently generate the setting data and set the message channels for exchange of data between the distributed controls.

The switching network is always duplicated (planes 0 and 1). Each connection is switched simultaneously through both planes, so that a standby connection is always immediately available in the event of a failure.

Each TSG can accommodate 63 SDCs from LTGs and one SDC to MB. One SDC is extended from SGC of each TSG and SSG towards MB. Thus one TSG can handle upto 63 LTGs. The switching network can be expanded in small stages by adding plug-in modules and cables and if necessary by assigning extra racks. Optimized switching network configurations are available in a range of sizes. The smallest duplicated SN:63 LTG configuration which can handle 30,000 subscriber lines or 7,500 trunks when fully equipped is installed in a single rack and can handle 7,500 erlangs traffic. In its maximum configuration, the EWSD switching network has 8 TSGs and 4 SSGs (in 12 Racks) to connect 504 LTGs and has a traffic -handling capacity of 25,200 erlangs. SNs for 126 LTGs and 252 LI (LTGs are also available which can handle 6300 and 12600 erlangs traffic respectively.

The SN supplied in first 110K order contains only seven different types of module and each TSG and SSG is accommodated in a separate full rack. In the subsequent supplies SN(B) has been supplied which has only 5 types of modules and each TSG and SSG is accommodated in only two shelves of the respective racks. Remaining four shelves accommodate LTGs.

14

Figure – 7 : Structure of CP 113

15

3.4 Coordination Area

3.4. 1 Coordination Processor

The coordination processor (CP) handles the data base as well as configuration and coordination functions, e.g.:

- Storage and administration of all programs, exchange and subscriber data.

- Processing of received information for routing, path selection, zoning. charges,

- Communication with operation and maintenance centers,

- Supervision of all subsystems, receipt of error messages, analysis of supervisory result messages, alarm treatment, error messages, alarm treatment, error detection, error location and error neutralization and configuration functions.

- Handling of the man-machine interface.

CP 113 is used in medium- sized to very large exchanges. The CP113 ismultiprocessor and can be expanded in stages. It has a niaximuni call handiling capacity of over 1,000,000 BHCA. In the CP113 as shown in figure 7, two or more identical processors operate in parallel with load sharing. The rated load of n processors is distributed among n+l processors. This means that if one processor fails. operation can continue without restriction (redundancy, node with n+1 processors).

The Basic functional units of CP 113 are as follows :

— Base Processor (BAP) for operation and maintenance and call processing,

— Common Memory (CMY)-64 to 1024 MB in 4 memory banks consisting of 4 MB DRAM chips.

— Input / Output Controller (IOC) - 2 to 4 lOCs coordinate and supervise accessing of CMY by IOPs.

Input/output processors (IOP) - Various types of IOPs are used to connect the CP113 to the other subsystems and functional units of the exchange as well as to the external mass storage devices (EM i.e., MDD, MTD), the two O&M terminals (OMT), to OMC via data lines, etc. (Figure 8). Maximum 16 TOPs can be connected to one lOC.

16

17

Figure – 8 : Structure of Input / Output System with two IOCs

The other functional units of CP 113 are call proccssors (CAP) which deal only with call processing functions. Hardware wise they are similar to BAPs and form a redundant pool together with BAPs.

3.4.2 Other units assigned to CP (Figure 1) are:

• Message Buffer (MB) for coordinating internal message traffic between the CP, the SN, the LTGs and the CCNC in an exchange.

• Central Clock Generator (CCG) for the synchronization of the exchange and, where necessary, (The network. The CCG is extremely accurate (10-9). It can, however, be synchronized even more accurately by an external master clock (10-11).

MBs and CCG are equipped in two racks in maximum configuration.

• System Panel Display (SYPD) to display system internal alarms and the CP load. It thus provides a continuous overview of the state of the system. The SYP also displays external alarms such as fire and air-conditioning system failure for example. It is installed in the Equipment Room or in the Exploitation Room.

• Operation and Maintenance Terminals for Input/output. Two OMTs are provided for O&M functions.

• External Memory (EM), for

- Programs and data that do not always have to be resident in the CP,- An image of all resident programs and data for automatic recovery,- Call charge and traffic measurement data.

To ensure that these programs and data are safeguarded under all circumstances, the EM is duplicated. It consists of two magnetic disk devices (MDD), each of 780 MB capacity. The EM also has a magnetic tape device (MTD), for input and output. These units are mounted in a separate device rack (DEVD).

18

3. 5 Common Channel Signaling Network Control

The CCITT- standardized signaling system No.7 (CCS7) is one of the systems that is used for interexchange signaling in EWSD. To promote flexibility in; the use of this system a distinction is made between a message transfer part (MTP) and the user parts (UP). The user parts vary according to the specific application (e.g. TUP: telephone user part, ISDN-UP: ISDN user part, MUP: mobile user part). The common MTP functions in an EWSD exchange are handled by the common channel signaling network control (CCNC). The UP is incorporated in the software of the relevant LIG.

19

Figure – 9 : Common Channel Signalling Ntework ControlA maximum of 254 common signaling channels can be connected to the CCNC via either digital or analog links. The digital links are extended from the LTGs over both planes of the duplicated switching network and multiplexers to the CCNC. The CCNC is connected to the switching network via two 8 Mbps highways (SDCs). Between the CCNC and each switching network plane, 254 channels for each direction of transmission are available (254 channel pairs). The channels carry signaling data via both switching network planes to and from the LTGs at a speed of 64 kbps. Analog signaling links arc linked to the CCNC via modems.

For reasons of reliability the CCNC has a duplicated processor (CCNP) which is connected to the CP by means of similarly duplicated bus system. The CCNC consists of (Figure 9):

Upto 32 signaling link terminal (SILT) groups, each with 8 signaling links and

- One duplicatcd common channel signaling network processor (CCNP).

The functions of the CCNC depend on its position in a signaling link. In the originating or destination exchange in associated signaling, it operates as signaling point (SP) and in transit exchange in quasi-associated Signaling, it operates as a signaling transfer point (STP).

The CCNC, equipped in one rack can handle upto 48 signaling links. Equipments handling upto 96 signaling links can be equipped in additional racks.

20

Subscriber / Administration Facilities in EWSD

1 Rapid call set up— Abbreviated Dialing— Hotline Immediate— Hotline with Time Out

2. Call Restriction Services:— O/G Restrictions— Administration Controlled— Subs controlled— I/C Barring

3. Absent Subscriber Services— Immediate diversion— Diversion on no reply— to Operator— to a number— to announcement

4. Call Completion services— Diversion on busy— Call waiting— Call priority (originating & terminating)

5. Multiparty services— Conference call— Tele-meetirig

6. Alarm call booking— Casual— Regular (number of consecutive days)

7. Services to PBX— Direct dialing in (for different PBX capacitics)— Line hunting

8. Miscellancous Services— Malicious call identification— All calls— Special subscriber signal

9. Call charge services— Separate counters for Local Call charges, STD/ISD calls charges, Number of calls,

Service activation charges and Service usage charges— Transmission of meter pulses— Preventive meter observation (adjustable threshold)

21

System Data

Call-handling capacity No. of Subscriber lines max. 2,50,000No. of Trunks max. 60,000Switchable traffic. Max. 25,200 E

Supply voltage -48 V nominal direct voltage

Clock accuracy Maximum relative frequencydeviation: plesiochoronous 10-9,synchronous 10-11

Signaling systems All conventional signaling systems, e.g. CCITT R2, No.5, no. 7

Analog subscriber line Various loop and shunt resistance possible.and trunk accesses Push-button dialing, Multi-freq. Signaling

to CCITT Recommendation Q.23Rotary dialing : 5 to 22 pulse/s

1SDN accesses Basic access 160 kbps (2B+D+sync)B=64 kbps, D= 16 kbps

Primary rate access 2048 kbps(30B+D+sync.)

Digital trunk accesses 2048 kbps

Traffic routing Per destination max. 7 high-usage routes and one final routeScquential or random selection of idle trunk of a trunk groupNumber of trunk groups per exchange:

Max. 1000 incoming andMax. 1000 outgoing andMax. 1000 bothway

22

Call charge registration Periodic pulse metering,

AMA Automatic Message Accounting or DetailedBilling (CAMA, LAMA)

IARSTAT (Inter Administration Revenueaccounting and Statistics)

Max. 127 zones

Max. 6 tariffs per zone

Tariff switchover possible in 1 5-minute timing interva1sTransmission of communication data tocomputer center (output on tape also possib1e)

Space requirements Example: Exchange for 24000 lines units approx. 100m2

Environmental Ambient temperature 5°C to 40°Cconditions Relative humidity 10% to 8O%

23

ABBREVIATIONS

ALEX External Alarm module

APS Application Program System

ATE:TAutomatic Test Equipment for Trunks

B:… Bus for ..

BA Bus Arbiter

BAP Base Processor

CAP Call Processor

CCG Central Clock Generator

CCNC Common Channel signaling Network Control

CCNP Common Channel signaling Network Processor

CMY Common Memory

COUBConference Unit, Module B

CP Coordination Processor

CR Code Receiver

CTC Continutiy Check

DEVDDevice Rack

DIU30Digital Interface Unit for 2 Mbps digital trunks

DIUD Digital Interface Unit for DLU

DLU Digital Line Unit

DLUC Control for DLU

EM External Memory

24

EMSP Emergency Service equipment for Push-button subscribers.

GP Group Processor

GS Group Switch

GSL GS & LIU module

IOC Input / Output Control

IOP Input / Output Processor

ISDN Intergrated Services Digital Network

LDID Local DLU Interface Unit module D

LIU Link Interface Unit between LTG & SN

LTG Line / Trunk Group

M : … Module for…

MB Message Buffer

MDD Magnetic Disk Device

MTA Metallic Test Access

MTD Magnetic Tape Drive

MTP Message Transfer Part

MU Memory Unit

OMT O & M Terminal

PDC Primary Digital Carrier

R:… Rack for …

RCU Remote Control Unit

S:… Shelf for …

SASC Stand Alone Service Controller

25

SC-MUX Signal Converter Multiplexer

SGC Switch Group Control

SILT Signaling Link Terminal

SLCA/D Subscriber Line Circuit Analog / Digital

SLMA/D Subscribe Line Module Analog / Digital

SLMCP Processor for SLM for DLU

SN Switching Network

SPMX Speech Multiplexer

SSG Switch Stage Group

SU Signaling Unit

SYPD System Panel Display

TA Terminal Adapter

TOG Tone Generator

TSG Time Stage Group

TU Test Unit

UP User Part

26

Details of EWSD Exchanges Commissioned/PlannedIn the Network

27

28

DIGITAL LINE UNIT

What is inside ?

1. Introduction & DLU feature’s

2. Structure

2.1 DLUSystem

2.2 Ringing and Metering Voltage Generation

2. 3 Bus System

2. 4 Periphery2.5 Direct Current Converters

2.6 Software

2.7 Rack and Module frame layouts

3. Remote Control Unit

4. MML commands for DLU

5. O& M Aspects

Annex. 1 . DLU creation sequence

Annex. 2 : Call setup under normal/emergency operation

Exercises

Digital Line Unit

29

1.0 Introduction

Subscriber lines and PBX lines in EWSD are connected to digital line units (DLU).

The DLUs can be operated locally in an exchange or remotely (Fig.l).

The DLUs are connected to the Switching Netvork via LTG (B-function A DLU is connected to an LTG by 2 Mbps Primary Digital carriers (PDC However, the local DLUs (the DLUs located in the main exchange ) are connected to the LTG(B) by 4 Mbps carriers.

For security reasons, a DLU is connected to two LTGs. A subset of CCS according to CCITT is used for signaling between a DLU and the Group Process (GP) in the two LTGs.

Remote DLUs are installed in the vicinity of groups of subscribers. The resultant short subscriber lines and the flexible concentration of subscriber traffic to the exchange Onto digital transmission links makes for an economical subscriber line network with optimum transmission quality.

The following are the important DLU features:

• Connection capacity of a single DLU : up to 952 subscriber lines (depending on type of subscriber line (analog/ISDN),functional units provided and required traffic values.)

• Traffic handling capacity : up to 100 Erlangs• Connectivity : Analog subscriber lines with

- rotary / DTMF dialing - call charge indication with 16/12 kHzas well as access lines for - Coinbox telephones - analog PBXs with/without DID - small and medium-sized digital PBXsSubscriber lines for - ISDN basic access

30

Figure – 1 : Application & Connections via Primary Carriers (PDCs)

• Growth capability in small modular steps:

31

4,6 or 8 subscriber line circuits (SLCs), according to module type.

• Connection to line/trunk group G (LTGG(B)) via one, two or four PCM3O multiplex lines (primary digital carriers, PDC). The local connection to LTGG can be realised via two 4096-kbps multiplex lines.

Maximum number of channels available for transmission of user information between a DLU and two LTGs is 120.

• Common channel signalling (CCS) between the DLU and the LTGs. TS 16 on PDCO and PDC2 used for this purpose.

• High operating reliability

- due to the connection of the DLU to two LTGs

- duplication and load sharing of DLU modules handling central functions( DLU system 0 and 1)

- continuous self-tests

• Full availability between the connected subscriber lines and the channels to the exchange

• All EWSD features, regardless of whether the DLU is operated locally or remotely.

• Identical equipment in all DLUs, both for local and remote operation.

• Integrated test unit (TU) for automatic and manual testing of subscriber line circuits, subscriber lines and analog telephone sets

• Metallic test access (MTA) giving external subscriber line testing systems access to the analog subscriber lines connected to the DLU

• DLU emergency operation (in the event of total failure of the transmission routes to the main exchange)

32

• Remote control unit (RCU, Sec. 3) used for remote operation and consisting of upto six remote DLUs. Each R-DLU of the remote cluster has an SASC module (Stand-alone Service controller) for emergency operation.

2.0 Structure

ln the majority of cases, the modules belonging to a DLU are arranged in moduleframes, with two rows of modules. Module frames with one row of modules are only used in 2130-mm racks. In the DLU a row of modules in a module frame is termed as a shelf A shelf is subdivided into a left-hand and a right-hand half-shelf (as seen from the module side of the module frame).

To understand the architecture of the DLU, the DLU structure will be discussed in the following sequence (Refer Fig 2):

• DLU system comprising of central cards,

• Ringing & Metering Voltage Generation,

• Bus system comprising of

- Control Network for processors

- 4096-kbits/s network for speech signals

• Peripheral cards which include Line cards and Test cards,

• DCCs, i.e., Direct Current Converters

2.1. DLU System

A DLU system contains the following functional units:

(a) a control for digital line unit (DLUC),

(b) a digital interface unit for DLU (DIUD),

(c) a clock generator (..CG) &

(d) two bus distributor modules (BD..).

A DLU system is a failure unit which is duplicated in the DLU (Fig.2). Both DLU systems are housed together in a module frame (Fig. 10-a).

33

The DLU system 0 (DLUCO, DIUDO,..CGO and BD.0) are contained in the upper shelf (shelf 0) of the module frame and the DLU system 1 (DLUCI, DIUDI,..CG1 and BD.. 1) are contained in the lower shelf (shelf 1).

The functional units DLUC, DIUD and ..CG are also referred to as central units. If a fault occurs in a central functional unit of one of the DLU systems, normal call handling is still possible via the other DLU system.

DLU Controller (DLUC)

For security reasons and to increase throughput, there are two DLUCs in the DLU. They work independently in a task sharing mode. If one DLUC fails, the second DLUC can handle the tasks alone.

The DLUC controls the sequence of DLU-internal functions and either distributes or concentrates the signaling between the subscriber line circuits and the• DLUC. The DLU-internal control network connects the DLUC with the shelves. All functional units equipped with their own microprocessors are addressed through this control network.

The units are polled cyclically by DLUC for messages ready to be sent, and are accessed directly for the transfer of commands and data from DLUC.

The DLUC carries out test and supervision routines to detect errors.

LEDs on the DLUC indicate the operating mode & the status of the PDCs.

34

Figure – 2(a) : Simplified Block Diagram of DLU

35

Figure – 2(b) : Detailed Block disgram of the DLU

36

Digital Interface Unit for DLU (DIUD)

The DIVD has two interfaces tbr the connection of two PCM3O multiplex lines (PDCs) connecting the DLU with the LTG. Either balanced or coaxial cables can be connected. A total of 128 channel pairs are available between the SLCAs and the DIUDs

- 120 channels for the transmission of user information.

- 8 channels for transmission of tones for routine loop tests as well as audible tones during emergency service.

The following are the important functions of DIVD

1. Takes the control information arriving from the LTG from channel 16, of a PDC (DIUD0 takes the control information from PDCO, DIUDI from PDC2). The DIUD forwards the incoming control information from this LTG to the partner DLUC (i.e., the DLUC belonging to the same DLU system as that of the DIUD.). In the opposite direction the information coming from partner DLUC is inserted in channel 16 of the same PDC and transmitted to the LTG.

2. Provides the interfaces to a DLU-internal 4096-kbitts network to the individual shelves. The user information is distributed to and from the SLM modules via this 4096-kbit/s network.

3. Derives a signal for synchronization of the clock generator from the line clock of the PDC.

4. Performs test and supervisory routines and detects any occurring errors.

5. The channel contents of the PDC with CCS are forwarded to the even-numbered channels of the 4096-khit/s network, the channel contents of the PDC will cut CCS to the odd channels. (Refer Fig. 3).

6. A test loop, is switched via the DIUD for the cross office check (COC) conducted by the LTG.

7. LEDs, in the module faceplate indicate the operating mode of the DIUD and the PDCs.

Digital Interface Unit for Local DLU Interface, module D (DIU : LDID)

Usually the local DLU is connected to the LTG via a single 4 Mbps interface having 64 time-slots instead of 2 independent PDCs.

37

For conecting a local DLU to LTG(B), the interface in the: DLU is. DIU:LDID in place of DIUD. The DIU:LDID has 4096-kbit/s interface. For such a connection a balanced copper line is used. The DIU:LDID handles the transmission: of the contents of 60 user channels and a control information channel via a single 4096-Mbps. multiplex line (instead of via two PDCs). The main tasks of the DIU:LDID are similar to those ofthe DIUD.

Figure – 3 : Functional Unit DIUD :Multiplexing the PDCs into a 4096 kbit/s network

And demultiplexing of channel 16 to DLUC

38

• Bus distributor module with clock generator for DLU (BDCG)

The clockgenerator (..CG) generates the system clock of 4096-kHz required by the DLU and the associated frame synchronization pulse. For security reasons the clock generator is also duplicated. The two clock generators work according to the masterslave principle. Under normal operating conditions the clock generator designated as the master is active while the slave generator is in standby mode.

The master supplies both DLU system with clock signals. If the master fails, the system switches over to the slave generator which then supplies both DLU systems with clock signals.

The clock generator receives a synchronizing signal from the DIUD in the same shelf; the DIUD derives this signal from the line clock of the related PDC.

The functions of the bus distributor (BD..) are described in (the following sections on ‘Ringing & Metering Voltage Generator’ and ‘Bus System’ ( Sec. 2.2 and 2.3).

2.2 RINGING & METERING VOLTAGE GENERATOR

The ringing and metering voltage generator (RGMG) generates the sinusoidal ringing and metering voltages required in the DLU for analog subscribers, as well as a synchronizing signal for ringing the subscribers.

Several different frequencies can be set for the ringing voltage by means of switches. Another switch allows two different voltages to be set for each frequency selected.

Two diflerent frequencies (12 or 16 kHz) can be set for metering voltage by means of a switch. The metering voltage cannot be changed.

The ringing and metering A-C voltage are monitored for undervoltage. If the voltage drops below the minimum value permitted, an alarm is signaled. Each BD... unit can switch over to another RGMG which then supplies the entire DLU wIth ringing and metering voltage.

From each RGMG, a ring bus system is used for the distribution of ringing and metering vo1tage.

RGMGO supplies ringing and metering voltage to all the mounting locations for SLMs in the left-hand half-shelves (SLMO...7) through the ring bus system 0 and the BD.. units in these half-shelves. RGMGI supplies ringing and metering voltage to all the mounting locations for SLMs in the right-hand half-shelves (SLM8..15), through the ring bus system 1 and BD... units in these half-shelves during normal operation. If a fault occurs in one of the RGMGs, the other RGMG takes over the entire load. (Refer Fig 4);

39

The ringing voltage is fed to the BD.. units over a short-circuit safety circuit and is distributed unamplified to the’ SLM mounting locations in the relevant half-shelf.

The metering voltage is forwarded to an amplifier with balanced high-impedance input in the BD.. units and distributed unbalanced and with , low impedance in the relevant half-shelf

Figure – 4 : Distribution of the Ringing Current

40

2.3 BUS SYSTEM

Information is exchanged in the DLU via a duplicated bus system (Fig 2). The exchange of information between the DLU system 0 and the peripheral units takes place via bus system 0, between the DLU system 1 and the peripheral units via bus system 1. If one bus system fails, the other bus system is used for the exchange of information from both DLU systems. Each bus system includes a control network and a 4096-kbit/s network.

• Control network ( For communication between DLUC and the processors o1 the peripheral modules)

Control. network 0 and 1 are associated with the DLUCO and DLUC1 respectively. ,A DLUC has eight interfaces (one for each possible shelf), from which the control lines of the network lead to the BD..modules in the individual shelves. From the BD.. units the control network branches further in groups to the mounting locations of functional units with microprocessors.

Control network 0 and 1 lead to all appropriate mounting locations in the shelves, so that if one of the control networks fails, the other one can serve all mounting locations. The signals are regenerated in the BD.. units and fanned out through further outputs to the periphery. Similarly incoming signals from the periphery are concentrated onto fewer lines. This network structure limits the fault penetration range.

The control networks convey control information, i.e., subscriber signaling and commands from the DLUC to the SLMs, and transmit subscriber signaling and messages in the opposite direction. In both directions the bit rate of the control networks is,187.5 kbit/s, i.e., effectively approximately 136 kbit/s.

• 4096-kbit/s network (For 64 kbps user channels )

The 4096-kbit/s networks 0 and 1 are associated with the DIUDO and DIUD1 respectively. A DIUD has eight interfaces (one for each possible shelf), from which the lines of the network lead to the BD.. modules in the individual shelvs. The network structure is identical to that of the control network.

Both 4096-kbit/s networks have 64 channels for each direction of transmission with a bit rate of 64 kbit/s. The user information is transmitted in these channels to and from the SLMs. For the transmission of user information a fixed relationship exists via the DIUD between the channels of the 4096-kbit/s networks and the chartnels of the PDCs.

41

2.4 PERIPHERY

The subscriber line modules (SLM) build the interface to the subscribers. The SLMs are accommodated partly in shelves 0 and 1 with the central units and partly in shelves 2.. .7 in the extension module frames.

The subscriber line modules, analog (SLMA) serve to connect analog subscribers to the system. Digital subscribers are connected via subscriber line, modules, digital (SLMD).

Subscriber line module, analog (SLMA)

The following subscriber line modules are used for the connection of analog subsribers:- SLMA:COS, for ordinary subscribers- SLMA:CMRL, 12-kHz/16-kHz meter pulse injection, line reversal and loop open- SLMA:CSR, with silent reversal for coinbox telephones- SLMA:DID, for direct inward dialing- SLMA:FPB, feature programmable

The SLMAs.... can have four, six or eight analog subscriber line circuits (SLCA...), which are controlled by the processor (SLMCP). One analog subscriber can be connected to the DLU via each subscriber line circuit. The SLCA. . ..contains the necessary indication and feeding circuits as well as the analog-to-digital and digital-to-analog conversion for voice information.

Figure – 5 : Subscriber Line Module, Analog (SLMA)

42

Important Functions if the SLMA are :

• High impedance line monitoring for detection of events in the idle state

• Constant current injection with adjustable current values in the call condition with loop closure and short-to ground detection

• Receivingof pulse dialing

• Forwarding of DTMF dialing to LTG

• Balanced ringing injection, Ring tripping when subscriber answers

• SLCA with integrated range extension

• Connection of the subscriber line and subscriber circuit side to a test multiple

• Proteétion against overvoltage and external voltage

• DC decouping of the voice signals

• Adjustable relative transmit and receive levels

• Adjustable2-wire impedence

• Coding/decoding of speech signals according to A-law or -Law with filter function

• Fulfilling the CCITT transmission requirements

• Pre-processing of signals in the SLMCP

• Hard reversal of speech wires

• Silent reversal

• Single-wire disconnection of supply voltage

• Loop open

• Transmission of dial pulses

• Injection of meter pulses

• Interface to the 4096-kbit/s networks

• Interface to the control networks

Subscriber line module, digital (SLMD)

The subscriber line module, digital (SLMD) is used to connect digital subscribers. A rnodule has eight subscriber line circuits, digital (SLCD), which are controlled by a processor. Each subscriber line circuit provides a basic access for ISDN terminals for ome subscriber via the network termination (NT, Fig 7)

43

The data are transmitted between SLMD and NT via a balanced 2-wire line with a total data rate of 160-kbit/s. The total data rate is made up of 144-kbit/s user information and 16 kbit/s for synchronization, monitoring and diagnostics. The user information available to the subscriber at 144 kbit/s offers each subscriber simultaneous access to two B-channels each with 64 kbitls for bit-transparent transmission of information (voice, text, data and image) and access to a D-channel with 16 kbit/s. The D-channel is used to transmit, among other things, the signaling between subscriber and exchange and to transmit low transfer rate data (e.g. packet data, telemetry data).

Figure – 6 : Subscriber Line Module, Digital (SLMD)

Important functions of the SLMD are

• Interface to the subscriber line(Feeding of the subscriber line circuit with -60 V and for range extension with -93 V or -97 V.

For test purposes, connection of the subscriber line citcuit and the subscriber line to the test unit (TU) via the test matrix)

• Remote power feeding of the NT and digital telephone following failure of the local power network

• 2-wire/4-wire conversion with adjustable line building-out network

• Echo compensation for fully duplex transmission on the 2-wire subscriber line.

• Conversion of the data received from the subscriber in 4B/3T or 2B/1Q code to binary code and level alignment

44

• Conversion of the data to be sent to the subscriber from binary code into 4B/3T or 2B/IQ code and.level alignment• Signalling transmission according to the D-channel protocol

• Assignineiit of the incoming information from the subscriber in the B1, B2 and D channels to the allocated time slots of the 4096kbit/s network

• Assignment of the information received via the various time slots of the 4096-kbit/s network to the BI. B2 and D channels of the subscriber line.

Figure – 7 : Terminals Connected to ISDN Basis Access.

45

Test Unit

The test unit (TU) consists of two modules - FMTU and LCMM. These two modules can be plugged into mounting locations for SLMs in the module frame with central units, i.e. F:DLU(A).

The test unit is provided in the DLU to test subscriber tclephones. subcribers lines and subscriber line circuits (SI .Cs). It can be conected: to each subscriber line or each SLC via a test bus. The test relays for metallic access to the items to be tested are an integral part of the SLCs.

Testing of the subscriber lines connected to the DLU is controllcd from the line workstation (LWS). The LWS can be located either centrally in the OMC or locally in the exchange. A special user program (TLFI) in the GP of the LTG acts as the interface between the TU and the LWS. The program TLFI controls the TU and therefore the subscriber line test in accordance with the inputs. During such test, the GP and TU exchange commands (GP to TU) and results (TU to GP) via CCS channel pair 16 of one PDC and via one DLUC.

In addition to the LWS, the subscriber line measuring system (SULIM) can also be used to control testing of analog subscriber lines. The SULIM measuring boards are located at the DLU site, in exchange or in the OMC. The user program TLFB in the GP of the LTG acts as the interface between the TU and the SULIM measuring boards.

More details on Line Work Stations and SULIM will follow under Obj. 4.4 (Line and Trunk Testing).

Metallic Test Access ( MTA & LTBAM)

The metallic test access (MTA) allows external subsriber line test systems to access the analog subscriber lines connected to the DLU. The MTA contains measurement and signaling interfaces. The measurement interface provide ides the metallic access for the local external test equipment and measuring instruments connected to EWSD. Activation and deactivation of the measurement interface is controlled via a signaling interface.

To connect external test equipment, a Loop Test and Bus Access Module (LTBAM) is required in each DLU. This module provides the link between the subscriber line module SLMA and the external test equipment. A meditation function PC (MF-PC) with interface card is also necessary.

46

Stand-along service control (SASC) R-DLU

During emergency operation the stand-alone service control (SASC) is required in remote DLUs for the communication between the connected analog, ISDN and CENTREX subscribers. SASCs are also used in each DLU of a remote control unit (RCU, Section – 3).

Emergency service equipment for push-button subscribers (EMSP) R-DLU

DLU can be equipped with an EMSP instead of an SLMA. Normally a maximum of two EMSPs can be provided. Each EMSP contains THREE code-receiver circuits.

Under normal operating conditions an LTG receives the dialed information from DTMF subscribers and evaluates it. In emergency service, pushbutton receivers are required in the DLU itself for these subscribers. These pushbutton receivers are contained in the EMSP modules.

External alarm set R-DLU

The external alarm set (ALEX) is used to relay alarms from external devices (e.g., air conditioning, power supply, fire extinguishers etc.) to the SYPD. Minimum one ALEX module is required per remote cluster of DLUs. The ALEX can connect upto 16 external alarms to the main exchange.

A specific fault printout can be output by the system for every external DLU alarm. The commands for defining these fault printouts is contained in the MMN for SYP ( (register INTRO ). The same document also describes the level definition of these alarms. The pin assignments for the ALEX are described in MMN for DLU (register TAB, chapter LED).

2.5 Direct Current Converters

The DLU power supply is decentralized. For each half-shelf in the module frame there is a separate direct-current converter module (DCC). If a DCC fails, the consequences are relatively minor, as only one half-shelf is affected.

The DCC modules supply all the operating voltages required in the shelf (including the voltages required for any range extensions). The voltages generated are monitored for undervoltage, and some also for overvoltage. If the specified tolerances are exceeded, an alarm is triggered and the D/C converter is disconnected electronically. All voltage outputs of the DCC modules are short-circuit protected.

47

If the module DCC0-1 or DCC1-1 fails (i.e. DCCs in frame A), the respective DLU system fails. The DLU system not affected then takes over the work of the failed system.

The voltage for the two DCCs in a shelf is fed via a common fuse in the fuse panel. The exchange voltage supplied is unfiltered.

The voltage for the subscriber line modules (SLM) in each shelf is fed via a fuse in the fuse panel. As far as the power supply is concerned, the subscriber line modules are termed load circuits. The voltage supplied is filtered.

2.6 Software

The application program system (APS) of an EWSD exchange also contains the necessary software for the DLU. This software comprises:

• DLU data

• DLU data access programs

• Maintenance programs

• Safeguarding programs

• Call Processing programs

• Operation and maintenance programs

At initial system start the coordination processor (CP) initializes itself and loads the complete APS. Then the CP loads the group processors (GP) in the line/trunk groups with their programs and data. The LTGs which control the DLUs also receive additional programs and data. When loading of the LTGs is completed, the CP sends configuration commands to the LTGs. These activate the LTGs and they can start to supply their periphery with data.

The DLUCs send load requests to the LTGs continuously via the common-channel signaling link. Within the DLUs, the Processors in the SLM cards (SLMCP) send load requests to the DLUCs.

The LTGs acknowledge the requests of the DLUCs and load them with data. When the DLUC is loaded, the LTGs send corresponding messages to the CP.

48

Figure – 8(a) : Loading of DLU-Software when DLUC / DLUMOD are configured to ACT

The CP sends configuration commands to the DLUC. In this way the DLUCs and consequently the DLUs as a whole are activated. Within the DLUs. the load requests of the SLM processors can now be acknowledged. The DLUCs pass on all the necessary data to the SLM processors. As soon as the processors have received all the necessary data, including the configuration data, call processing can begin.

Irrespective of whether a system initial start concerns the initial loading of the software to the system or a system recovery, the procedure for loading the software is identica! (Fig. 8b). For initial loading of the software to (the system the CP loads the APS from magnetic tape, whereas for a system recovery the CP loads the APS from magnetic disk.

If an initial start (recovery) has to be performed for only part of the system, e.g. an LTG initial start, only the affected LTG is loaded with programs and data from the CP. This is followed by the loading of the DLUCs and SLMCPs in the DLUs connected to this LTG as previously explained.

49

Figure – 8(b) : Load path for programs and date

DLU Software distribution over different processors

The DLU software is mainly stored as distributed firmware. The firmware is contained in

- the DLUP and lOP in each DLUC

- the SLMCP in each SLMA

- the DIUD controller in each DIUD

- each EMSP module

- each BDCG

- each ALEX module

- each module of the TU

After power-up, the DLU processors carry out the initialization tasks in the units listed above. The DLU is operational when it has received the appropriate semipermanent data from the LTG and when all data are loaded in the SLCAs.

The software in all the DLU processors operates in a similar manner. As an example the software in a DLUP is described here. The DLUP software has three operating levels:

- start level- real time level- task level

Following the initialization tasks in the DLUC and the setup of communication with the group processor in the LTG the DLUP software normally oeprates in the task level. The master scheduler endless loop determines the tasks to be processed according to their priorities. Service routines, general routines and user programs are available in the main routines in the task level. The interrupt programs are real-time programs which have to be run immediately. To enable this the program

50

running in the task level is interruped and the interrupt program executed. After interupt program completion, the interrupted task level program is continued.

Before DLU emergency service is begun new initialization has to be performed in the DLUP before returning to the task level. The setting up of internal connections can then be controlled from the task level At the end of service another initialization is carried out before returing to the task level and normal I operational Service.

Example of functions of other DLU processors are as follows:

• IOP (in the DLUC as well) Scanning the SLMCPs storage and distributionof control information.

• SLMCP Handling subscriber signalling Handling DLUC commands

• DIUD Controller Controlling the 4096-kbit/s networkControlling the common signaling channelGeneration of tones

• Processor in the EMSP Evaluation of DTMF dialing informationduring emergency operation

• Processor in the BDCG Contrlling the 4096 kbit/s networks

• Processor in the ALEX Monitoring the alarm statesForwarding alarm state transitions

• Processor in the TU modules Junction testing Measuring voltages, impedances and capacitances.

2.7 Rack and Module frame layouts

The DLUs are accommodated in racks. Fig 9 shows different layout options. Only three types of module frames are used fbr the entire DLU program [F:DLU (A), F:DLU(B) & F:DLU(C), Fig 10]. The module frames contain either one or two rows of modules that are referred to as “shelves” in the following figures.

The DLUs are created and configured using MML commands (see Annex. I). These MML commands apply to groups of functional units or to individual modules (Fig 1 0). Data entered during creation generate a memory map of the previously unknown functional unit in the coordination processor. When configuration takes place the functional unit is placed in the desired operating state (e.g., active).

51

Figure – 9 : RLU (2450-mm rack for DLU)

52

Figure 10(a) : F:DLU(A) – MODULE FRAME (A) for upto 176 Subjs Lines.

Figure – 10(b) : F:DLU(B) – Module Frame (B) for upto 256 Subs Lines

53

3.0 Remote Control Unit (RCU)

The remote control unit RCU (Fig 12) can consist of up to six DLUs. Each DLU of the RCU contains a stand-alone service controller (SASC) which can be plugged in place of two SLMs. During normal operation the connection between the subscribers served by the RCU are established via the EWSD exchange.

3.1 Emergency service for remote DLU

(a) Failure of all connections to the exchangeIn this case; the SASCs of the DLUs control the connection setup between the DLUs of the RCU and also internally in their own respective DLU. During emergency service, all the subscribers connected to the RCU can communicate with one another. -

(b) Fuifure of the connections of one or moreDLUs (but not all) to the exchange

In the case of the failure of the connections to the cxchange of one or more DLUs the subscribers connected to these DLUs can communicate with one another. The SASCs of the. DLUs once again take over the control of the connection setup. The DLUs of an RCU not operating in the cmergcncy service continue functioning in normal operation.

3.2 Rack and module frame layout

The information and illustrations given in Section 2, e.g., the rack and module frame R and C layouts, also apply to the DLUs in the RCU. Fig 11 shows the module frame A equipped with an SASC.

54

Figure – 11 : F:DLU(A) for RCU

55

Figure – RCU interfaces

56

4.0 MML Commands forDLU

4.1 Overview :

CR DLU CR DLUMODDISPDLU DISP DLUEQ DISPDLUMOD DISP DLUPORTSEL SEL DLUPORTSTAT DLU STAT DLUEQ STAT DLUMOD STAT DLUPORTCONF DLU CONF DLUEQ CONF DLUMOD CONF DLUPORTDIAG DLU DIAG DLUEQ DIAG DLUMOD DIAG DLUPORTCAN RCU (Cancel RCU)EXT RCU (Extend RCU)RED RCU (Reduce RCU)

Line Testing Commands

TEST DLULC : Line test (using Eqpt. Number)

TEST SLC : Line test (using Directory number)

ENTR TST SCHED : Enter Test Schedule

DISP LN LCKOUT : Display numbers of PG condition

57

4.2 Identification of important DLU parameters :

DLU no. : 10 to 2550 (insteps of 10)

LTG no. : tsg-ltgWhere tsg = 0 to7 (Time Stage Group on which the associated LTG isterminated)Tsg = 1 to 63

OST : Operating State (ACT / MBL / CBL)

Shf-mod : identification no. of Subscriber Line ModulesShf = Shelf no. (0 to 7)Mod = Module no. (0 to 15)

Shf-dcc : Identification no. of DC ConvertersDcc = DCC Module no. (0 or 1)

RCU ID : 654321

RCUMBR : yyyy-zWhere yyyy = DLU no. (10 to 2550)Z = Relative no. of DLU within the RCU (1 to 6)

58

MML Commands for O & M

For MML purpose, the DLU is subdivided into the following logical configuration units :

* DLU system (DLU SYS)

* DLU equipment (DLU EQ)

* DLU module (DLU MOD)

* DLU port (DLU PORT)

DLUSYS consists of : DLUCDIUD with CCSPDCDIU : LTG with CCS and SILCDIU :LTG without CCS

DLUEQ consists of : RGMG – O and RGMG –1DCCs

DLUMOD consists of : SLMsBDCGFMTU andLCMM (Test Unit)SASC, EMSP and ALEX (in R-DLU)

DLUPORT refers to : Subscriber line circuit, SLC(HW for individual subscribers on the SLM)

59

(1) Interrogating the DLU connectivity :DISP DLU : DLU = x :

DLU Shelf DLUC-0 DLUC-110 A 0-1-0-2 0-2-0-220 A 0-1-2-4 0-3-0

30 A 0-2-2 0-3-1

STAT DIU : LTG = 0-1 DIU = x:LTG DIU DIUTYP Applic OST LTG OST DIU OST PCM0-1 0 D30 CCSLDI ACT ACT ACT0-1 1 D30 CCSDLU ACT ACT ACT0-1 2 D30 EXTLDI ACT ACT ACT0-1 3 D30 EXTDLU ACT ACT ACT

STAT DIU : LTG = 0-4, DIU = xLTG DIU DIUTYP Applic OST LTG OST DIU OST PCM0-4 0 D30 CCSRCA ACT ACT ACT0-4 1 D30 CAS CAS ACT ACT ACT0-4 2 D30 CCS CCS ACT ACT ACT0-4 3 D30 CAS CAS ACT ACT ACT

(2) Status Interrogation STAT DLUSTAT DLU EQSTAT DLU MODSTAT DLU PORTSTAT RCU

60

Interrogating DLU System :

STAT DLU : DLU = x (dlu no.) ;

STAT DLU Exec’dDLU SIDE –0 SIDE –1

Access AccessDLUC-OST degrading LTG LTG-OST DLUC-OST degrading LTG LTG-OST10 ACT NON 0-1 ACT ACT NON 0-2 ACT20 ACT NON 0-1 ACT ACT NON 0-3 ACT30 ACT NON 0-2 ACT ACT NON 0-3 ACT

Interrogating DLU Equipment :

STAT DLUEQ : DLU = 10, DCC = x-xDLU DCC OST Access – Degrading

Side –0 Side – 110 0-0 ACT NON NON

0-1 ACT NON NON1-0 ACT NON NON1-1 ACT NON NON2-0 PLA NON NON2-1 PLA NON NON& so on upto 7-1

STAT DLUEQ ; DLU = 10, RGMG = xDLU RGMG OST Access – Degrading

Side – 0 Side –110 0 ACT NON NON

1 ACT NON NON

61

Interrogation DLU Modules :

STAT DLUMOD ; DLU = 10, MOD = 0-x for interrogation shelf – 0 modules

DLU DCC TYPE OST Access-DegradingAside –0 Side – 1

10 0-0 SLMACOS ACT NON NON

0-1 SLMACOS ACT NON NON

0-2 SASC ACT NON NON

0-3 SLMACMRL ACT NON NON

0-8 BDCG ACT NON NON

0-11 FMTU ACT NON NON

012 LCMM ACT NON NON

0-15 SLMDB ACT NON NON

STAT DLUMOD : DLU = no, MOD sft –mod for a moduleDLU = no, MOD – shf-mod && shf-mod

For a range of modules

DLU = no MOD = x-x for all modules of a DLU

Interrogating RCU Operating Status :

STAT RCU ; Rcum = Gomti.

RCUMBR side – 0 Side – 1 Side – 0DLUCO Access-Degarding OST Degrading

20-1 ACT NON ACT NON ACT NON

30-2 ACT NON ACT NON ACT NON

100-3 ACT NON ACT NON ACT NON

50-4 ACT NON ACT NON ACT NON

62

RCULNK

RCUMBR – RCUMBRStatus

20-1 30-2 ACT

20-1 100-3Act

20-1 50-4 ACT

30-2 100-3ACT

30-2 50-4 ACT

100-3 50-4 ACT

The command displays status information for all DLUCs & SASC modules and also the status of all the SASC links within an RCU.

63

(3) Configurations

Configuring the DLU System

An active DLU system may be configured to MBL for maintenance only by way of CBL. Such configuration is necessary when, for example, subunits of the DLU (DLU modules, DLU equipment) are configured to DST by the system. If the DLU system is in DST or if the LTG has no ACT/CBL operating state, the system can be configured directly to MBL. If this occurs, no STARTED message or warning will be printed out. –

Example: Input for configuration from ACT to CBL, (LTG = ACT/CBL): -

CONF DLU : DLU = no, DLUC0=y, OST = CBL;

Configuring DLU Equipment

- DLU equipment includes the current converter modules DCC and the Ringing voltage generator modules RGMG. One of the two RGMGs can be configured directly from ACT to MBL and MBL to ACT.

CONF DLU EQDLU = no, RGMG = 0 or 1, OST = ost;

A DCC can be configured to MBL only if the dependent modules in the corresponding half-shelf are not ACT. -

Configuring DLU Modules

Input for configuration from ACT to CBL and then to MBL:

CONF DLUMOD DLU=no, MOD=shf-mod, OST=CBL;DLU=no, MOD=shf-mod && shf-mod, OST=CBL; for a module area

If a module or module area ACCESS-DEGRADING = DST over both sides, then a direct configuration to MBL is possible. With this configuration no caution is output.

Modules which are not used for switching operations can be directly configured from ACT —> MBL (e.g., ALEX, TU-Module).

64

(4) Diagnostics

Fault analysis in the DLU detects faults which occur within the DLU, while fault analysis in the LTG detects interface faults. Fault analysis in the CP makes the final interpretation of error messages arriving from both LTG and DLU.

The diagnostics determines the location of the fault within the faulty unit, making rapid fault clearance possible.

Requirements for Starting the DLU Diagnostics:

A diagnostics can be carried out only if associated peripheral units are in the following operating states:

- LTG* =ACT or CBL

- MB =ACT

- SN = ACT or STB

The basic functions in the CP must also be intact.

Diagnostics of the entire DLU (both DLU systems) is implemented only on initial start-up, and is these not described in the MMN.

Diagnosing a DLU System

The DLU system concerned must be in MBL. Either the central and partially central sections, only the central sections, or only the PCM bus are tested, according to the input command.

DIAG DLU : DLU=no, DLUC0 = y;

DLU = No, DLUC1 = y;

Diagnosing the DLU Equipment

A diagnostics of partially central equipment requires that both the DLU systems be in ACT or CBL, while the unit to be diagnosed must be in MBL.

DIAG DLUEQ: DLU=no. DCC = shf-mod:

: DLU=no, RGMG=,no:

Diagnosing the dlu Modules :

65

A diagnostics of the DLU modules (SLMs) requires that at least one of the associated DLU systems be in ACT or CBL, while the module to be diagnosed must be in MBL. DIAG DLUMOD : DLU = no, MOD = shf-mod;

: DLU = no, MOD = shf-mod && shf-mod;For a module area

(4) Maintenance of RCU

Creation of RCU

CRRCU: RC = <rcu>,

RCUMBR = <dlu> - <mbr> & ...& <dlu> - <mbr>;

Example: Create an RCU at Rajnagar using DLU nos. 20, 30 and 500. -

CRRCU :RCU = Rajnagar

RCUMBR = 20-1 & 30-2 & 500-3;

DISP RCU : RCU = <rcu>

DLU = <dlu>

STATRCU : RCU = <rcu>;

Modifications of RCU:

EXT RCU [Example ; To add DLU 150 in the above cluster

EXT RCU : RCU = Rajnagar,

RCUMBR = 150-4;

RED RCU: Reduce RCU (Take out and R-DLU from the cluster)

CAN RCU Cancellation of the cluster

66

5.2.4 Tests

For details of tests using the test unit TU, see MMN: TE, register TU.

5.0 O&M ASPECTS (For more details, P1. refer MMN.DLU-IN)

5. 1 General hints for HW-Maintenance

Operational Status OST

The availability of the di different units is determined by their operational status. The basic slates are as follows

1. The unit is ready for operation

2. The unit is not ready for operation

3. The unit is not present

This information is stored in the CP and sometimes in the effected unit itself or in the next higher ranking unit (e.g. GP knows OST of connected DLUC). It can he displayed by STAT-Commands.

In the DLU and the CCNC a differentiation is made between the actual status and the target status of the units.

1. Ready for operation means that the unit has one of the following operation status

- active: ACT

- standby : STB

(Units which are not duplicated always have the operational status ACT(e.g. MTD, LTG, DIU, SYP).

For duplicated units there are always two possibilities

— both units arc in the operation status ACT (e.g. MDD, MU, MB)

— one unit is in the status ACT, the second unit is in the status STB:(e.g. SN. MCH, CCG)

2. Units which are not ready : The following operation states arc possible

- maintenance blocked : MBL

- conditionally blocked : CBL

67

- defective : UNA

- not accessible : NAC

(a) MBL : A unit that should be blocked in order to execute maintenance tasks (e.g. during the fault clearance), must be configured to MBL.

(b) CBL : If a non-duplicated unit of the switching periphery is to be made MBL. (e.g. LTG) the relevant unit must first be configured to CBL. In CBL status. the unit can no longer be used for new connections. As soon as all subscribers or trunks have the status ‘idle’, a print out is given at the OMT and this unit can then be configured to MBL.

For example. LTG. being a non-duplicated unit must be configured first to CBL before configuring to MBL. After CBL acknowledgment on the OMT the LTG can be configured to MBL.

(c) UNA: A unit ready lor operation which is recognized by the safe guarding SW as faulty is taken out of service, and configured to the operation status UNA (e.g. CCG-fault with configuration).

If there is no redundancy the relevant unit is configured to UNA only in the case of strong faults (e.g., LTG-failure may be with/without configuration depending on the severity of the fault).

(d) NAC: A unit whose higher unit is not ready for operation has the operation status NAC, e.g.,If IOPMTD =UNA (defective)status of MTD becomes = NAC (not defective but cannot be accessed).

3. Units which are not present must be in operation status PLA. In this case no tests and therefore no fault messages are produced for these units.

68

• Summary Reference for Status of different units:

Semi-permanent status (Operator controlled)

ACT Active Call processing running and unit is fault free

CBL Conditionally blocked Active for safeguarding, but blocked for call processing

MBL Mtce blocked OOS (Out of service), but acesible for mtce, work

PLA PlannedOOS, possibly without hardware, but foreseen for later extension. Status after creation of a unit.

UNA Unavailable OOS due to fault

Transient Status

NAC Not accessible Higher ranking unit is OOS(Access degradation)

SEZD Seized for diagnostic

SEZ seized by process other than diagnostic

DST Disturbed OOS, but with automatic reactivation

Possible status changes

CONF DLU : DLU= 10, DLUCO = y, OST=new state;

Old statusAllowed Transition

PLA MBL

MBL PLA, CBL, ACT

UNA CBL, MBL, ACT

ACT CBL, MBL

CONF DLUEQ: DLU=10, DCC=x-y, OST= new state;

Old statusAllowed Transition

PLA MBL

MBL PLA, ACT

ACT MBL

69

5.2 Safeguarding FeaturesRoutine Test

Routine tests in the DLU are implemented in such a way as not to disturb or even interrupt call processing operations.

The routine tests controlled by maintenance DLU are implemented in the SW

- of the LTG* and the DLUC.

The following routine tests are performed:

- tsx routine tests to detect defective speech channels

- RAM routine tests of the DLU memory

- DLUC loop test

- RGMG test

- IOP memory test for internal testing of IOP memory areas.

In addition, the DLU emergency service control of the LTG* has some routine test functions.

Emergency Service

Emergency service is begun when the path to the CP is interrupted for both DLU systems (DLUC-O and DLUC-l). During emergency service, telephoning is possible only between subscribers connected to the same DLU.

Audits

Audits are independent monitoring programs for detecting processor internal data inconsistencies. They serve only to confirm the system software functions. (See MMN:SYP, Register FC, Kapitel SYP55).

70

5.3 Fault Printouts

There are four formats for DLU fault printouts. Each format matches one of the following types of printout:

- DLU failure with configuration

- DLU failure without configuration

- RCU link failure -

- External alarm DLU

DLU Failure With Configuration

This type of fault printout is output if the fault is so serious that parts of the DLU receive a state other than ACT.

DLU Failure Without Configuration

This type of fault printout is output for faults which do not cause configuration of the DLU. The DLU retains its current operating state. The format for this fault printout is the same as that for DLU FAILURE WITH CONFIGURATION.

External Alarm DLU

In order to display alarms from external devices, (e.g. air conditioning, entry supervision, power supply) on the SYPD, an ALEX module is included in the DLU. Up to 16 external alarms can be connected to this module via the external DLU alarm lines. One ALEX can he inserted per DLU. The external DLU alarms can also be forwarded to external alarm devices. A specific fault printout can he output by the system for every external DLU alarm.

The commands required for definition, display etc. of these fault printouts is contained in MMN:SYP, register IN, chapter INTRO.

In the same chapter the level definition on the external DLU alarm line is also described. The fault clearance procedures required for the particular fault is to be written by the user. Forms for this purpose are contained in MMN:SYP, register FC, chapter SYP99-DLU.

The MMN number for every external DLU alarm is SYP99-DLU. The alarms are differentiated via the individual alarm message texts. The pin assignments for the ALEX module are contained in Register TAB, chapter LED:DLU.

71

5.4 Fault cleared Messages :

There are two formats for fault cleared messages. Each format matches one of the following printout types:

- DLU fault cleared with configuration

- DLU fault cleared without configuration

- External alarm DLU end

DLU Fault Cleared With Configuration

This format is output after clearing a fault which resulted in configuration to DST.

DLU Fault Cleared Without Configuration

This type of format is output after clearing a fault which did not result in a change of operating state. The format is same as above.

External alarm DLU end

This format is output after an external DLU alarm has been cleared.

5.5 ISDN Maintenance Procedures

No new DLU maintenance procedures are required for ISDN basic access including p-data access to the D-channel-NUCs or B-channel-NUCs. Error detection and the location of faulty modules are provided together with the existing error messages and procedures.

Faults may occur in EWSD exchanges which lead to reconfigurations due to the failure or disconnection of LTG, DIU, PCM highway or Packet Server Module (PSM). If NUCs are taken out of service as a result of such faults, the NUC maintenance software is informed. The maintenance software then informs the operating personnel of the state of the NUCs and ensures that the NUCs are set up again when service is restored. This is standard procedure for conventional NUCs.

The maintenance software defines which error message is output and provides input to the required error procedures.

To comply with essential requirement for channel availability, ISDN P-channel-NUCs (IPNUCs) are supervised end-to-end between SLMD and PSM. The NUCs are supervised using the Maintenance Link Access protocol (M-LAP) by the SLMDs, which poll the PSM every 20 seconds. The PSM responds to each polling request from the SLMD with information on channel availability. The SLMD module is thus the active diagnostic unit for testing ISDN-NUCs. The terminal adapters also contain loopback mechanisms with which the ISDN subscriber service features can be tested. These tests go beyond the scope of MMN:DLU and are described in other documents.

The SLMDs are responsible for collision detection (CD) within the DLU.

72

Maintenance for D-channel access

Failure of a common p-data channel is detected by the SLMDs when the Maintenance Link Access Protocol (M-LAP) fails to respond to polling. Since both common p-data channels are usually used as operating channels for all SLMDs, both channels (X-way and Y-way) are supervised automatically.

End-to-end supervision takes place via M-LAP between the SLMDs and PSM, which check the operating channel at regular intervals (20 seconds) with test messages. If an SLMD detects that its operatng channel has failed, it switches automatically to the standby channel and performs switchover. The SLMD sends the message ‘P-DATA NOT AVAILABLE’ to the DLUC.

After receiving the first SLMD switchover message, the maintenance circuit in the DLUC defines a timer with a delay that is longer than the interval of the administration LAP of the SLMD (30 seconds) and collects all P-DATA NOT AVAILABLE messages from the SLMDs in this period.

When the timer expires, the DLUC attempts to locate the fault and to create an operable configuartion. The DLUC determines whether one, severl or all SLMDs on the operating channel has/have reported the fault. The DLUC reports the fault to the GP, which forwards the signal to the OMT for output.

If a PCM highway is switched off or interrupted, the SLMD is automaticaly informed by the available LTG. The messae P-DATA NOT AVAILABLE is output. The number of the faulty line is also identified. If possible, the SLMD switches to the standby channel.

After switching to the standby channel, the affected SLMDs continue to send messages every 30 seconds to the administration LAP of the faulty operating channel. If one of these messags is acknowledged by the PSM, it can be assumed that the operating channel can be restored to service. A hard switchover is then performed to restore the PCM highway.

The ‘P-CHANNEL AVAILBLE’ message is sent to the DLUC which forwards it to the GP and, in some cases, to the CP for output at the OMT. The SLMD therefore switches automatically back to the operting channel when the PCM highway is restored and reports this to the NUC.

The reasons for switchover as a result of failures in other exchanges can only be identified manually by the operating personnel. However, failures and restorals are recorded automatically as described above and reported to the OMT with the appropriate message.

Maintenance for access on the B-channel

Automatic switchover to standby channels in response to a failure is not a feature of the B-channel NUC. Every NUC is permanently assigned to a specific subscriber and has no redundancy.

The NUC maintenance software is informed of failures of peripheral hardware units that are the consequence of failure or disconnection of LTG, DLU PCM highway, DIU, DLU, module, DLU port or PCM etc.

73

NUC maintenance in the CP informs GP administration, which starts release of the NUC on the system side. In the case of failurs where the CP is unable to determine whether an NUC is affected, NUC administration checks its NUC table to find this out. If an NUC is affectd, a failure message is output at the OMT.

If the DIU with signaling fails all NUCs of this DLU system half are usually released. When the peripheral units of affected NUCs.

DLU Creations :Annexure - I

DLUs are created and configured using MML commands. These commands apply to groups of functional units or to individual modules (Fig 10,11). Data entered during creation generate a memory map of previously unknown functional unit in the Coordination Processor. The functional unit can be placed in the desired operating state (e.g.ACT) by using the corresponding CONF command.

Step 1 : Creation of a new DLU

CR DLU DLU=dlu no…,Shelf =A.

DLUC0 = lsg-itg-diu0 <-diu 1>

DLUC1 = lsg-Itg-diua-2 <diu 3>;

CR DLU MOD: DLU = 20, MOD = 0-2, TYPE = SASC

CR DLU MOD : DLU = 20, MOD = 0-11, TYOE = FMTU

CR DLU MOD: DLU = 20, MOD = 0-12, TYPE = LCMM

CR DLU MOD: DLU = 20, MOD = 0-14, TYPE = EMSP

CR DLU MOD : DLU = 20, MOD = 0-15, TYPE = ALEX

CR DLU MOD: DLU = 20, MOD = 1-11, TYPE = EMSP

CR DLU MOD: DLU = 20, MOD = 0-6, TYPE = SLMACOS

CR DLU MOD: DLU = 20, MOD = 0-1 TYPE = SLMACMRL

74

Step 2 : Configuration of all equipment to MBL

Conf DLU : DLU = 20, DLUC0=yes, OST = MBL;

Conf DLU : DLU = 20, DLUC1=yes, OST = MBL;

Conf DLUEQ : DLU = 20, RGMG =0, OST = MBL;

Conf DLUEQ : DLU = 20, RGMG=1, OST = MBL;

Conf DLUEQ : DLU = 20, DCC=0-0, OST = MBL;

Conf DLUEQ : DLU = 20, DCC=0-1, OST = MBL;

Conf DLUEQ : DLU = 20, DCC=1-0, OST = MBL;

Conf DLUEQ : DLU = 20, DCC=1-1, OST = MBL;

Conf DLUEQ : DLU = 20, DCC=2-0, OST = MBL;

Conf DLUEQ : DLU = 20, DCC=2-1, OST = MBL;

Conf DLUMOD : DLU = 20, Mod=0-2, OST = MBL;Repeat for all modules created at ‘A;

Conf DLU PORT : DLU = 20, LC=0-6-0 & OST = MBL0-6-7,

Configure all the ports similarly

Caution : Don’t forget to configure the TU ports as well.

Step 3: Configuration to ACT.

Repeat all the above steps to bring the DLU, DLUEQ, DLUMODs and the DLUPORTs to ACT;

75

Annexure - II

1.0 Call Setup Under Normal Operation

Prerequisite for normal operation of a DLU is that it can communicate with at least one LTG via a PDC with CCS. In order to achieve a very high level of reliability for the DLU and its connection with the LTGs, the following measure have been taken :

- duplication of the DLU systems (DLUC, DIUD and CG)

- two or four primary digital carriers (PDC)

- connection to two LTGs

- the use of one common channel signalling (CCS) link per LTG.

Under normal operating conditions, a DIUD automatically forwards the information octets from a specific subscriber terminal to a PDC channel. The same principle applies in the opposite direction of transmission. Under normal operating conditions, a fixed allocation exists between the 4096 kbit/s network channels and the PDC channels via the DIUD (see also Fig.3) which means that the DIUDs do not have to perform any additional switching functions. At the same time, a DLU control (DLUC) only handles communication between the SLMCP in the DLU and the group processor (GP) of the associated LTG.

In the following description of a connection setup, the functional units assigned to the calling party are designated A-…. (e.g. A-LTG, A-DLUC) and the functional units assigned to the called party are designated B-….(e.g. B-LTG, B-DLUC).

1.1 Outgoing connection

If an outgoing connection is to be set up (e.g. calling subscriber goes off-hook), the A-SLCA recognizes this change of state and informs the A-SLMCP. A corresponding report is sent to the first A-DLUC which interrogates (polls) the A-SLMCP. This A-DLUC is now responsbile for the setup and later release of this outgoing connection. The A-DLUC forwards the report via the common channel to the associated group processor (GP) in the A-LTG. The A-GP

- determines the calling party’s class (e.g. subscriber with rotary dialing)

- specifies the time slot (channel) to be used in the A-DLU and forwards. This via the common channel to the A-DLUC.

- Informs the CP of the seizure and

- Through-connects the group switch (GS) in the A-DLU

76

The A-DLUC forwards the specified time slot to the A-SLMCP via the control network, the A-SLMCP loads the A-SLCA with this time slot.

The A-GP causes a loop check to be carried out from the A-LTG (A-LTG – A-DIUD – ASLCA – A-DIUD – A-LTG). After a successful loop check.

- The A-GP sends a through-connect command via common channel and A-DLUC to the A-SLMCP

- Causes the dial tone to be applied from the A-LTG via one PDC channel, the A-DIUD and the 4096 kbit/s network in the relevant time slot to the A-SLCA

On receipt of the through-connect command the A-SLMCP forwards the dial tone from the A-SLCA to the calling party.

The A-SLMCP integrates the incoming dial pulses (conversion to digital information) and forwards this information via control network, A-DLUC and common channel to the A-GP. The A-GP disconnects the dial tone after the first digit has been received the complete dialed number is sent via the switching network (SN) to the CP.

If the A-GP indentifies the subscriber’s class as subscriber with push-button dialing, it causes a push-button receiver in the A-LTG to be connected. In this case the calling party’s dialed information is forwarded via the A-SLCA, 4096 kbit/s network in the relevant time slot, A-DIUD and a PDC channel to the push-button receiver in the A-LTG.

1.2 Incoming connection

The CP receives the complete directory number of the called party from the A-GP. It determines one of the two B-LTGs, to which the B-DLU is connected and links this LTG via the switching network with the A-LTG. The B-GP of the B-LTG assigns the time slot to be used in the B-DLU and transmits a seize command and this time slot via the common channel, B-DLUC and the control network to the B-SLMCP. The B-SLMCP load the B-SLCA with the specified time slot.

After a successful loop check from the B-LTG (B-LTG – B-DIUD – B-SLCA – B-DIUD – B-LTG) the B-GP sends a ring command via the common channel to the B-DLUC. The B-GP also causes ringing tone to be applied from the B-LTG via the switching network and the A-LTG to the calling party. The B-DLUC causes the calld party to receive ringing voltage and control splash ring and periodic ringing via the B-SLMCP.

When the called party accepts an incoming call by going off-hook (loop closure), the ringing current and ringing tone are disconnected. The B-DLUC sends an appropriate report via common channel to the B-GP and this is also forwarded to the A-GP of the A-LTG. The B-GP causes the group switching to through-connect to the switching network. The connection is then established.

77

2.0 Call Setup Under Emergency Service

Prerequisite for initiation of emergency service in a DLU is that the DLU is no longer able to communicate with a minimum of one LTG via a PDC with CCS, e.g. total breakdown of the connections to the LTGs. In this cse, the DLU switches over to continue operation in emergency service. Emergency service is not provided for local DLU connection to LTGFs.

Emergency service provides the subscribers connected to the same DLU with facilities for setting up connections to one another (DLU internal traffic). Up to 60 simultaneous connections can exist. No charges are registered during emergency service.

To enable control of connection setup during emergency service, it is necessary for the DLUCs to contain all the latest, up-to-date subscriber data. For this purpose, the DLUCs constantly receive during normal operation the relevant, changed or additional subscriber data from the LTGs.

Under emergency service conditions, however, the DIUDs do not through-connect the information octets of the 4096 kbits/ networks to the PDC channels, but loop them back to the SLCAs. The DLUCs are responsible for routing the octets in the channel originating from the calling subscribers to the SLCA of the called subscribers and vice versa.

During emergency service, the DIUDs also supply the dial, ringback, ringing and busy tones. If a DLUC detects that the directory number of a subscriber that is not connected to the DLU has been dialed, it tells a DIUD to send a busy tone to the calling subscriber.

Under normal operating conditions, dialed information from a push-button subscriber is received and evaluated by an LTG. For emergency service, push-button receivers are provided in the EMSP functional units in the DLU and these are connected if required.

2.1 Internal connection

If a connection is to be set up (e.g. calling subscriber goes off-hook), the associated A-SLCA recognizes this change of state and informs the A-SLMCP. A corresponding report is sent to the first DLUC which interrogates (polls) the A-SLMCP. This DLUC is now responsible for the setup and later release of this internal connection.

The DLUC

- Seizes a free push-button receiver in an EMSP and

- Forwards the fixed time slot for dial tone to the A-SLMCP.

The A-SLMCP loads this time slot into the A-SLCA.

The DLUC sends a through-connect command to the A-SLMCP

The A-SLMCP causes the calling party to receive dial tone from the DIUD via the 4096 kbit/s network.

78

(a) Calling party with rotary dialing

The A-SLMCP integrates the dial pulses (converts them into digital information) and passes this information on to the DLUCs via the control network.

(b) Calling party with push-button dialing

The A-SLCA forwards the dialed digits via the 4096 kbit/s network and the DIUD to the push-button receiver in an EMSP. The push-button receiver converts the dialed digits into digital form and passes them on to the DLUCs via the control network.As soon as the first dialed information in received, the DLUC

- Sends a command to the A-SLMCP to disconnect the dial tone and

- Determines the time slot for the speech connection.

The A-SLMCP disconnects the dial tone in the A-SLCA.

As soon as the DLUC has received all digits it releases the EMSP (if a subcriber has push-bialing) and sends the fixed time slot for ringing tone to the A-SLMCP. The A-SLMCP loads this time slot into the A-SLCA and the calling party receivers ringing tone from the DIUD via the 4096 kbit/s network.

The DLUC sends a seize command to the B-SLMCP.The B-SLCA is loaded with the time slot for the speech connection and the subscriber loop is switched to low resistance.

The called party receives ringing current.

The B-SLMCP controls the ringing current.

When the called party accepts an incoming call by going off-hook (loop closure), the ringing current is disconnected.

The B-SLMCP- through-connects the B-SLCA to the 4096 kbit/s network (specific time slot for speech connection)

- sends an appropriate report to the DLUCThe DLUC forwards the time slot for the speech connection to the A-SLMCP.

The A-SLMCP

- loads the time slot for the speech connction into the A-SLCA

- thereby disconnects the ringing tone.The connection is now established.

79

6.0 Exercises (DLU-Finctional Structure and Maintenance)

Exercise 1

Write down all MML-commands to get a printout of the operational status of the following units:

1. PCM-link

2. DLU-controller

3. DIUD

4. RGMG

5. BDB

6. BDCG

7. BDE

8. DCC

9. TU

10. EMSP

11. Subscriber modules

12. Subscriber Line Circuits.

Exercise 2

A new module SLMA for ordinary subscriber has to be added in DLU10, Shelf 2, 1st module location. Write down all necessary MMLcommands.

Exercise 3

The controller for Stand-Alone-Service (SASC) is to be inserted in DLU 20. Write down all necessary MML commands to create and to display the SASC.

Exercise – 4

A new module frame for Subscriber Line Modules is mounted.Write down all MMl commands necessary to prepare the new frame.

80

Exercise 5

Complete the following tableSituaion LED Indication of LED

(On, Off, Flashing)No access degrading (Normal operation)DLUC 0 G1

G2DLUC 1 G1

G2

Emergency serviceDLUC 0 G1

G2DLUC 1 G1

G2

BDCGOMaster functions M

Exercise 6

Specify the changes of the operational status and access degarding inside the DLU in the case of a failure of PCM-link side 0 (with CCS).

Exercise 7

Create an RCU consisting of 2 R-DLUs (DLU-20 and DLU-30). Can you check the stand-alone cluster operation when DLU-20 is cut-off from the main switch?

81

LINE/TRUNK GROUP

What is inside ?

1. Introduction2. Connections

2.1 Subscriber Connection

2.2 Message Channel connection

3. Functional Unit in LTG

3.1 Line/Trunk Unit

3.2 Signaling Unit

3.3 Group Switch and Interface Unit

3.4 Group Processor

4. Group Processor Software

5. Physical Design

6. O & M Aspects

Abbreviations

Exercises

82

Line / Trunk Group

1.0 Introduction

The line/trunk group (LTG) is a subsystem of EWSD. The LTG forms the interface between the digital environment of an EWSD exchange (FIG. 1.1) and the switching network (SN).

Figure 1.1 : Functional Units of EWSD

1.1 Configuration Options:

Different possible configurations for an LTG are as follows :With digital transmission link (primary digital carrier, PDC)

- For digital line unit (DLU) operating at transfer rate of 2048 kbit/s. DLUs can be used to connect analog as well as digital subscribers (e.g. with PDC at 2048 kbit/s; ISDN basic access BA for ISDN subscribes and small ISDN PBXs). When connected via PDC, the DLU is generally operated as a remote unit with respect to the EWSD exchange.

- For digital trunks with transfer rate of 2048 kbit/s.With digital transmission link for local operation of DLUs (i.e, DLUs within the main exchange) at transfer rates of 4096 kbit/s

83

With primary rate access (PA):

For medium-size and large ISDN PBXs (ISDN subscribers with PA) opeating at transfer rte of 2048 kbit/s.

1.2 LTG types:

Different hardware versions of LTGs exist for the various configurations above. This document deals only with line/trunk groups of type G, i.e. LTGG:

LTGG (B-function) for DLU and PA

It is possible to connect combinations of DLU and PA to the same LTGG. The transfer rate is 2048 kbit/s.

It is also possible to connect trunks (with or without multifrequency code MFC), provided they have the same transfer rates as DLU/PA. DLUs can be operated as local or remote. Local operation can be converted to remote operation.

• LTGG (C-Function)

Exclusively for trunks with / without MFC. The transfer rates are 2048 kbit/Sec.

1.3 The transfer rate on the secondary digital carrier (SDC) from the LTG to the SN and viceversa is 8192 kbit/s ( 8 Mbps). Each of these SDCs has 128 time slots

of 64 kbit/s each, out of which 127 time-slots are used for user information and one time slot for messages. User information is the information relevant to the communication partners (voice, text, data, images). Messages are used’ for interprocessor communication in the EWSD system, e.g., in the case of the LTG, for communication with (a) the coordination processor, (b) other LTGs and (c) the CCNC. User information and messages are transferred together.

Line/trunk groups can operate with all conventional signaling systems and can therefore be easily integrated into any switching system. Signaling is the communication between exchanges. Analog user information and analog signals are digitized by means of a signal converter, multiplexer (SC/MUX) outside the EWSD exchange.

84

1.4 LTG Functions

The main functions of the LTG are

(a) Call processing functions include

— Receiving and evaluating signals from the trunk and the subscriber line

— Sending signals

— Sending audible tones

— Sending messages to the CP and receiving commands from the CP

— Sending/receiving reports to/from the group processors (GP)

— Sending/ receiving orders to/from CCNC

— Controlling the signals to DLU, PA

— Adapting the line conditions to the 8 Mbps standard interface to the SN

— Through-conncetion of messages and user information

(b) Safeguarding functions include

—Detecting errors in the LTG (without external test equipment)

—Detecting errors on the connection paths within the exchange viacross-office checks and bit error ratio counting (BERC)

- Transferring error messages to the CP

- Evaluating errors to determine penetration range

- Initiating measures corresponding to the penetration range of an error(e.g., blocking of individual channels or blocking of entire functionalunits of the LTG).

- Exchanging routine test messages with the CP, so that the CP can detecta faulty LTG if the LTG itself is not able to send error messages.

(c) Administrative functions include

- Sending messages to the CP for traffic measurements and trafficobservation

85

- Switching of test connections

- Testing of trunks and port-specific areas of the LTG using the automatictest equipment for trunks (ATE:T) integrated in EWSD and theautomatic test equipment for transmission measuring (ATE:TM).

—Indicating important information(e.g. channel assignments) to the functional units

—Creating, blocking. releasing devices via MML commands.

2.0 Connections

As indicated under Sec. 1.2, two types of connections exist for the LTG time-slots

(a) Subscriber connections

(b) Message connections

2.1 Subscriber Connections

A subscriber connection is a connection that carries user information. Subscribers may include ordinary telephone subscribers as well as telecopiers and facsimile equipment. To set up subscriber connections, each LTG has 127 time slots (1-127), also called channels, per 8-Mbit/s multiplex system. 120 time slots are used for transmission. Subscriber connections are through-connected by the SN. Each subscriber connection occupies one time slot in the forward direction and one time slot in the backward direction; the two time slots are identical within their multiplex system (Fig 2.1). The calling subscriber A is assigned time slot x, for example, by the Group Processor. GP. This GP is located in the LTG of the A-side (in Fig. 2.1: LTG1)

The called subscriber B is assigned time slot y, for example, by the CP. The SN combines time slots x and y in a time slot z.

The two switching networks (SNO and SN1) work in hot standby mode. An LTG always sends and receives the user information on the SDC through both SN-halves (SNO and SN1). Thus, both SN-halves contain the same user information. However, an LTG assigns only the user information from the active SN-half to the respective subscriber (A- or B-side). The other SN-half is designated as standby and, in the event of a failure, is able to take over immediately and send and receive the up-to-date user information. To do this, it must be configured from standby to active. The link interface unit (LIU) between the LTG and SN, located in the LTG, then receives information from the other SN-half

86

Figure – 2.1 : Subscriber Connection (SN0 active)

2.2 Connections of Message-channels

The GP of an LTG exchanges messages (interprocessor communication with)

(a) the GP of other LTGs in the same exchange,

(b) with the CCNC, and

87

(c) with the CP.

To do this, each LTG uses time slot 0 of each SDC to and from the SN. This connection is called the message channel (MCH). The message channel is implemented as a semipermanent connection which is set up when the system is placed in service or restarted and then remains connected. Like subscriber connections, message channels are always through-connected to the 2 Message Buffers simultaneously through the respective SN-half. The GP or the message buffer for the CP, however, uses only the messages from the active MCH; the other MCH is designated as standby. Since the MB-O and MB-1 work on load-sharing basis (i.e. GPs of half LTGs communicate with the CP via MB-O; the other half LTGs being handled by MB-1), the standard distribution of the ACTIVE message channel of LTGs to the MBs is as below:

LTG Active MCH LTG Active MCHNo. via no. via

12 SN-11 SN-1 13 SN-02 SN-0 14 SN-13 SN-1 15 SN-04 SN-1 - -

SN-1SN-0

5 SN-06 SN-0 60 SN-17 SN-1 61 SN-08 SN-1 62 SN-19 SN-1 63 SN-0

In the event of failure of an active message channel, the CP initiates the configuration of the message channel in the other SN-half to active.

Table 2.1 : Standard distribution of ACTIVE message channels of LTGs in SN—halves 0 and 1

Table 2.1 shows the SN-half in which the active MCHs for each LTG are located. The MCHs are monitored by the LTG as well as by the MB. Thus, the hardware of the SN is monitored at the same time, since the MCHs are integrated in the SN hardware. Message distributor 0 (MBO) is assigned to SNO, message distributor 1 (MB1) to SN 1. The method used in transferring messages on the MCH is an HDLC procedure.

The exchange of messages is illustrated in Fig 2.2.

88

1. Messages from the GP:

The messages originating in the GP [messages to the CP, reports to the GP and orders to the [CCNC; (see Sect. 4)] are transmitted in time slot 0 on the MCH through the SN and to the MB. All LTGs are connected to the SN in parallel (Fig 2.3). By design. each LTG (is assigned to a specific SN-half for message distribution ( table 2. lists the standard assignments). Fig. 2.2 shows an example of a Configuration with 63 LTGs (1-63), using LTG-1 and LTG-63 to illustrate how messages are transmitted.

The GP of LTG 1 sends a message through the LIU to SN 1. In the process, the LIU inserts the message in time slot 0 to the SN. SN1 forwards the message in time slot x. On the MCH from the SN to the MB, SN1 transfers the messages of all LTGs serially to the MB The SN transfers the message from LTG 1 in time slot 2.

An analogous procedure is used fur a message that is to be simultaneotislv transferred from LTG63 to the CP. The difference is that LTG63 is assigned to SNO a different time slot (y) is used within SNO, and a different time slot (126) is also used to transfer the message to the MB. Consequently MBO receives the message from LTG63, MB1 receives the message from LTG1. The MB buffers this data until it is received by the input/output processors (IOP) in the CP. The corresponding IOP determines whetheer the data involves a message for the CP or a report for a GP and, accordingly, stores the messages in the input list and the reports in the output list of the CP.

If one the units on time message transmission path becomes faulty (e.g. SN-half or MB, fault detection mechanisms configure the defective unit from active to unavailable. The unit that was previously standby then takes over the functions of the faulty unit. Assuming that SN 1 was configured to unavailable, SNO takes over all those LTGs. Which are normally assigned to SN1 (LTG1, LTG3, LTG4, LTG6, etc; See Table 2.1). The GP of LTGI then sends the message to SN 0. To do this it uses he MCH represented by the broken line in LTG 1 in Fig. 2.2 as the active MCH. SNO forwards the message in time slot x (the time slot is the same in both SN-halves). On the message channel from SNO to the MB, this message is assigned to time slot 2. The lOP in the CP no longer polls MB 1 as usual, but rather MBO, from which it obtains the messages from LTG1 (as well as from the other LTGs which previously transmitted via SN 1).

89

Figure 2.2 : Exchange of Messages between LTG and CP, LTG and LTG (SN with 63 LTGs)

90

Figure – 2.3 : Assignment of message Channels (time slots from LTG to MB

2. Messages to the GP

Data being sent to a GP (e.g. commands from the C P or reports from other GPs) are read by they; IOP from the CP memory unit. The IOP forwards the data to the MB associated with the respective LTG (e.g., MB I for LTG 1). The MB buffers the data and assigns the data to the assigned time slot towards SN. For LTG-l, this is time slot 2. SN I transfers the message in time slot x and forwards it to LTG-1 in time slot 0 (the time slots in the SN are the same for the forward and backward directions, as are the time slots on the MCH). The other LTGs receive their messages in the same manner. The LIU extracts the messages from the information received from the SN (user information and messages) and forwards the messages to the GP. The above description applies analogously for LTG63 (and other LTGs), as well as for reconfigurations in the event of faults.

91

3.0 Functional Units

The line/trunk group LTGG is made up of the following functional units:

• Functional units in the line/trunk unit (LTU)

• Functional units in the signaling unit (SU)

• Group switch and interface unit (GSL)

• Group processor (GP)

Fig 3.1 shows the LTGG and its functional units and main interfaces. The subsections that follow describe the individual functional units and their interfaces. The figures associated with the descriptions show the interfaces that are essential for the respective functional unit.

Table 3.1 and 3.2 provide an overview of the speech and signal highways of an LTG. Speech highways (SPH) transfer user information, signal highways (SIH) transfer messages.

Table – 3.2 : LTGG : Speech highway (SPH) for user information

Table 3.2 : LTGG : Signal highway (SPH) for messages.

92

Figure – 3.1 : Functional Units of LTGG

93

3.1 Line/Trunk Unit

The line/trunk unit (LTU) is a logical unit which can have a number of different functional units (Fig 3.2). The purpose of these functional units is to adapt connected lines to the internal interfaces of the LTG and to equalize signal delays (synchronization of exchange bit rate and line bit rate). They also process the signals to and from the connected lines.

By means of the signal highway output (SIHO), the LTU receives commands from the GP (e.g. exchange codes to be transmitted); by means of the signal highway input (SIHI), the LTU sends peripheral-event information to the GP. Address signals (from the GP to the LTU and SU) control the SPH and SIH used to link the LTU with the GSL and GP.

The functional units listed below can be plugged into the LTU.1.(a)Digital Interface Unit (DIU)

Digital interface unit (DIU) is used for connection of remote DLU, PA, digital trunk [ up to four digital interface units (DIU30, i.e 2 Mbps) per LTGG]; and for connection of external test equipment, such as the automatic transmission measuring and signaling testing equipment (ATME) and the trunk test equipment answer unit (TTE/AU). The signaling methods used are channel associated signaling (CAS) and common channel signaling (CCS).

In EWSD, an (external) digital announcement system (DAS) is connected to a DIU on a single PDC. With the DAS, the operating company can store variable or permannent announcements and output them on a channel specific basis. A DAS is connected via a 2 Mbps transmission link. The DAS consists of a base unit with speech memory cards for annoucements. The number of announcements can be increased through the use of an expansion unit containing additional speech memory cards. Creation of database for announcement lines will be discussed under ‘Routing Administration’.

(b) Local DLU interface, modul B (DIU : LDIB)

Local DLU interface, module B (DIU : LDIB) is used for connection of local DLU. In the most common application, each LTGG has two DIU : LDIB each DIU:LDIB having 60 channels on the 4096 Kbit/s transmission link to the DLU. Other configurations, e.g. combinations of local and remote DLUs connected to the same LTGG, are possible. A DIU : LDIB replaces two 2048 kbit/s transmissionlinks with a 4096 kbit/s transmission link. The DIU : LDIB of the LTGG communicates with the functional unitDIU:LDID in the DLU. The signaling method used is common channel signaling (CCS)

94

Figure – 3.2 : Functional units of the line/truk unit (LTU)

2. Conference unit, module B (COUB)

The conferencing unit occupies the slot reserved for LTUs and hence, is configured as an LTU. A single COUB module contains four individual conference units. Each of the conference units can connect up to 8 channels (e.g. 8 subscribers). It is also possible to cascade two conference units, so that as many as 14 channels can be connected.

95

3. Code receiver (CR)

The following type of Code receivers can be used in the LTU if the capacity for CR in the SU has been exceeded:

- Multifrequency code receivers (CRM)

- Code receivers for push-button (DTMF) dialing (CRP)

Code receivers are implemented as a digital signal processing module, extended (SPME). The SPME is programmed for the functions of CRP or CRM (and module RM:CTC in the SU) yia the firmware . An SPME can accommodate 8 CRs.

4. Automatic test equipment (ATE)

The ATE is used in one of two variants.

The automatic test equipment for trunks (ATE:T) is used for routine testing of trunks and tone generators (TOG). The ATE:T consists of the test equipment module for level transmitting and measuring (TEM:LE).

The responder used with ATE:T can be, for example, the EWSD system-integrated end-to-end test equipment, answer equipment (module) (ETEAE), another responder (e.g. implemented with TEM:LE), or an automatic subscriber.

The automatic test equipment for transmission measuring (ATE:TM) is the equipment used for manual demand testing of trunks with the trunk work stations (TWS) and serves as director or responder within the ATME2 when testing international trunks. The ATME2 is specified by CCITT. The ATE:TM consists of the module ATE:TM.The modules of ATE, like the ETEAE, are plugged into the LTU of LTG..

5. The operationally controlled equipment for announcement (OCANEQ)

For an individual digital announcement system (INDAS), it can be plugged into slots of the LTU.

Using INDAS, the operating company can assemble announcements from permanently stored announcement fragments. The announcement fragment is stored in the memory unit of OCANEQ. An announcement can be an individual (i.e. customized) announcement or a general-purpose, standard announcement. An example of an individual announcement would be a message regarding the setting of an alarm ca11, a standard announcement might be a message indicating that a directory number has been changed.

96

INDAS consists of OCANEQ which is plugged into the LTG, and the CP software and GP software. In its basic configuration, OCANEQ contains a module M:OCE:SPC and a module M:OCE:MUP. One module is inserted for each LTU. Expansion is possible in increments of one module each, up to a niaximum of four modules.

3.2 Signaling Unit

The signaling unit (SU) is a logical unit that can accommodate various functional units (Fig 3.3). In the LTGG, these fuiictional units may be: TOG, CR, RM:CTC.

(a) Tone generator (TOG)

The TOG centrally generates the audible tones required for all LTUs as well as the frequencies for testing the code receiver. These frequencies are stored as bit patterns in a replaceable memory chip. Bit patterns are converted into analog form in the functional unit requiring them.

(b) Code receiver (CR)

Depending on the type of LTG, the SU contains code receivers for pushbutton dialing i.e. DTMF dialing (CRP) and/or for multifrequency code receivers (CRM) for trunks with channel associated signaling (CAS). The CRP or CRM is assigned to DTMF subscriber line or MFC trunks only for the duration of the digit input.

(c) Receiver module for continuity check (RM:CTC)

When trunks with common channel signaling (CCS#7) arc used, the recciver module for continuity check (RM:CTC) is required.

After a connection is set up, an RM:CTC can he assigned to the incoming line. A signal transmitted by the TOG on the outgoing line and looped back at the destination is detected and analyzed. It is recognized whether the call setup has been successful and whether line attenuation is too high for satisfactory transmission quality. If the attenuation is too high, the connection is released, and a new connection is set up.

The SU is connected to the GSL via SPHO/I and to the GP via SIHO/l . The SU receives commands from the GP via SIHO and sends signaling characters to the GP via SIHI. SPHO/I and SIHO/I are controlled by address signals (from the GP to SU).

97

In the case of MFC signaling; the inband signals from the DIU are forwarded to the GSL via SPHI. From there, the signals are fed to the CRM via SPHO. The CRM evaluaies the signals and sends the iesults of the evaluation to the GP.

Figure - 3.3 : Functional units in the signaling units (SU)

98

3.3 Group Switch and Link Interface Unit (GSL)

The functional unit “Group switch and interface unit (GSL) is made up of

- a group switch (GS) part and

- a link interface unit (LIU) between LTG and SN.

These two parts communicate with one another.

1. The GS part of the GSL represents a non-blocking time stage controlled by the GP. The GS part through-connects user information that was received from the SN or from the functional units in LTU/SU. User information can be attenuated on a channel specific basis as needed. Double-connection checks can be performed.

Twelve speech highway, output/input units (SPHO/I- 0.... 11) connect the GS part to the GP, LTU and SU.

SPHO/I-11 transfers test information between the GS part and the GP; the GSL extracts SPIH-1l from CDIM; it injects SPHO- 11 into CDAM. CDAM (Control data Acknowledgment Message) and CDIM (Control data Input Message) are used for exchanging messages between GP and GSL. Within the GSL, both lines support the GS part as well as the LIU part. The GSL receives setting conimands from the GP via CDIM and stores them in its input memory. The GSL interprets the command, issues the necessary settings for the hold memory, and writes the acknowledgment in its output memory. The GSL transfers the acknowledgment to the GP on CDAM.

The GS part operates with up to 5 LTUs (0 .. 4) and the SU. Each speech highway, output (SPH0) and speech highway, input (SPHI) has 32 channels, each of which operates at a data rate of 64 kbit/s. The total bit rate on each SPHO/1-0... 11 is therefore 32x64 kbit/s = 2048 khit/s, or 2 Mbit/s.

The TOG in the SU sends data to the GS part on SPHI-0 and SPHI-1; the CRs in the SU receive data on SPHO-1 (LTGG with C-function) or SPHO-0 (B-function; see also Figs 5.2 and 5.3).

In the case of LTGG with B-function, LTU4 (with SPHO/1-6) replaces a logical unit SU (with SPHO-1).

2. The LIU part of the GSL connects the SN to the LTG. The DATO lines lead to the duplicated SN (DATO-0 to SNO, DATO- 1 to SN1), whereas the DATI lines emanate from the SN (DAT1—0 from

99

SNO; DAT1- 1 from SN1). The data stream on DATO and DATI consists of user information and messages. The multiplexer in the LIU part through-connects the user information from the active SN part (SNO or SN1 ) to the GS part on a channel-specific basis. The GS part is controlled by the LIU part. The GP (i.e. the SM X part of the CGSM ) indicates to the LIU part the appropriate settings for the multiplexer. The process is analogous in the opposite direction (from the GS part to the SN).

The LIU part extracts the CP commands intended for the GP arriving in time slot 0 from SNO or SN1, and sends them to the CGSM of the GP on MCHO.

Figure – 3.4 : Functional Unit ‘Group Switch and interface unit (GSL)’ for LTGG

100

In the reverse direction, messages which are intended for the CP and which arrive from the CGSM on MCHI are injected by the LIU part into time slot 0 of the data stream to the SN. Lines MCHI and MCHO are redundant (MCHI-0, MCHI-I and MCHO-0, MCHO-I). In the event of a failure on the transmission path for messages (see Sect. 2.2), the standby line takes over the functions of the faulty line.

After the call has been through-connected, the LIU part performs a cross-office check (COC) through the SN-halves. The purpose of the COC is to detect and, if possible, localize faults. In the COC, a test bit pattern from the LIU part of the LTG of the calling subscriber is sent to the LTG of the called subscriber, where it is looped back and returned to the sending LIU part. The LTG at this end compares the transmitted and received bit patterns and, if they match, confirm that the existing conncetion will be used for transferring information. If the bit patterms do not match (error condition), the LTG releases the connection and initiates a second, independent call attampt. If the second attempt also fails, the connection setup request from the calling subscriber is rejected.

Group Processor

The functional unit group processor (GP) is an independent control unit. The GP controls the functional units of the LTG and comprises the following individual modules (Fig. 3.5).

1. Clock generator and signal multiplexer (CGSM)

2. Processor memory unit (PMU)

3. Signaling link control (SILCB), when DLU/PA are connected to LTG

1. CGSM Module (Clock Generator and Signal Multiplexer)

The clock generator and signal mjltiplexer (CGSM) in the GP is made up of three parts :

- the clock generator part (CG part),

- the message channel part (MCH part), and

- the signal multiplexer part (SM part).

The CG part receives the clock pulses supplied from both SN-halves via the GSL (LIU part). Using the supplied frame mark bit (FMB), the CG part synchronizes the LTG clock with the SN clock. To do this, the GSL derives the synchronization pulses SYNI from the FMB on an SN-specific basis (SYN1-0 for SN0, SYNI-l for SN1). The CG part selects one of the two synchronization pulses SYNI and synchronizes the LTG clock to this pulse.

101

The synchronization pulses SYNI are monitored by the CG part. An alarm is generated if more than one period of this synchronization pulse is lost. Synchronization of the LTG clock with SYNI is also monitored. The CG part sends alarm data to the signal buffer of the PMU. Alarm data includes

- Alarm in the event of synchronization failure

- Alarms for LTG clocks with reference to transfer rates of 2048 kbit/s

- Indication of which synchronization pulse is currently being used.

It is also possible to transmit loop-back bits for test purposes. From the signal buffer of the PMU, the CG part also receives the control data for

- Selection of synchronization pulse SYNI-0 or SYNI-1

- Alarm test/alarm reset with reference to transfer rates of 2048.

- Setting loop-back bits for test purposes

All other clock pulses and synchronization signals required for the LTGG are generated internally by the CG part of the GP. It is also the task of the CG part to monitor the PMU and, in the event of a supply voltage failure, to reset the PMU.

The MCH part sends and receives messages to and from the GSL on the MCH. MCHI goes to the LIU part of the GSL: MCHO comes from the LIU part of the GSL.

The SMX part receives the serial signaling data on SIBO from the signal buffer of the PMU. It distributes and transmits these data to the LTUs and the SU on SIHO and adjusts the timing accordingly.

The serial data arriving from the LTUs, the SU, the GS and the LIU are received by the SMX part on SIHl; the SM X part adjusts the timing and sends the combined data to the signal buffer of the PMU on a 2048 Kbit/s highway (SIBI). The data can also be filtered, if necessary. The signal buffer forwards the data to the PMU, where they are processed with the help of the GP software and (if applicable) buffered.

The SMX part controls the LTUs and SU with address signals and has a loop-back function for SMX testing. It receives control data for the loop-back function from the signal buffer of the PMU. The interface to SU/LTU is represented by the inputs SIHIM-017, SIHI- 2...5, SIHIM- 1112 and the outputs SIHO-0, 1

102

Figure – 3.5 : Functional Unit “Group processor (GP)”

103

2. PMU Module (Processor Memory Unit )

One single module, the PMU replaces the functions of the PU:SIB and MU modules.

The Processor Unit (PU) which uses a 32-bit microprocessor takes over data processing in the LTG. The memory unit (MU) is available to the PU as program and data memory. The BOOTS bootstrap program. which is stored in the PU’s EPROM, control the loading of programs into the MU.

The PU takes over (parallel) preprocessed information from the Signal Buffer (SIB) for further processing and transmits (parallel) processed information to the SIB, which then passes it on to the SMX in serial format.

During system start, the CP loads the programs and data of the LTG software into the Memory Unit (MU). The storage medium is organized by word (32 valid bits and 7 correction bits a corrcction component detects and corrects 1 -bit errors and detects 2—bit errors. Programmable write protection protects predefined storage areas against accidental overwriting. The memory capacity can be 4 Mbyte or & Mbyte.

Status indicators on the faceplate show which functions are active during loading and operation.The Signal Buffer (SIB) has an interface to the SMX via the 2048 kbit/s multiplex connection (SIBO/l) and an 8-bit parallel interface to the PU. The SIB takes over the serial—parallel and parallel-serial conversion during data transmission between the SMX and the PU buffering the information to be transmitted. It only buffers information that has changed since the last transmission (last look), thus relieving the PU.

3. SI LCB Module (Signaling Link Control)

(Required only in LTGG – B function)

In the case of an LTGG with DLU/PA connected to it, the GP contains an additional functional unit, viz SI LCB. The SILCB handles the exchange of messages with DLU/PA and also controls the CCS channels. The GSL extracts the messages and sends them to the SILCB via SPHO-10. The SILCB edits the messages and adapts them to the transfer rate of the GP. In the opposite direction, the SILCB sends messages to the GSL via SPHI-10 and the GSL injects the messages. Four SILC functional units are provided by SILCB.

104

4.0 Group Processor Software

The GP software controls the functional units of the LTG. It monitors the timing of sequences in the LTG and processes events from the LTG and from the LTG periphery. To properly perform their call processing, administrative safeguarding tasks, the LTGs are in constant communication with the CP (interprocessor communication). The following types of messages are exchanged:

• The CP, being higher in the processor hierarchy, sends commands to the GP.

• Conversely, the GP sends messages to the CP

• A GP exchanges reports with other GPs,

• With the common channel signaling network control (CCNC), the GP uses orders.

Table 4.1 summarizes the various forms of interprocessor communication and the processors involved in each case.

DLU GPGP CP MessageGP DLUCP GP CommandGP GP ReportCCNC (if used) GP Order

4.1 Interprocessor communication in EWSD

The GP software performs the following tasks:

* Interproccssor communication

* Control funtional units of the LTG, particularly switching of LTG-internal time stages GSL.

* Administration of timers Metering of charge pulses Ensuring availability (configuration, starting recovery, checking validity, alarm

Handling, routine tests and audits). Administration of zone tables, traffic measurement, etc. (administrative tasks) Administration of transient and semipermanent data.

105

The GP software is distributed aniong the folloiving functional units :

1. LTG call processing

2. LTG safeguarding

3. LTG Administration

4. LTG operation

5. LTG utilities

6. LTG PCM carrier processing

7. LTG test and measurement

The location of’the software functional units within the system is shown in Fig 4. 1.

Figure – 4.1 : Location of software functional units in the system

106

4.1 LTG Call Processing software module

The functional unit “LTG call processing” contains general routines and call processing user programs.

General routines

A general routine implements functions which are used by several User programs, e.g. data accea routines.

User programs

User programs are the main programs in the call processing GP software. Every event in every call processing state of a line is assigned a processing procedure (state/event concept - see ‘Call Set-up’). Every line type is associated with a user program in the GP software. Each user program contains, in addition to procedures line type-specific conversion tables. The link between line type and User program is establislied by means of device tables. Within the user procedures, actions, which must be carried out for the current state event configeration of the line under consideration are executed or initiated immediately.

Possible actions include .

- Transmission of line signals and dialing information.

- Blocking and unblocking of lines.

- Transmission of internal messages to other user programs.

- Setting and resetting of administrable and permanent timers

- Switching of GS

- Tranmission of interprocessor messages (reports, messages, orders, etc.)

- Performing COC (cross-officc check)

- Maintenance of transient data areas (particularly call registers)

- Registering state changes in the device table.

107

4.2 LTG Safeguarding software module

The functional unit “LTG safeguarding” detects hardware faults and software errors, Which may be casual either due to any failures, or via routine tests, audits and self-supervision, in which case failture does not have to occur. In both cases, safeguarding instructs the GP or CP to initiate appropriate measures. First, a determination is made as to the effects of a fault in the operation of the switching system (failure penetration range). If a fault has already resulted in a failure, the failed device is blocked or identified accordingly, and a corresponding alarin message is sent to the CP. Service routines are provided for the transmission of alarm messages. An alarm message contains data about the type of fault. The CP uses tables to determine which measures must be taken. These measures may include :

- Signal sent to system panel (SYPD)

- Error message output to printer

- Error message written to alarm files

- Initiation of configurations

If the routine test or self-supervision has detected an error the error has not yet become visible. Routine tests detect hardware faults which have not yet affected normal operation. The tests are executed periodically, thus averting failures before they occur. Audits check the interworking and the consistency of programs and data. Self-supervision detects errors in running programs by performing validity checks. For fault clearance purposes, the faults device is configured to a different operating state. This can be done manually by entering an MML (man-machine language) command, or automatically by the CP. The possible operating states of the LTG are

ACT active

SEZ seized

CBL conditionally blocked

MBL maintenance blocked

NAC not accessible

UNA unavailable

PLA planned

After certain faults and failures, it is necessary to restart the LTG. This is initiated automaticilly by the CP. The LTG is then restored to its normal operating state.

108

4.3 LTG Adminitration soft-ware module

The functional unit “LTG administration” handles connection-related events independent of the state of the connection. Administration includes parameter administration, traffic measurement and overload handling.

Parameter administration

The tasks of parameter administration include

- Calling initialization routines, so that overload handling can be initialized during initial starts and new starts

- Loading of - zone tariff tables for call charge registration

- digit pre-translation tables, to determine the number of digits that must be sent to the CP for translation

- exchange data

- line termination data for setting up and releasing individual lines for an active LTG

- Sending overload messages to the CP

- Alleviating overloads

- Control traffic measurement

- Calling fault tables

Traffic measurement

The tasks of’traffic measurement include

- Recording the load in theGP

- Reording event on subscriber lines and incoming trunks and

- event at rceceivers

For incoming trunks and receivers, traffic measurement is initated by the user program. This is called “collective data registration”. A traffic data memory is always a signed to a group of objects (subscribers, incoming trunks, DTMF receivers, MFC receivers)

109

Overload handling

Tasks ofoverload handling include :

- Prompt detection of imminent LTG overloads and the resulting CP overloads- Initiation of overload control measures- Discontinuation of control measurs as overload subsides- Maintenance of overload statistics and reporting overloads to the CP.

4.4 LTG Operation Software module

The functional unit “LTG operations (operating system)” is subdivided into the following areas: start level, processing level, and real-time level. These structure levels are illustrated in Fig 4.2

Srart Level

The start level contains programs which initiate LTG recovery. At this point, there’is still no on-line connection to the CP. The bootstrap program is implemented in the firmware (FW) and is stored in a PROM in the GP. It starts when the supply voltage for the LTG is switched on or when the watchdog unit (WDU) expires. The bootstrap program is the means by which the CP loads the GP-software. Then the initialization program is called. This program starts the master scheduler at the processing level.

Processing level

The processing level contains and the master and service routine. Service routines assemble job block, place them in success and connection functional units of the LTG. The master scheduler executes in an endless loop and calls main routines on the basis of priority flags. The main routines process pending

Figure 4.2 : Structure levels of operating system

110

… in accordance with their priority is set by the interrupt program, the service programs or by the main routines themselves.

The real-time level is where interrupt programs execute. Interrupt programs process urgent real-time tasks by interrupting the master scheduler and the main routines.

- Real-time scanner, for hardware-controlled interrupts at 4-ms intervals

- Receive interrupt, sets priority flags; is called via DLC.

- Send interrupt, sends acknowledgments for data link control.

- Error interrupt, called if write-protection of a memory area has been violated, e.g’, instructs the safeguarding programs to process the error further.

4.5 LTG Utilities software module

The functional unit “LTG utilities” provides utility programs for detecting and correcting software errors during the installation phase of the exchange:

- The dump function is used to make a copy of the contents in the LTG memory.

- The breakpoint function can be used to set breakpoints in the code area of the GP software, with facilities to output data and modify transient data.

- The patch function is used for making on-line modifications in the code areas in the LTG.

- The LTG tracer (PDF tracer) function makes it possible to trace the sequence of line-related events in the LTG. In this way, the CP obtains line-specific data for display/logging purposes.

- The call tracer function can be used to trace the dynamic sequence of call processing traffic.

4.6 LTG PCM Carrier Processing DIU30 software module

The functional unit “LTG PCM carrier processing DIU30" performs the following tasks:

- Control of administrative and safeguarding tasks

- Initialization of all states of the DIU30 following a recovery

- Error detection within.a DIU30 via routine test and diagnosis

111

Control of adininistrative and safeguarding tasks

The control manager program controls the administrative and safeguarding tasks for the DIU30. The control manager can be used for all DIU30 in various configurations (trunks or digital line units DLU).

To avoid undefined program states, administrative and safeguarding jobs must not be processed in parts. Up to four jobs per DIU30 are stored in a memory assigned to the control manager. If additional jobs are pending, the program processes these only after the current job has been completed. The control manager processes the jobs depending on the operating state of the DIU30. When processing a single DIU30 or an entire LTG, the control manager instructs all connections for subscriber lines or trunks to execute call processing responses. All processes for the control manager execute via a pseudo device table for each DIU30.

The control manager performs the following tasks.

- O&M configuration of a DIU30

- Fault-related configuration of aDIU30

- O&M configuration of an LTG

- Overload control

- Software recovery of a line/trunk group (Initial -start LTG)

- New start of a line/trunk group (New start LTG).

- Recovery handling (Data base recovery for LTU data)

- Creation or deletion of a DIU30

- Busy/idle indication on the faceplate of the DIU30 module

- Alarm message to distant exchange

- Control in accordance with PCM30 alarms

Initialization of all states of DIU30 following a recovery,

Initialization of a DIU30 comprises procedure-specific and dynamic initialization.

112

Procedure-specific initialization performs the following tasks:

- Initializing tables

- Sending a hardware reset to the DIU30

- Initializing the control channel to the DIU30

- Setting a counter to monitor initialization

Dynamic initialization performs the following, tasks:

- Waiting for the message “DIU30 initialized” from the DIU30 or for expiration of the supervisory counter.

- Message sent to DIU30 indicating that the GP is assuming control of the DIU30

- Message regarding correct settings for the interface between the DIU30 and the GP

- Message regarding the determination of the operating mode of the DIU30

- Message regarding control of LED displays on the faceplate of the DIU30 modul.

- Initiation of routine test and diagnosis in the DIU30 for handling statistics meters

- Seting a counter to monitor loopback tests during routine test and diagnosis.

Error detection within a DIU30 via routine test and diagnosis

The primary task of routine test and diagnosis is to detect errors in a DIU30. The tests used depend on the individual D1U30 applications (D1U30 for trunks or DIU30 for DLU and PA). Table logic is used to adapt the D1U30 to the corresponding application. Some tests can be used in common by several different routine test of D1U30.

The following types of tests are performed by routine test and diagnosis for

- Routine test of DIU30 (initiated by the central routine of the process scheduler)

- Demand test of DIU30 (initiated by alarm processing DIU30 or by MML command).

If the routine test or diagnosis detects a defective DIU30 or a faulty chanel within a DIU30, it sends an error message to the CP. In the event of a central DIU30 failure (several channels defective), the routine test instructs the control manager to change the Operating state of the D1U30. For channel-specific failures in a D1U30, the routine test further identifies the faulty channel.

113

4.7 LTG Test and Measurement software module

The functional unit, “LTG test and measurement” is used for testing subscriber line and trunks. Appropriate user programs are available in the various LTGs. The following user programs belong to the functional unit “LTG test and measurement” within the GP software:

User program for testing subscriber lines

The user programs for testing subscriber lines control the following- the line workstation (LWS)

- the test unit (TU) in the DLU

- the conference equipment (CE), used for setting up and accepting test connections at theLWS.

User programs are also available for ring back service (RBS) and the subscriber line measuring system (SULIM).

User programs for testing trunks

The user programs for testing trunks control the following :- the trunk workstation (TWS)

- the automatic test equipment for trunks (ATE:T, Sect. 3. 1)

- the automatic test equipment for transmission measuring (ATE:TM, Sect. 3.1).

- the end-to-end testing, answer equipment (ETEAE)

- the conference equipment (CE). The CE is used to monitor the trunks being tested and for setting up and accepting test connections at the TWS. The ATE:TM can be connected, if necessary;

User programs are also available for system independent test equipment. e.g.:

- Trunk test equiment (TTE) atid answer unit (AU)

- ATME2

The user programs also contain the software supported answering equipment (e.g., test number automatic subscriber) and other test equipment, e.g. the test phone and ring back service (RBS).This section may be referred again while studying ‘Line and Trunk Testing’ (Training Objective 4.4).

114

5.0 Physical Design of LTGG

The number and type of functional units of an LTG depend on type of lines connected and the transmission and signaling methods used. Different line types and their combinations require LTGs with various specific equipment configurations. Only a few standard types of module frames are required to meet all requirements encountered with the LTG of the EWSD system. The packaging method used allows module frames to be equipped with various combinations of functional units.

The following sections explain the physical design of an LTGG. Fig 5.1 shows several possible configurations and combinations.

5.1 LTGG (C-function)

Digital trunks can be operated with channel associated signaling (CAS) or with common channel signaling (CCS). If register signals are transmitted with multifrequency code (MFC), CRMs are used in the LTGG.

If trunks are connected exclusively, the LTGB consists of the functional units in the SU and maximum of 4 LTUs (for DIU30, Fig 5.2), as well as the functional units GP and GSL.

5.2 LTGG (B-function)

For connection of DLU/PA (with/without trunks), the LTGG comprises the functional units GP, GSL and the functional units in the SU and in the LTUs. Up to four LTUs (LTU-0 to LTU-3) are provided for DIU30 and fifth LTU (LTU-4) can be used for CRs. In addition to CGSM and PMU, the GP contains an SILCB for connection of DLU and PA. Fig 5.3 shows the functional unit of an LTGG with connection of DLU/PA, operating at transfer rates of 2 Mbps.

Fig 5.4 shows the functional units of an LTGG with local connection of DLU via DIU:LDIB. The configuration shown has two DIU:LDIB in an LTGG: each DIU:LDIB has a 4096 kbit/s link to a DLU ( = 2 DIU30). Other configurations arc possible (e.g. combinations of’remote DLUs with local DLUs).

115

Figure – 5.1(b) : Possible LTGG configurations (Contd.)

116

Figure – 5.2 : Functional Units of LTGG (C-function)

117

Figure – 5.3 : Functional Units of LTGG (B-function)

118

Figure - 5.4 : Functional Units of LTGG (B-function)(for local connection of DLU via DUI:LDIB)

119

5.3 Module Frame Layout

The module frame for LTGG (F:LTGG) accommodates two LTGGs. An LTGG (C-function) contains (when trunks are connected exclusively) the functional units in the SU and LTUO to LTU3, the functional units GSL and GP, and the DCC (Fig 5.5).

In the LTGG (B-function) for connection of DLU/PA (with/-without trunks), an LTGG contains the functional units in the SU and LTU0 to LTU3, the functional units GSL and GP (PMU, CGSM M:SILCB), and the DCC (Fig 5.6).

Fig 5.6 shows an LTGG with local connection of DLU via DIU:LDIB; the two DIU:LDIB in LTU0 and LTU1 (in the configuration corresponding to Fig. 5.4) replace four DIU30 in LTU0 to LTU3. In other configurations, the LTUs may be equipped differently.

Figure – 5.5 : LTGG (C-function) Frame Layout

Figure – 5.6 : LTGG (B-Function) Frame Layout

120

5.2 Rack Layout

A rack for LTGG (R:LTGG) can accommodate up to five F:LTGG, i.e., up to 10 LTGs (Fig 5.7).

In the exchanges having SN(B) version of Switching Network, SN is housed .in a composite rack R:SN(B)/LTGG. In this rack one TSG/SSG will be housed alongwith 8 LTGGs. More details will be given under SN rack layouts.

Figure – 5.7 : Layout of LTGG rack

121

5.3. New version of LTG (LTGM)

Line/Trunk Group of type M has recently been developed by Siemens. An LTGM will need only 3 modules as detailed below:

New module Old module (LTGG) Function

1. lxGPLC lxPMUC + lxSMX for trunks orlxGPLSD lxPMUD + lxSMX + IxSILC for remote DLU,

PA + trunks

2. lxGSM lxGSL + lxGCG + lxTOG + 2xCR(8) + lxRM:CTC

3. lxDIU120A 4xDIU30D + lxDCCDE for remote DLU,PA + trunks

orlxDIU LDIM 2xLDIB + lxDCCDE for local DLU

6.0 O & M Aspects (For more details, please refer MMN : LTG-IN)

6.1 MML Commands for LTG Creations/Maintenance

CR LTG CAN LTG DISP LTGCR LTU CAN LTU DISP LTUCR CRMOD CAN CRMOD DISP CRMODSTAT LTG CONF LTG DIAGLTGSTAT DIU CONF DIU DIAGDIUSTAT CR CONF CR DIAG CRSTAT COU CONF COU DIAG COUSTAT OCANEQ CONF OCANEQ DIAG OCANEQ

122

6.2 Identification of LTG parameters

LTG No. : tsg – ltgtsg = Number of SN time stage group TSG (0 ……… 7)tsg = Number of LTG (1 ……… 63,

OST : Operating statuse.g., PLA, ACT, STB, MBL, CBL, NAC, UNA and SEZ

CH0 : Current operating status of message channel (SN-0 side)

CHI : Current operating status of message channel (SN-1 side)

DIU : DIU Number (0….. 3)

DIUTYP: diu type, e.g., D30 = DIU 30

APPLIC : Applicaion of the DIU, e.g.,CAS CAS = Trunk with CASCCS CCS = Trunk with CCSCAS RCA = Interconnection Digital Announcement

(DAS)CCS DLU = DLU with CCSEXT DLU = DLU without CCS

LCPOS : ltu – mod – crltu = LTU number (0 ………… 7)mod = module member (0……6) in the LTUcr = number of CR (0…………. 3) on the module

CRPOS : mod = module number (0 ……….. 7)Cr = number of CR (0…….. 3) on the module

CRTYP : Code Receiver type = type of CR (e.g CRMR2, CRPC)

CO U : COU number (0 ………… 3)

COUTYP : Conference Unit Type

OCNO : OCNO = Number of OCANEQ (0………………30

OCANEQTYP : OCANEQ equipment type

LDPARP : Load parameter, which indicates the type of software (e.g. B-function or C-function) that will be loaded into the LTG.

123

6.3 Status interrogation STAT LTG : LTG = tsg - ltg

STAT DIU LTG = tsg –ltgSTAT CR : LTG = tsg – ltgSTAT COU LTG = tsg – ltgSTAT OCANEQ LTG = tsg-ltg

124

125

6.4 Configuration

General Principle

The unit to be diagnosed must be MBL for fault clearance. If the Unit to be cleared is not MBL, it must he configured to MBL before fitult clearance. If the unit is in ACT, it should be configured first to CBL and then to MBL. When the unit has been successfully cleared of faults it should be configured back to ACT.

Configuration from ACT to CBL

CONF LTG: LTG = tsg-ltg, OST = CBL;

This command blocks the LTG for call processing, i.e. new seizures are no longer possible.

If a nailed-up connection is set up via the LTG, the warning message is given that nailed up connections will be released if configured to MBL.

Possible configuration are : ACT to CBLCBL/UNA to MBLMBL to ACT

6.5 Diagnostics

LTG diagnostics

The LTG may be diagnosed only in MBL status.DIAG LTG: LTG = tsg-ltg, TA=ALL;

The LTG must be put into operation to execute the LTG diagnostic. Accordingly, when DIAG LTG is entered, first of all configuration of the LTG to ACT is carried out and entered as operational state SEZ (seized by diagnostic).

If an LTG goes into service, in many cases the code is not destroyed, or only partly so. It is therefore sufficient just to load the destroyed code. The summation check is used to test that the code is correct. This configuration procedure is called conditional loading.

If the LTG was reset in the course of the fault clearance it has got to be reloaded because resetting formatted the memory.

126

DIAG LTG tests all central and partially central LTG units in the following order:

Test Abbreviation Test

GPU Test of modules PU/SIB or PMU (FIFO, ORAM, IRAM) and SMX (Loop-Function. Multiplexer and LAST LOOK)

GSM Testing all 512 control memory cell of the GS

GEN Power supply test

RAM Test of the supervisory circuits in memory module. For memory module PMUx, all memory bytes are checked for 1 and 2-bit errors.

CCG Test of the supervisory circuit in module GCG:LTGY

SPS Test of the GS supervisory circuit.Through-conneetion test via SPH 11Conference call test, when conference is created.

LIU Test on the central LIU functionsTest on all LIU channels (Except for channel 0)

TOG Test of the tone generator - test tones and idle tones- software windows

CR2 Code receiver test for MFC:R2

CRP Code receiver Test for DTMF dialing

CTC Test of a receiver for continuity check (RM:CTC)

DIU Test of the central DIU functions Test of the speech channel Test of the signaling channel

SIL SILC module test

COU Test of the central COU-Functions Test of the speech channels

IND Test of the central OCANEQ functions Test of the speech channelsCheck sum test of the speech fragments in the EPROMs

127

Diagnostics for sub-units of LTG

The following sub units of LTG can be tested individtrallyDigital Interface Unit : DIAG DIUCode Receiver DIAG CRConference Unit DIAG COUOperationally Controlled Announcement Eqpt. : DIAG OCANEQ

The prerequisite for carrying diagnostics on any of the above subunits isLTG = ACTorCBLDIU /CR/COU/OCANEQ = MBL

6.6 Creation of LTG /LTU/CR1. Creation of LTG

CR LTG: LTG = 0-1 Type = LTGB, LDPART = 12;2. Creation of LTU

(a) Creation of DIU 30 interface to DLU

CR LTU; LTG = 0-I, LTU = 0, Type = D30, APPLIC =CCSDLU; CR LTG: LTG = 0-1, LTU = 1, Type = D30, .APPLIC = EMPLU: ……. DLU

(b) Creation of DIU 30 interface for trunks using MFCR2 or DASCR LTU: LTG = 0-4 LTU = 0 Type = D30,

APPLIC = CASRCA (FOR…)CR LTU: LTG = 0-1 L1U= 1 Type – D30APPLIC = CASCAS ( for Trunk)

(c) Creation of LTU for purposes other than connecting PDCs

• Creation of code receivers for DTMF dialing in LTUCR LTU: LTG = 0-1. LTU =4. Type=VO3.

• Creation of Conference UnitCR LTU LTG=0-7. LTU = 3 Type = y22.

• Creation of LTU for ETEAECR LTU LTG= 0-1, LTU=3, Type = VO4, Modvar=1-0;

Creation of LTU for conference equipment for trunk line workstation (TLWS) CRLTU : LTG = 0-1, LTU = 6, Type = V08; Creation of LTU for translation function (integrated) for TLWS CRLTU : LTG = 0-1, LTU = 5, Type = V09, Modvar = 0-0 & 1-0;

128

2. Creation of CR in SUCR CRMOD : LTG = X - X, CRMOD = X, TYPE = CRMR2;

6.7 To display existing LTGs/LTUs/CRsDISP L TG L TG = 0-xLTG TYPE LDPARP0-1 LTGB 120-2 LTGB 120-4 LTGC 130-5 LTGC 13DISPLTU:LTG0-1;

LTG LTU TYPE APPLIC MOD VAR0-1 0D30CCSLDI0-l&1-1&2-1&3-1&4-l&5-1&6-l0-1 1D30CCSDLLJ0-1 & 1-1 & 2-1 & 3-1 &4-1 &5-1 & 6-10-1 2D30EXTLDI0-1 &1-1&2-1&3-1&4-1&5-1&6-10-1 3V04 0-1&1-0&2-1&3-l&4-1&5-1&6-10-1 4V03 0-I&1-1&2-1&3-1&4-1&5-l&6-10-1 5V04 0-0 & 1-0 & 2-1 & 3-1 & 4-1 & 5-1 & 6-i0-1 6V08 0-l&1-1&2-1&3-1&4-1&5-l&6-10-1 7V10 0-3&1-1&2-1&3-1&4-1&5-1&6-1

DISP CRMOD: LTG; 0-1LTG CRMOD TYPE0-1 0 CRPC0-1 1 CRPC

6.8 Safeguarding

The LTG safeguarding functions consist of:

- routine test- constant self-supervision- traffic-dependent self-supervision

6.8.1 Routine test

Routine LTG testing, in which central and decentral LTG modules are tested, is performed approximately every 2 to 3 minutes. The test sequence is as follows:

Test Abbreviation Test

129

GEN Power supply test

RAM Test of the supervisory circuits in memory module. For memory module PMUx, all memory bytes are checked for 1 and 2-bit errors.

GCG Test of the supervisory circuits in module GCG:LTGY

SPS Test of the GS supervisory circuits.Through-connection test via SPH 11.Conference call test, when conference is created.

LIU Test of the central LIU functions.Test of an LIU channel. If an LIU channel is found faulty all LIU channels are tested (specia1 test)

TOG Test of the tone generator- test tones and idle tones- software windows

CR2 Code receiver test for MFC:R2

CRP Code receiver test for push-button dialing

CTC Test of a receiver for continuity check (RM, CTC)

DIU Test of the central DIU functionsTest of a speech channelTest of a signaling channel.

SIL SILC module test

COU Test of the central COU functionsTest of a speech channel

IND Test of the OCANEQ functionsTest of a speech channelChecksum test of the speech fragments in theEPROMs.

6.8.2 Constant Self-supervision

Constant self-supervision is carried out by the supervisory circuits in various LTG modules, e.g.,

- supervisory circuit for frame synchronism (GCG, LTGY)- supervisory circuit for clock failure (GCG, LTGY)

130

6.8.3 Traffic Dependent Self-supervision

Actions triggered by call processing programs are monitored by supervisory circuits, e.g..

- supervisory circuit for setting errors (GS) - supervisory circuit for COC errors.

7.0 Abbreviations

ATE Automatic Test EquipmentATE:T Automatic Test Equipment for Trunks

(End to End Routining)ATE:TM Automatic Test Equipment for Transmission MeasuringATME Automatic Transmission Measuring and Signaling Testing EquipmentAU Answer UnitBA Basic AccessBE RC Bit Error Ratio CountingCAS Channel Associated SignalingCCG Central Clock GeneratorCCITT Internal Telegraph & Telephone Consultative CommitteeCCNC Common Channel Signaling Network ControlCCNP Common Channel Signaling Network ProcessorCCS Common Channel SignalingCDA Control Data AcknowledgmentCDI Control Data InputCE Conference Equipment (Software for Test Purposes)CEN Control EnableCGSM Clock Generator and Signal MultiplexerCOC Cross-office CheckCOUB Conference Unit, Module BCP Coordination ProcessorCR Code ReceiverCRM Multifrequency Code ReceiverCRP Code Receiver for Push-button DialingCTC Continuity CheckDAS Digital Announcement SystemDCC Direct Current ConverterDCR Digital Code ReceiverDI U Digital Interface UnitDIU:LDIB Digital Interface Unit for Local DLU Interface, Module BDIU3O Digital Interface Unit, 2048 kbit/sDLC Data Link Control

131

DLUC Control for DLU (Module)DMA Direct Memory AccessEM External MemoryETEAE End-to-end Test Equipment, Answer Equipment (Module)EWSD Digital Electronic Switching SystemF Module Frame for …..FW FirmwareGCG Group Clock GeneratorGP Group ProcessorGS Group SwitchGSL Group Switch and Interface UnitHDLC High-Level Data Link ControlINDAS Individual Digital Announcement SystemIO P Input / Output ProcessorISDN Intergrated Services Digital NetworkLIU Link Intertace Unit between LTG and SN (Module)LI UI LIU, inputLIUO LIU OutputLI UO/I LIU Output/ InputLMCP Subscriber Line Measuring Circuit processor controlledLTGG Line /Trunk unitLWS Line Work stationMB Message bufferMCH Message channelM FC Multifrequency CodeMM L Man Machine LanguageMU Merroy UnitOCANEQ Operationally Controlled Equipment for AnnouncementOCE:MUP OCANEQ for Memory Unit (PROM)OCE:SPC OCANEQ for Stored Program ControlOMC Operation and Maintenance CenterOMT Operation & Maintenance Terminal (O&M Terminal)PA Primary Rate AccessPDC Primary Digital Carrier

PDF Peripherel Debugging FacilitiesPMU Processor Memory UnitPROM Programmable Read-Only MemoryPSC Parallel-Serial Converter, Module of the Group SwitchPU Processing UnitR:. Rack for RAM Random Access MemoryRBS Ring Back ServiceRM:CTC Receiver Module for Continuity Check

132

SC/MUX Signal Converter, MultiplexerSCO/I Single Channel Output/lnputSDC Secondary Digital CarrierSDMA Secondary Digital Multiplexer, ModuleSGC Switch Group Control (Module)SIB Signal BufferSIBI Signal Buffer, InputSIBO Signal Buffer, OutputSIBO/I Signal Buffer, Output/InputSIH Signal HighwaySIHI Signal Highway, InputSIHIM Signal Highway, Input, MultiplexedSIHO Signal Highway, OutputSIHO/I Signal Highway, Output/InputSILCB Signaling Link Control. Module BSMX Signal MultiplexerSN Switching NetworkSPH Speech HighwaySPHI Speech Highway, InputSPHIL Speech Highway. Input LIUSPHO Speech Highway. OutputSPHOL Speech Highway. Output LIUSPHO/I Speech Highway, Output/InputSPHO/IL Speech Highway, Output/Input LIUSPMD Signal Processing Module, DigitalSPME Signal Processing Module, Extended

8.0 Exercises

Ex. 1.

Find out the LTGs used for B-function and the LTGs used for C-function.

Ex.2.

Write down the necessary MML-Commands to find out the current OST of all units of an LTGB and an LTGC.

133

1. LTG2. DIU3. CR4. COU5. DIU-Ports

Ex. 3.

Extend the Code Receivers of an LTGB by

(a) one Code Receiver Module in SU and

(b) one Code-receiver module in LTU-position.

Write dowr all necessary MML-CMD to create and to activate these additional Code Receivers.

Ex. 4.

Write down all the steps which are necessary to change the PMU-module of an LTGB.

Ex. 5.

Find out which LED of a DIU inform you about call-set up and conversation

134

Switching Network

What is inside ?

1. Introduction

2. General Features

3. Position and Functional Structure

4. Capacity Stages

5. Functional Units of SN

6. Switching Network (B)

7. Rack Assignment

8. Module Frame Layout

9. Interconnection of Switching Modules

10. Functions

11. O & M Aspects

135

Exercises

Switching Network

1.0 Introduction

Switching network (SN) performs the switching function for speech as well as for messages in an EWSD exchange. For this purpose it is connected to LTGs and CCNC for speech/data and to CP (through MB) for exchange of control information. Switching network with ultimate capacity upto 63 LTGs is called SN DE4. For larger exchanges SN DE5.1 is used which can connect upto 126 LTGs. Similarly SN DE5.2 can connect upto 252 and SN DE5.4 upto 504 LTGs.

136

2.0 General Features

Switching network is provided in capacity stages SN: 63LTG to SN:504LTG i.e. upto 63 LTGs can be connected, or via other intermediate capacity stages, upto 504 LTGs can be connected. The modularly expandable SN has negligibly small internal blocking and can used in EWSD exchanges of all types and sizes.

The self monitoring switching network uses a uniform through connection format. Octets (8 bit speech samples) from the incoming time slots are switched to the outgoing time slots leading to the desired destination fully transparently. This means that each bit of all octets is transmitted to the output of the switching network in the way that it appears at the input (bit integrity). For each connection made via the switching network, the octets have the same sequence at the output as at the input (digit sequence integrity). The switching network’s full availability makes it possible for each incoming octet to be switched at any time to any outgoing highway at the output of the switching network. The time slots used in switching network for making through-connection make up a 64 kbit/s connection path.

All of the switching network’s internal highways have a bit rate of 8192 bits/s (Secondary Digital Carriers, SDCs). 128 time slots with a transmission capacity of 64 kbit/s each (128x64 = 8192 kbits/s) are available on each 8192 kbit/s highway. Separate cable each containing several (eight or sixteen) such internal highways, are used for each transmission direction. All externally connected higheays also have the same uniform bit rate.

The switching network combins the numerous switching network function in a few nmodule types. These modules work at very high through connection bit rates 8192 kbits /s and some even at 32768 bits/s . For example 1025 connections can be switched simultaneously through a space stage with 16 inputs and 16 outputs. Although these highlyintegrated switching network modules switch a large number of connections with a high degree of reliability, the EWSD switching networks are always duplicated. The amount of space needed for the switching network in the EWSD exchange is still very low despite this duplication

Two different switching network versions have been supplied in India.

Switching network (SN) supplied with first 110K order

Switching network B [SN (B)] supplied with subsequent order.

137

3.0 Position and Funcitional structure

Switching network is connected to LTGs and CCNC for speech /data and to CP (through MB) for exchange of control information. Figure 1 shows the position of switching network in EWSD exchange wth reference to other equipments.

For security reasons entire SN is duplicated. The two sides of SN (SN0 and SN1) are called planes. The external highways for both transmission directions i.e between the switching network and one LTG or between the switching network and one Message Bvuffer Unit (MBU) are identified as follows as show in figure 2.

· SDC:LTG interface between SN and LTG a time slot 0 for message exchange between the LTG and cordination processor (CP) as well as between two LTGs time slot 1 to 127 for subscriber connections.

· SDC:CCNC interface between the SN and the common channel signaling network (CCNC) for common channel signaling.

· SDC TSG interface between SN and a messsge buffer unit assigned to CP (MBU: LTG) for message exchange between the CP and the LTGs as well as between the LTGs.

· SDC SGC between the SN and an MBU:SGC of the CP for setting up and clearing connection.

Switching network in EWSD exchanges uses time and space switching and therefore it is functionally divided into Time Stage Group (TSG) and Space Stage Group (SSG). SN DE4 with capacity stage SN: 63LTG has a TST structure and TSG/SSG division is not applicable in this case.

TSGs and SSGs are interconnected through internal 8 Mb/s interfaces called SDC; SSG TSGs of both planes are connected to SSGs of both planes and thus these provide further security.

Each TSG and SSG have its own Switch Group Control (SGC) that is connected to CP via MB through interfaces SDC:SGC.

138

Figure – 2 : SN Internal and External Interface

139

4.0 Capacity Stages

The present version of SN is available in capacity stages SN : 63LTG, SN : 126LTG, SN : 252LTG and SN : 504 LTG. Modular structure permits partially equipped SN. Upgradation from DE5.1 to DE5.2 and from DE5.2 to DE5.4 is possible with the help of supplier. SN DE4 is not upgradabale to DE5.1 as TSG and SSG are not separately identified in SN DE4. The traffic handling capacity, connectability for various capacity stages of SN are shown in Table 1.

5.0 Functional Units of SN

5.1 Switching path

The switching network is subdivided into time stage groupos (TSG) and space stae groups (SSG). Due to its modular structure, the EWSD switching network can be partially equipped as needed and expanded step by step. The switching networking uses the following switching stages.

· one time stage incoming (TSI)

· three space stages (SS) and

· one time stage outgoing (TSO)

These time and space stage (functional units), shown in figure 3, and located in the following module types:

· Link interface module between TSM and LTG (LIL)

· Time stage module (TSM)

· Link interface module between TSG and SSG (LIS)

· Space stage module 8/15 (SSM8/15)

· Space stage module 16/16 (SSM 16/16)

The switching network capacity stage SN : 63 LTG however has a TST structure with only one space stage as shown in figure 4. Module types LIS and SSM 8/15 are not there in SN 63 LTG. Further the modules and the TSGs/SSGs are interconnected

A list of the various modules used in SN is given in Table 2.

140

Figure – 3 : The Seven Module types in SN : DE5

141

Figure 4: The five module types in SN:DE4

5.1.1 LIL & LIS : The receiver components of the LIL, and LIS compensate for differences in propagation times via connected highways. Thus, they produce phase synchronization between the incoming information on the highways. These differences in propagation times occur because an Exchange’s racks are set up at varying distances to each other. Module LIL is connected on the interface to LTGs and has 4 inputs and 4 outputs while module LIS s connected on the interface to SSG and has 8 inputs and 8 outputs.

5.1.2 TSM : The number of TSMs in a switching network is always equal to the number of LILs. Each TSM contains one time stage incoming (TSI) and one time stage outgoing (TSO) (Figure 5). The TSI and the TSO handle the incoming or outgoing information in the switching network. Between input and output, octets can change their time slot and highway via time stages. Octets on four incoming highways are cyclically written into the speech memory of a TSI or TSO (4x128 = 512 location corresponding to 512 different time slots) The speech memory areas 0 and 1 are used alternately in consecutive 125 microseconds periods for writing the octets. The connections to be made determine the octet sequence during read-out. The stored octets are read-out to any one of 512 time slots and then transferred via four outgoing highways.

5.1.3. SSM8/15 and SSM 16/16: The SSM 8/15 contains two space stages as shown in figure 6. One space stage is used for transmission direction LIS > SSM 8/15 > SSM 16/16 and has 8 inlets and 15 outlets while a second space stage is used for transmission direction SSM 16/16 > SSM 8/15> LIS and has 15 inlets and 8 outlets. Via space stages, octets can change their highways between input and output, but they retaian the same time slot. Space stages 8/15, 16/16 and 15/8 switch the received octets synchronously with the time slots and the 125 microsecond peiods. The connections to be switched change in consecutive time slots. In this process, the octets arriving on incoming highways are “spatially” distributed to outgoing highways. In capacity stages with a TST structure, the SSM 16/16 Switches the octets received from the TSIs directly to the TSOs.

142

Figure 5 : Time stageModule (TSM)

Figure -6 : Space Stage Modules (SSM 16/16 and SSMB/15)

143

Table 2 : List of Modules used in SN

5.2 Control section :

Each TSG, each SSG and with SN 63LTG each switching network side has its own control. These controls each consist of two modules via switch group control (SGC) and link interface module between SGC and MBU:SGC (LIM)

An SGC consists of a microprocessor with accompanying memory and peripheral components. The main tasks of an SGC are to handle CP commands (such as connection setup and cleardown), message generation and routine test execution. A/ part from the interface to the message buffer unit (MBU : SGC), an LIM has a hardware controller (HWC) and a clock generator for clock distribution.

5.3 Firmware

The firmware for the switching network is permanently stored in the program memory of each SGC. For this reason, it does not have to be loaded or initialized by the coordination processor (CP) SN firmware is organized in the following manner.

· executive control programs

· call processing programs

· maintenance programs

· startup and safeguarding programs

6.0 Switching network (B)Switching network(B) is a special compact version of switching network wherein a number of functional units are integrated over a single module. This marragement has the following advantages.

· reduction in shelf space

· reduction in number of PCB types

144

· utilisation of available space in SN rack for accommodating LTGs

Functionally SN (B) is entirely similar to SN. However, only the following five types of modules are used in SN (B) as shown in table 3.

TSMB : Two LILs and two time stage modules TSMs are combined to form one TSMB

LISB : This is formed by combining two LIS functional units in a TSG

SSM8B : Two LIS and two SSM8/15 functional units in a SSG are combined to form one SSM8B.

SSM 16B This is formed by combning eight SSM16/16 functional units.

SGCB: Functional units LIM and SGC and combined to form one SGCB.

Table 3 SN (B) Modules

PCB No of cards in SN (B) 63L TG No of cards in TSG of SN (B) DE5 No of cards in SSG of SN (B) DE5 Equivalent modules in SN

TSMB 8 8 - 2XTSM

2XLILLIS - 4 - 2X LIS OF TSG

SSM8B - - 8 2XLIS OF SSG = 2X SSM 8/15

SSM16B 1 - 2 8XSSM16/16

SGCB 1 1 1 LIM +

SGC

DCCMS 1 1 1 Provided in same shelf containing Sn/TSG/SSG

7.0 Rack AssignmentBoth planes of SN:63LTG are accommodated in two frames of a single SN rack. In case of SN: 126 LTG, both planes of TSG or SSG occupy one rack each. Thus there are two racks for 2 TSGs and one rack for one SSG. SN:252 LTG and SN : 504LTG have rack assignment similar to SN : 126 LTG and occupy 6 and 12 racks respectively. Rack assignment for SN is shown in figure 7.

In case of SN (B) both planes of SN (B) of SN DE4 and both planes of TSG or SSG of SN DE5 are accommodateds in two frames of a single SN rack. However since each such frame consists of one shelf only, the balance space in the rack is utilised for accommodating LTGs. The SSG shelf can

145

accommodate two SSGs The composite rack is called rack to SN(B) Rack assignment for SN(B) / LTG is shown in figure 8

Figure – 7 : Rach Switching Network (RSN)Duplicated time stage group (TSG),

Duplicated space stage group (SSG), orBoth SN:63LTG sides (SNO and SN1)

146

Figure 8. Rack for switching network B and line/trunk group(R:SN(B)/LTG) with cable lead-in from top (left) and from bottom (right)

8.0 Module Frame Layout

147

8.1 SN : 63LTG

One plane of SN:63LTG is accommodated in one frame consistaing of two shelves. The arrangement of modules in module frame for SN:63LTG is shown in figure 9.

Figure 9 : Module Locations (SN:63LTG)

148

8.2 SN:126LTG and higher capacity stages

One TSG or one SSG of SN:126 LTG or above occupies one frame consisting of two shelves. The arrangement of modules in module frame from SN:126LTG or above is show in figure 10 (a) and (b).

Figure – 10(a) : Module Locations (TSG)

149

Figure – 10(b) : Module Locations (SSG)

150

Figure – 11(a) : Module Frame for TSG(B) (F:TSG(B)

Figure – 11(b) : Module frame for two SSG(B) (F:SSG(B))

151

8.3 SN(B): 126LTG and higher capacity stages

One TSG or two SSGs of SN(B) : DE5 (126LTG or higher capacity) occupy one frame consisting of one shelf only. The arrangement of modules in module frame for SN:126LTG or above is shown in figure 11 (a) and (b)

8.4 SN(B):63LTG

One plane of SN(B):63LTG requires one frame consisting of only one shelf. The arrangement of modules in the module frame for SN (B): 63LTG is shown in figure 12.

Figure 12 : Module Frame for SN(B):63LTG

152

Figure 13: Time Stage Group Internal connections

153

9.0 Interconnection of Switching Modules

Switching modules in EWSD switching network are connected in a manner so as to ensure nearly full availability. One module LIL, which can handle highways coming from 4 LTGs is connected to 4 inlets of a module TSM on one-to-one basis. Thus these 4 highways coming from 4 LTGs undergo a T-switching function and are then connected to inlets of 4 different LIS modules. The 8 inlets of a LIS module are connected to outlets of 8 different TSMs. Two such groups form a Time Stage Group wherein 63 LTGs can be connected. The TSG has 64 outlets coming out of 8 LIS modules. The interconnection arrangement is shown in figure 14.

Eight outlets of LIS modules in TSG are connected to 8 inlets of LIS modules in SSG on one-to one basis. One SSG consist of 16 LIS modules and therefore two TSGs can be connected to one SSG. There is again one-to one connection between 8 outlets of LIS modules and 8 inlets of SSM8/15 modules. Fifteen outlets of SSM8/15 and 16 inlets of SSM16/16 are cross connected. Similarly 16 outlets of SSM16/16 and 15 inlets of SSM15/8 are cross connected. The interconnection arrangement within SSG is shown in figure 14.

All theTSGs of SN are connected to all the SSGs in such a manner as to ensure nearly full availability. The interconnection of TSGs with SSGS in case of SN:504 LTG is shown in figure 15, and that for SN : 252 LTG and SN: 126 LTG are shown in figure 16.

Interconnection of the modules in SN DE4 is simpler as there are no TSG or SSG. The TSMs are directly connected to SSM16/16 as show in figure 17.

154

Figure 14: Space Stage Group Internal connections

155

Figure 15 : TSG-SSG interconnection for SN:504LTG

156

Figure 16: TSG-SSG interconnection for SN:252 and 126 LTG

157

Figure 17: Interconnection of modules in SN:63LTG

158

Figure 18: Speech path of a through connection

159

Figure 19 : Example of possibilities for changeover to standby in the switching network capacity stage SN:504 LTG, SN:252LTG and SN:126 LTG.

160

10.0 Functions

Three essential functions of switching network namely speech path switching, message path switching and changeover to standby are described below:

10.1 Speech path switching

The switching network switches single channel and broadcast connection with a bit rate of 64 kbit/s and multichannel connection with nx64 kbit/s. Two connection paths are necessary per single channel connection (e.g. from calling to called party and from called to calling party). For a multichannel connection, nx2 connection paths are necessary. In broadcast connections, the information is passed from one signal source to a number of signal sinks (no opposing direction).

The coordination processor (CP) searches for free paths through the switching network according to the busy status of connection paths stored at that moment in the switching network’s memory. The path selection procedure is always the same and is independent of the capacity stage of the switching network. During path selection, the two connection paths of a call are always chosen so that they will be switched via the same space stage section. A space stage section is a quarter of the space stage arrangement, with an SN:252 LTG, for examaple, this corresponds to half a space stage group SSG

After path selection, the CP causes the same connection paths to be switched through in both switching network sides of an SN. The SGCs are responsible for switching the connection paths. In a capacity stage with 63 LTGS, one switch group control paticipates in switching a connection path; however in a capacity stage with 504, 252 or 126 LTGs, two or three switch group controls are involved. This depends on whether or not the subscribers are connected to the same TSG. The CP gives every involved switch group control a setting instructions necessary for the through-connection. These setting instructions always have the same data format.

An SGC received the setting instruction from the CP via the message buffer unit MBU:SGC, the secondary digital carrier SDC:SGC and its dedieated link interface module LIM. The commands and messages between an SGC and the CP are exchanged via an LIM. The SGC calculates the setting data using the call processing programs and service routines. The SGC loads the data into registers in the hardware controller (HWC) of the LIM and, via the HWC. controls the setting of desired connection paths in the time and space stage modules (TSM and SSM). The speech path of a through connection is shown in figure 18.

161

10.2 Message path switching.Apart from the connections determined by subscribers by inputting dialing information, the switching network also makes connections between the LTG and the CP. These connections are used to exchange control information; they are setup only once, and then they are always available. For this reason, they are called semipermanent connections. Via these same connections, the LTGs also interchange message without having to burden the CP’s processing unit. In this manner, separate line netwok for the exchnage of messages within an exchange is not necessary. Nailed-up connections and connections for common channel signaling are made on a semipermanent basis as well.

10.3 Changeover to standby

All connection paths are duplicated, i.e. switched through in SN0 and SN1. This provides an alternative route for each connection in case of failure.

Figure 19 provides a simplified illustration of the various alternative routes possible in capacity stages with 504, 252 and 126 LTGs. The connection paths are switched in the same manner over both switching network sides (SN0 and SN1) The LTGs accept the incoming octets of the effective connections (subscriber/subscriber connections) from only one switching network side. In figure 19, the effective connections lead over SN0. Of note is the duplicated routing between the time stage groups (TSG) and space stage group (SSG). This makes it possible for the TSGs and SSGs to be individually switched over to standby. Switching over to standby is implemented only if errors occur simultaneously in both switching network sides. The effective connections are then lead over routed TSGs and SSGs of both switching network sides 0 and 1 . In the switching network capacity stage with 63 LTGs, it is only possible to route the connections over SN0 or SN1.

If an error occurs in the switching network, the CP initates corresponding measures for switching over to standby and issues the corresponding messages. Changeover to standby do not interrupt existing connections. Thanks to this duplication principle, all operational measures are easily carried out without impairing traffic (e.g. adding new modules or replacing defective modules.)

162

11.0 O&M Aspect;

The following MML commands are used during operation and maintenance of switching network.

Display and Modification in number of TSMs.

DISP TSG MOD TSG

Status display and Configuration commands

STAT SN CONF SN CONF TSG CONF SSG

Diagnosis and Test commands – SN DE5 and DE5

DIAG SN TEST SN

Diagnosis and Test commands – SN DE5 only

DIAG TSG DIAG SSG

TEST TSG TEST SSG

11.1 Safeguarding Concept

The switching network (SN) is duplicated. Normally one SN side is active (the SSG and both TSGs in ACT) and the other SN side is standby (the SSG and the TSGs in STB)

In the event of a malfunction in a switch group (SSG or TSG) in the active SN, the affected switch group is configured to UNA and the other switch groups in the previously standby SN are configured to ACT.

In the event of a malfunction in a switch group in the standby SN only the effected switch group is configured to UNA.

None of these reconfigurations affect switching traffic.

11.2 Fault Printouts

An SN fault printout is the result report of the fault analysis program for the SN or for a switch group (SSG or TSG). It complements the more general alarm signaling with SYP etc. i.e. whenever the

163

safeguarding system detects a malfunction in the SN, an appropriate fault printout is formulated, typically as follows:

SN FAILURE WITH CONFIGURATION MMN:SNOxx000

SGC DEFECT

FAULT LOCATION: TSG side-tsg SGC

CONFIGURATION: TSG-side-tsg FROM :zzz TO :UNA

SUPPLEMENTARY INFORMATION:

H’ zzzzzzzz zzzzzzzz zzzzzzzz zzzzzzzz

H’ zzzzzzzz zzzzzzzz zzzzzzzz zzzzzzzz

Faults affecting the SN can be divided into two groups which are clearly distinguishable in terms of the system response:

Unconditional faultThese are serious faults. The switch group in which such a fault occurs is always reconfigured to UNA. With unconditional faults, the following codewords may be output:

- SGC/SGC FAILURE

- SGC/HWC FAILURE

- PATH SET/HWC-FAILURE

- CYCLE DEFEKT

- NO CYCLE

- SGC CHANNEL ERROR

Conditional faultsThese are not serious. If such a fault occurs in a switch group with no redundancy (i.e. where the partner switch group is in NAC, UNA or MBL) then the affected switch group is not configured to UNA. If the switch group is duplicted, then it is configured to UNA, even for a conditional fault. Codewords for conditional faults are :

- SGC/PLLU-FAILURE

- SN-PLL FAILURE

- PATH SET/TSM-FAILURE

- PATH SET/SSM8-FAILURE

- PATH SET/SSM16-FAILURE

164

- SGC-DEFECT

- all COC-FAILURE

- all MCH-FAILURE

- all MUX-FAILURE

11.3 diagnositics

DIAG TSG :SN= side, TSG = tsg, TA = area, SUBUNT = TSM/SSM/CSM – x;

DIAG SSG: SN = side, SSG=ssg, TA = area, SUBUNT = TSM/SSM/CSM – x;

Explanation :· DIAG TSG

This command starts a test program, to be specified under parameter TA, for a time stage group (TSG).

· DIAG SSG

This command starts a test program to be specified under parameter TA, for a space stage group (SSG)

* side SN plane, either 0 or 1

* tsg Number of TSG, 0 to 7

* TA (test area = test program)

· area

The identifier entered for the parameter TA specifies the test program to be called up. The following test programs are possible : CHALL, ALL ,HWC, TSM, SSM, CSM, PLL.

In test program TSM, SSM and CSM, in the diagnostic command, a subunit must also be specified.

- CHALL (check all)

- for TSG, tests central sections,

- CPU with program and data memory

- PLL supervision circuit

- hardware controller

165

- tests decentral sections:

- control memory of TSM modules

- for SSG, tests central sections :

CPU with program and data memory

PLL supervision circuit

hardware controller

tests decentral section :

control memory of SSM16/16 and SSM8/15

ALL (check all control memories)

-for TSG, The control memories of modules TSM are tested. Each bit in a control memory is checked for 1 and 0. The addressing of each Ram chip in a control memory is also checked.

-for SSG The control memories of modules SSM16/16 and SSM8/15 are tested. Each bit in a control memory is checked for 1 and 0.

The addressing of each RAM chip in a control memory is also checked. Whereas modules SSM8/15 are only tested according to the SN capacity stage specified in the CP command, all 15 SSM16/16 modules are tested.

- HWC (HWC test) -for TSG and SSG

The HWC registers are checked. A good or bad message gives the states of the HWC registers and the inteface between SGC and HWC. The HWC interface to the switching modules is not tested.

- TSM (TSM test)

The addressing and functioning of each bit in the control memory of a TSM module are tested.

- CSM (SSM16/16 test)

The addressing and functioning of each bit in the control memory of an SSM16/16 module are tested.

- SSM (SSM8/15 test)

The addressing and functioning of each bit in the control memory of an SSM8/15 are tested.

- PLL (PLL supervision circuit test)

166

· - SUBUNT

For diagnositc identifiers TSM, CSM & SSM, the subunit must be specified.

Possible subunits are : TSM = functional unit TSM/LIL

SSM = functional unit LIS/SSM8/15

CSM= SSM16/16

- TSM number (0 to 15)

SSM8/15 number (0 to 15)

SSM16/16 number (0 to 14)

11.4 TestThe SN speech path test makes a cross-office check per SN side, switch group or subunit, depending on the command.

This involves setting up connections via SN, which are then tested with a test pattern. If the SN speech path detects a COC error in such a connection path, the test is repeated with a new path setup attempt (with the same parameters). If the test again detects COC error, it is terminated with FAILURE DETECTED. The MML command used is as follows, where sysmbols/parameters are same as in DIAG SN.

TEST TSG:SN = side, TSG=tsg, TA = area, SUBUNT = TSM / SSM / CSM –x;

TEST SSG : SN = side, SSG = ssg, TA = area SUBUNT = TSM / SSM / CSM –x;

12.0 Exercises1. Interrogate and find out the capacity stage of SN in your exchange. Identify its racks, frames and modules.

2. Find out the number of LTGs and TSMs in your exchange and correlate. How many additional LTGs can be provided with the existing SN configuration.

3. Change status of both planes of SNs, one by one, using all possible combinations cf OST and tabulate the results.

4. A fault in SM plane 0 has affected the third LTG connected to TSG1. What functional unit in SN could be faulty? Write MML commands to configure and diagonose the faulty unit.

167

Coordination Processor

What is inside ?

1. Introduction

2. Structure

2.1 Base processor, Call processor, IOC

2.2 Bus to Common Memory

2.3 Common Memory

2.4 Input/Output processors

3. Software

4. Rack and Module frame layout

5. Functions

6. MML commands for CP113 maintenance

7. Fault Printout (alarm message)

Exercise on CP113 maintenance

1.0 Introduction

The EWSD system consists of number of largely autonomous subsystems. The subsystems each have their own microprocessor controls, for example the controls for the digital line units (DLUC) and the groups processors (GP) in the LTGs.

The distributed microprocessor controls and the data transfer between them are coordinated by the coordination processor (CP). Fig 1.1 shows the position of the CP in the EWSD switching system.

168

Figure 1.1 : Position of the CP113 in EWSD

The CP performs the following coordination functions :

Call processing

- digit translation

169

- routing administration

- zoning

- path selection in the switching network

- call charge registration

- traffic data administration

- network management

Operation & maintenance- inputs / outputs to and from external memories (EM)

- communication with the opepration & maintenance terminal (OMT)

- communication with data communication processor (DCP)

Safeguarding

- self – supervision

- error deterction

- fault analysis

The coordination processor 113 (CP113) is supplied for all sizes of switching center. The CP113 is a multiprocessor which can be expanded progressively (by adding call processors). It satisfies all safeguarding and performance requirements exceptionally well.

The CP area also includes the system panel (SYP). The SYP indicate alarms (audio & visual) and advisories from system-internal and systm-external supervisory units.

Other important functions in the CP area are handled by :

- message buffer (MB)

- central clock generator (CCG).

2.0 Structure

The CP113 consists of a modular multiprocessor system with a processing width of 32 bits and an addressing capacity of 4 Gbytes. It is formed by the following functional units (Fig. 2.1)

170

Figure 2.1 : Structure of the CP113

- base processors (BAP)

- call processors (CAP, not included in the basic capacity stage)

- input/output controls (IOC)

- bus to the common memory (BCMY)

171

- common memory (CMY) and

- input/output processors (IOP) (for the call processing and operation & maintenance periphery)

The modular design of the CP113 means it can be easily adapted to different sizes of switching center. Its current growth capability is show in Table 2.1.

Functional Unit Minimum Maximum

BAP 2 2

CAP 0 6

IOC 2 4

CMY 64 MB 1024 MB

(Base = 4 Mbit DRAM)

IOP : MB (LTG/SGC) 2 8

IOP:MB (CCG) 2 2

IOP : MB (SYP) 2 2

IOP :MB (CCNC) 2 2

IOP : TA 2 2

IOP: MDD 2 2

IOP : MTD 1 4

IOP : SCDV 2 6 (over

IOP : SCDX - all)

IOP SCDP - 12

Table 2.1 : Growth Capacity of the CP 113

One of the two base processors operate as the master (BAPM) and the other as a spare (BAPS). During normal operation the BAPM handles all operation and maintenance functions and its share of the call processing functions. The BAPS only deals with call processing function. If the BAPM fails, its functions are handled by the BAPS instead.

172

The call processors (CAP) deal only with call processing functions. They form a redundant pool together with the BAPS. Even if one processor fails (either a BAP or CAP), the CP113 can thus still provide the full nominal load (n+l redundancy). There is no CAP in the basic capacity stage.

The two buses to the common memory (BCMYO, BCMY1) transfer and save identical information during normal operation. If a fault occurs in one of the functional units, it is disconnected from the trouble free units.

The CP113 has a 2-level memory concept. This is one of the main reasons for its high switching performance. A separate local memory (LMY) is available to each processor, in addition to the common memory (CMY). Distributing the data and programs between processor-specific memories and a common memory for all processors results in short access times. The local processor memories contain the dynamically relevant programs and the data which is only required by their own processors. The common memory contains all the common data, as well as programs and data which are not required very often.

The common memory also handles data exchanges between the processors. The stored data is supervised in the CMY and the LMYs on the basis of a check code. This code enables 1-bit errors to be corrected automatically and all 2 bit errors to be detectd, and with a high probability it also enable greater bit mutilations to be detected.

The input/output controls (IOC) coordinate and supervise accessing of the CMY by the input / output procssors (IOP). The connection between each IOC and its associated IOPs is set up by a separate bus system per IOC for input/output control (B:IOC). Up to 16 IOPs can be connected to a B:IOC.

The IOCs and the IOPs have been designed so that they can assume responsibility for the functions of the partner units if these fail. The redundant O&M data equipment (O&M periphery) is always connected to different IOCs. If one IOC or the corresponding input/output processors fail, all inputs and outputs are diverted via the partner IOC (to or from the redundant O&M and data equipment)

The O&M perophery comprises the following equipment:

- magnetic tape devices

- magnetic disk devices

- operation & maiantenance terminal

173

- data communication devices with V.24, V.28 X21/V.11 and Bx 25/x25 interfaces

2.1 Base Processor, Call Processors, Input/Output Control

Figure – 2.2 :

BAP, CAP and IOC are constructed with the same hardware components. (fig. 2.1.1) They can therefore all be described together. Each processor comprises:

- processing unit (PU)

174

- local memory (LMY)

- coupling logic (CL)

- common interface (CI)

The IOC additionally includes :

-interface for the bus system for input/output control (B:IOC)

The hardware components of the processor are connected together by means of a local bus. This bus consists of 32 data line and 32 address/control lines, and has an addressing capacity of 4 Gbytes.

The processing unit (PU) is duplicated. This redundancy enables rapid error detection and fault analysis, and thus prevents faults from spreading. The central feature of the PU is a 32-bit processor with a data width and an address width of 32 bits each. It executes the system-specific software and the function-oriented user software. It also controls the data flow to and from the input/output processors (IOP) in the IOC. PU is implemented as CPEX module.

The local memory (LMY) consists of dynamic RAM chips. It has maximum storage capacity of 32 Mbytes in the BAP, CAP and IOC (depending on the number of modules and the size of the memory chips). The LMY is organized in words with width of 32 bits. There are seven check bits for each word. The check bits are generated and checked by the cycle control card (implemented as CPCC module). The LMY is implemented as MUH module.

The LMY saves the data and the check bits in two separate memory areas. A separate control is provided for each memory area.

The coupling logic (CL) connects the two PUs of the processor together. Its main function is to compare the processing results of these PUs. If the coupling logic establishes a divergence between the two PUs, it disables the common interface (CI) of the processor to the bus to the common memory (B:CMY) and resets the processor. CL is implemented as CPCL module.

The display/control panel of the coupling logic module has four hexadecimal displays for visualizing information, as well as the some controls for the processor, namely reset button a BOOT button, a test swich and a diagnosis diplay switch.

The processor is connected to the two buses to the common memory via the common interface (CI). All common memory accesses and all interprocessor communication are effected via this interface. CI is implemented as CPCI module.

175

In addition to the hardware components common to all the processor, the input/output control (IOC) contains an interface to the bus system for input/output control (B:IOC). The input output processors are connected to the local bus of the IOC via this interface. Like the IOC, the input/output processors therefore address the various memory areas via the access control. B:IOC is implemented as IOCIF module.

Module frame for BAP/IOC

DCCMS = Direct Current Converter Module

CPCIA = Common Interface (A) Module

CPCIB = Common Interface (B) Module

CPCC = Cycle Control Module

CPAC = Access Control Module

CPEX = Processor Module

MUH = Local Memory Module

IOCIF = Bus Interface for IOC (B:IOC) Module

Figure 2.1.2 : Module frame for processor and input/output control (F: P/IOC)

2.2 Bus to Common Memory

The bus to the common memory (B:CMY) connects all the processors (BAP, CAP, IOC) both to one another and to the redundant common memory. The BCMY has been made redundant to improve safeguarding. The two BCMYs operate in parallel and handle indentical information. They may operate asynchronously in exceptional situations (split state).

176

The B:CMY has an addressing capacity of 4 Gbytes and a transmit data width of 4 bytes. The read cycles are 4 bytes long. The write cycle length is between 1 and 4 bytes.

The B:CMY operates according to a time-division multiplex method with four time slots, which can be used for information transfer. The four time slots are permanently assigned to the four banks of the common memory. Since the time slot length correspons to a quarter of the memory cycle time, all four memory banks (MYB) can be addressed during each time slot frame.

The B:CMY also handles inter processor communication (IPC) IPC cycles are not implemented using the time-division multiplex method. A menory cycle thus cannot be incorporated in an IPC cycle.

The main functional blocks of the BCMY are as follows:

- processor interface unit (one for each processor and input/out control).

- B:CMY arbiter (one decentralized stage for every four processors or IOCs and one central stage),

- BCMY controller (one),

- BCMY buffer (one),

- memory interfacc (one) and clock system (one).

The modular design of the BCMY allows it to be adapted to any capacity stage of the CP113. The functional blocks are shown in the fig. 2.2.1

177

Figure 2.2.1 : Functional blocks of B:CMY

178

Figure – 2.2.2 : Module frame for memory interface (F:MI, B:CMY in basic capacity

DCC/DCCMS = Direcct current converoer modules

PIADR = Processor interface for address module

PIDAT = Processor interface for data module

DARB = Decentralised arbiter module

CARB = Centralised arbiter module

BCTI = Bus control and tracer interface module

MIAD = Memory interface module

CMIB = B:CMY controller module

BCLK = Bus Clock system module

Figure – 2.2.3 : Module frame for processor interface (F:PI, B:CMY in expansion stage rack)

179

2.3 Common Memory

The common memory (CMY) incorporates the common database for all processors and the input/output lists for the IOPs. It has been made redundant to ensure a high level of availability. The two CMYs (CMYO, CMY1) are accessible from all the processors and input/output controls via the two buses to the common memory (B:CMYO, B:CMY1). During normal operation all read and write cycles are performed synchronously by the two CMYs. It is however also possible for the CMYs to be operate independently of the another (split mode).

The CMY is subdivided into four memory banks (MYB) and two memory con trols (MYC). The storage capacity of the CMY is currently 64 Mbytes. Each memory bank has a capacity of 16 Mbytes and is made up of 4 Mbit DRAM chips. The CMY can be expanded progressively. Its capacity limit on the basis of 4 Mbit DRAM chips is 1024 Mbytes.

In terms of the hardware, each memory bank is subdivided into a useful bit area and a check bit ares. Separate address and data buffers are provided for each memory bank area. One of the two memory controls is assigned to the user bit area and one to the check bit area.

In addtion to the memory control, the common memory contains partiy check circuits and circuits for checking and gnerating the check bit.

Data protection in CMY:

Storage modale for 16 MB (MUH) with 4Mbit chips

Data word ECC bits

0-31 32-38

Storing data (Write cycle), Error correction Code bits are calculated before storing the data word. If a processor detects a failure during a write cycle it switches over to the other bus. If still it fails then one bit error correction is performed. If two bit failure is there then a NEWSTART is started.

180

Reading data, by recalculation of the ECC bits for the read data word and comparing these new ECC bits with the stored ECC bits the CMY can detect hardware failures in its storage modules. In the read cycle also if there is a failure then a retry of read cycle is made. Still if it fails reading is performed from the other bus. If it fails again then one bit correction is done. In case of two bit error once again a NEWSTART is started. –

DCC = Direct current converters module

MUH = Memory modules

CMYMP = CMY’s main processor module

CMY1C = CMY controller module for controlling the memory cycles

CMY2C = CMY controller module for interfacing CMYMP and MUH

CMYA = Module containing circuits for addressing the CMY

CMYD = Module for controlling the data flow between B:CMY & MUH

Figure 2.3.1 : Module frame for common memory (F:CMY)

181

2.4 Input/Output Processors

Various types of input/output processors (IOP) are used to connect the CP 113 to the other subsystems and functional units of the switching center, as well to the external mass storage devices, the O&M terminal, the operation & maintenance centre. (OMC, via data lines) and the computers centers (via data lines). The following IOP types are used in the CP 113 (Fig. 2.4.1):

— input/output processor for message buffer (IOP:MB),— input/output processor for time and alarms (IOP:TA),

— input/output processor for magnetic disk device (lOP:MDD),

— input/oulput processor for magnetic tape device (IOP:MTD),

— input/omput processor for serial, data communication devices (lOP:SCD)

The minimum and maximum numbers of the various IOPs which can he connected to the CP 113 are shown in Table 2. 1. If more than one IOP of the same type is used, they must be connected to different IOCs to improve safeguarding (e.g. connect the two IOP:TAs to IOCO and IOCI).

Apart from the microprocessor, the main components ot the IOPs are the EPROM and RA M, the timers, the interrupt handlers, the interface to the B :IOC and one or more interfaces to the peripheral units.

The IOPs are initialized by the BAPM. The control programs of the IOP:MB and the IOP:SCDP are reloaded from the CMY. The control programs of all the other IOPs are stored in the EPROM. The BAPM issues commands to the IOPs, which process and executc them autonomously.

182

Figure 2.4.1 : Structure of input/output system with IOCs

183

* Input/output processor for the message buffer

The input/output processors for message buffer (IOP:MB) serve as the interfaces between the CP113 and the other subsystems and functional units of the exchange. The following functional units are connected to IOP:MB.

- messag buffer groups (MBG),- center creck generators (CCG),- common channel signaling network controls (CCNC) and- system panel (SYP).

All the subsystems and functional units are supplied via two IOP:MBs to improve safeguarding. If one of the two IOP:MBs fails, all data exchanges are handled by its partner.

* Input/output processor time and alarms

The input/output processor for time and alarms (IOP:TA) contains the hardware clock of the CP113 and interfaces to the CP racks, via which it can record alarms, e.g. fan alarms.

* Input/output processor for magnetic disk device

A magnetc disk device is connected to the CP113 via the input/output processor for magnetic disk device (IOP:MDD). The IOP:MDD has an ANSI SCSI interface for controlling the device.

* Input/output processor for magnetic tape device

A magnetic tape device is connected to the CP113 via the input/output processor for magnetic tape device (IOP:MTD). The IOP:MTD has an industry standard interface (Pertec) for controlling the device. It allows magnetic tape devices to be read and written using either the phase encoding recording method (PE) or the group-coded recording method (GCR).

* Input/output processor for serial data communication devices

The input/output processor far serial data communication devices controls data exchanges between the CP113 and the data equipment. Three different versions are available namely.

184

- with V.24/V.28 interface (IOP:SCDV)

The input/output processor for serial data communication devices with a V.24/V.28 interface (IOP:SCDV) can he used to connect either four data lines or three data lines and one operation & maintenance terminal to the CP113. The data lines can be operated at a transmission speed of up to 9.6 kbit/s. The operation & maintenancc terminal (any PC using processor 80386 or above) is used to operate the system in local mode. It is combined with a printer.

— with X.2 1/V.11 interface (IOP:SCDX)

The input/output processor for serial data communication devices with an X.21/V.l 1 interface (IOP:SCDX) can be used to connect four data lines to the CP113. The data lines (HDLC UNC-2-4 procedure) can be operated at a transmission speed of up to 64 kbit/Sec.

- with BX.25/X.25 interface (IOP:SCDP)

The input/output processor for serial data communication devices with a BX.25/X.25 interface (IOP:SCDP) can he used to connect two data lines or OMT-PCs. to the CP113. The data lines (LAPB procedure) can be operated at a transmission speed of up to 64 kbit/s. IOP:SCDP is not a single card but a set of cards known as LAUB & LCUB.

Module frame for IOP

Figure 2.4.2 : Module frame for input/output processor (F:IOP)

185

Figure – 2.4.3

186

Figure 2.4.4

187

Figure 2.4.5

188

3.0 Software

The EWSD software is 100% modular. The software functional units form the top level of the hierarchy. Each software functional uuit is made up of logically related subsystems. The subsystems are in turn subdivided into one or more modules. The modules are the smallest software units. They implement the procedures, processes and data.

The processor concept of the CP113 is based on a distribution of functions between the base processors (BAP) the call processors (CAP) and the inputloutput controls IOC. The BAPM and the BAPS have the same software functional units (Fig. 3.1). The CAPs contain mainly software for performing their call processing functions. The IOCs only contain firmware.

Figure 3.1 : Software in the processor of the CP113

The CP organization functional unit of the CP software comprises the operating system and the loader. Each processor in the EWSD has its own operating system. The capabilities of the operating system are dependent on the functions performed by the processor and the resources it is required to administrate. All the operating systems must perform their functions under real-time conditions. They are therefore interrupt driven under real time conditions The software necessary to operate an exchange is stored in load libraries (loadlibs) on the system disks, and must he transferred to the CP using the loaders in the programs. Some of the loades are loaded in the common memory of the CP during the bootstrap procedure. The other programs required to start the processor are stored in a PROM (programmable read-only memony)

The CP input/output control functional unit of the CP software is responsible for physical input/output (PIO), logical input/output (LIO), message exchanges between the CP user processes and the call processing periphery (IOCP), file control (FCP) and the update function.

189

The functions of the CP safeguarding functional units of the CP software are firstly to isolate and eliminate faults in the system, and secondly to set a workable configuration after system recovery.

The CP call processing functional unit of the CP software is responsible for the central call processing functions (e.g. digit translation, routing administration). Its tasks include sending setting instructions to the switch group control and to the GPs in the LTGs.

The CP administration functional unit of the CP software processes the administrative MML commands and saves. The charge, statistical and traffic data in the external memories. This data is made available by the call processors. The CP sends messages to the peripheral processors for further processing.

The CP maintenance functional unit of the CP software processes messages concerning measurement, test and diagnostic results of the LTGs. It processes the system-internal alarm messages and MML commands which ensure trouble-free operation. This functional unit is also responsible for indicating faults on the system panel (SYP) and generating audible alarms if necessary.

The CP utilities functional unit of the CP software makes test programs available for error location, analysis and correction in the software.

190

4.0 Rack and Module Frame Layout

Fig. 4.0 shows the equipment in the CP 113 racks.All the racks are compact and designed to allow heat dissipation. The slide-in fan modules in the racks take in ambient air either through the slits in the rack doors or through a raised floor, and blow it up between the modules.

Figure 4.0 : Racks for CP113

191

5.0 Functions

5.1 Call Processing Functions

The most important call processing functions of the CP are as follows:- digital translation,- routing administration,- zoning,- path selection in the switching network,- call chage registration,- traffic data administration,- network management.

The call processing functions are implemented in the CP call processing functional unit of the software. The results of the call processing activities, such as the charge and traffic data, are recorded and administrated by the CP administration functional unit.

The call processing process in the CP is run in an endless loop. It receives the messages which are sent to it, processes them and sends commands to the appropriate devices. Most of the time, the call processing process is required to deal with several parallel tasks.

When handling several calls simultaneously, the call processing process uses memory areas to store the transient data for future call control. The transient data includes the states of the current calls.

The messages, e.g. “seize calling party”, are supplied from a group processor via the input/output processor for the messages buffer to the input list for call processing messages. The current process in the CP is interrupted at regular intervals, and a call processing message is transferred from the input list to the call processing process. The message is processed by means of a state/event combination: the stored state of a subscriber line or a interoffice trunk is combined with the new event, and the corresponding processing procedure is invoked. The state changes if the event is processed successfully.

The next call processing event encounters the new state. This combination causes another processing procedure, which corresponds to the new state change, to be invoked. The connection is set up progressively in this manner and finally completed. It is cleared down again analogously.

192

The call processing functions are described in detail below:

When a connection is set up a digit block (of the dialed digit) is transferred to the CP by the LTG. The CP performs a digit translation using these digits. The result of digit translation is the desired destination. If the call is an external one, the CP subsequently determines an idle trunk to the destination with the aid of the routing administration function.

The zoning function of the CP determines the zooe in which the destination is located. The current tariff for call charge registration is determined from the zone in the line/trunk group.

A connection must then be set up from the calling subscriber line to the desired destination via switching network. The busy or idle status of the switching network is saved in the database of the CP for this purpose. The path through the switching network is determined by path selection function. The switch group control is informed of this path data by means of command via an output list and the input/output processor for the message buffer.

The call charge registration function is distributed between the line/trunk groups and the CP. The line/trunk group sums up the meter pulses during a call. The meter pulses determined in the line/trunk groups are transmitted to the CP either at the end of the call or at regular intervals in the case of long call. The CP saves the meter pulses in the ca1ling subscribers personal meter. It makes the charge data available for further processing when instructed to do so by the operating personnel.

The traffic data administration function are subdivided into traffic measurement, traffic supervision. traffic observation and traffic structure measuremnent. The traffic data is crucial to the carrier for traffic handling and traffic forecasting. Several traffic data administration programs are available in the CP. These programs gather and process the traffic data of all the different areas of the switching center and the trunk groups.

The network management function protects the network and the switching center against overload condition, or if they do become overloaded, takes suitable steps (traffic restrictions) to prevent the network from collapsing. The function also permits traffic to be distributed flexibly between the available paths and trunk groups, according to specific criteria.

193

5.2 Operation & Maintenance Functions

The operation & maintenance terminals (OMT) in the operation and maintenance center (OMC) are the access points for all operation and maintenance functions. A local OMT is provided in the switching center for performing these tasks.

The OMTs in the operation & maintenance center are connected to the CP113 either via the data communication processor (DCP) and data lines or directly via the IOP:SCDP. The local OMT is also connected to the CP directly.

The standard man-machine language (MML) of the CCITT is used for the dialog between the operating personnel and the CP. The CP controls the dialog with OMT and checks that commands are entered correctly

The operation and maintenance functions are incorporated in the CP administration and CP maintenance functional units of the software.The operating

- procedures for the many different tasks which can he handled via the OMT are described in separate operation manuals.

5.3 Safeguarding functions

The CP contains, number of safeguarding programs the CP safeguarding functional Unit of the software, which are designed to ensure the operability and availability of the switching center. These safeguarding programs analyze both faults affecting the CP itself and faults in the other subsystems. The safeguarding software in the CP does not merely respond to faults, but also starts test and diagnostic programs. The functions of the safeguarding programs are to:

- determine and set a workable configuration after system recovery,

- record and process safeguarding messages from the periphery and the CP processes.

- -control the perodic test procedures,

- evaluate the alarm messages from the supervisory circuits in theCP,

- gather and save fault symptoms,

- analyze and localize faults,

194

- restore a workable system configuration after a hardware fault,

- eradicate the consequences of software errors by means of adequate recovery actions, if these errors cannot be cleared by the user programs themselves.

Three different recovery types are implemented in EWSD. They are as follows:

* Installation recovery

An installation recovery is performed when the system is put into service during an initial installation, APS change or restoral procedure (e.g. after a power failure).

* Central recovery

A central recovery is performed in order to restore call processing operation after fault in the coordination processor area. It includes recovery action which clears a fault during operation (both hardware faults and software errors) and restores the full call processing capabilities immediately.

* Peripheral recovery

A peripheral recovery is performed when units belonging to the call processing periphery are returned to service after a fault. It includes all recovery action which clears a fault during operation (software errors) and makes the unit concerned available to the system again. The call processing peripheral units in which a peripheral recovery takes place include LTG, DLU and CCNC.

6.0 MML Commands for CP 113 Maintenance

6.1 State Interrogation commands:

Command STAT SSP is used to interrogate the operating states of all CP-113 units (Central units, peripheral units, input/output processors, air circulators). The result is a list, in columns, showing the units and their states. Functional units that have been taken out of system operation (due to an alarm or manually) are marked with star in the list.

Command SRCH SSP is used to search for units in one of the operating states given in the command. Output is in the form of a list.

Syñtax of the command is:SRCH SSP: OST = ACT/MBL/SEZ/NAC/UNA/SPR;

195

6.2 Configuration Commands:

The configuration handler is responsible for assigning an operating state to configurable units that corresponds to the physical availability of the unit. The configuration commands are used to set the operating states of CP units.

* Configurable central units commands:CONF BAP Base processorCONF CAP Call/processorCONF IOC Input/Output ControllerCONF CMY Common memoryCONFBCMY Bus to common memory

* Configurable peripheral units commands:CONF IOP Input/output processorCONF IOPG Input/Output processor groupCONF CSC Central service channelCONF MDD Magnetic disk driveCONF MTD Magnetic tape deviceCONF OMT Operation & Maintenance terminal

Syntax of the commands will be

CONF <unit>: unit = no., OST= ost [DIAG=J] [ SUP] ;

unit = no Number of unit to be configured

OST ACT/MBL Operating state

DIAG YES/NO If YES is input, daignosis is performed

SUP =YES/NO If YES is input, output of progress message is supressed

CONF lOP: lOP <ioptype> — <iopno>, OST = ost;

iop type

iop type = IOPSCDV IOP forOMTandCSCIOPSCDX IOP for csc

IOPMDD IOP for magnetic disk

IOPMTD IOP for magnetic tape

IOPMB IOP for message buffer

IOPTA IOP for time and alarms

OST = ACT/MB L/PLA Operating state

196

If a unit could be configured as specified in the command, the associated output contains the acknowledgment EXECD and the operating states before and after configuration.

The outputs from executed CONF commands are also written into the HF. ARCHIVE file.

It is possible for units to be marked as NAC in the system-internal configuration table. This means that unit in question is in ACT but is not accessible because the preceding unit has a state other than ACT.

No test is executed when the devices are configured back to ACT.

COM BAP

This command is used for switchover. It is a dangerous command. Before the execution of time command a question will be sent to operator tbrough MMl.

197

6.3 Commands for IOP:MB creation:

The table given in the prepage is used for the creation of IOP:MBs in the CP113. As mentioned in the table the physical address and logical address of the MB will be used for creation of IOP:MBs.

Let us take the example of the training exchange. In the training exchange we have to provide IOP:MBs for following units.

1. IOP:MB for the one message buffer group (MBG)

2. IOP:MB for the one CCNC

3. IOP:MB for the CCG

4. IOP:MB for the SYPC

198

These IOP:MB. has to be created according to the physical & logical address relation ship as explained in the table given on the prepage. Let us now see the MML commands required for the creation of various IOP:MBs.

* Creation of IOP:MB for CCG -

Since we have got two IOCs we have to create two IOP:MB for CCG, The commands used will be.

CR IOP: IOC = 0, BIOC = 09, IOP=IOPMB-40, SUBST=IOPMB-41;

CR IOP: IOC = 1, BIOC = 09, IOP = IOPMB-41, SUBST= IOPMB-40;

In the above commands the value of parameter BIOC indicáte the physical address of the IOP:MB whereas the value of the parameter IOP & SUBST (substitute IOP) indicate the logical address of the IOP:MB.

* Creation of IOP:MB for SYPCCreation of IOP:MBs for the SYPC will be done with the help of following commands.

CR IOP:IOC=0, BIOC=10, IOP = IOPMB-42, SUBST=IOPMB-43

CR IOP:IOC=1, BIOC=10, IOP = IOPMB-43, SUBST=IOPMB-42;

In these commands also the parameters BIOC and IOP & SUBST have the values of physical and logical address as explained in the table at the prepage.

* Creation of IOP:MB for MBG

In EWSD system we can have maximum four MBGs. This means we will require four sets of IOP:MB to be created. In our training model exchange since we have only one MBG so we have to create only one set of IOP:MB. Following commands will be used.

CR lOP: IOC=0, BIOC=00, IOP=IOPMB-32, SUBST= IOPMB-33;

CR lOP: IOC=l, BIOC=00, IOP=IOPMB-.33, SUBST= IOPMB-32;

Once again all the parameters have usual meanings as explained earlier. If we have more number of MBGs the other sets of IOP:MB can be created with the help of table explained earlier.

199

* Creation of IOP:MB for CCNC

At present in the EWSD only one CCNC( duplicated) is provided. We have to create only one set of IOP:MB for CCNC using following commands.

CR IOP: IOC=0, BIOC=04, IOP=IOPMB-00, SUBST= IOPMB-0l;

CR IOP: IOC=1, BIOC=04, IOP=IOPMB-00, SUBST= IOPMB-0l;

All the parameters have the usual meanings.

After we create all these IOP:MBs ( for CCG, CCNC, MBG, SYPC) we have to configure them in MBL state and then in ACT state.

6.4 System Splitting Commands

* SPLIT SSP

This command is used to split the system. When the system is split the BAP spare is the non switching BAP. The syntax of the command will be

SPLIT SSP : [, [TEST=] [, SUP=]]:

TEST = YES / NO If YES is input all active CP units are tested before the system is split.

SUP = YES/NO If YES is input, output of progress message is suppressed.

MERGE SSP

This command is used to cancel the split state of the system. An automatic short test is performed on the input/output processors before they are reunited with the system, peripheral devices are reunited without diagnosis. The syntax of the command will be :-

MERGE SSP: [, [ TEST = ] [, SUP=] ]; TEST = YES / NO If YES is input, the central units of the non-switching part of the system are diagnosed before it is merged with the ………of the system. S = YES / NO If YES is input, output of progress message is suppressed.

Device Commands :

200

INIT MD This command is used to format disks on MDD. The device must be MBL. It is a dangerous command. The syntax of the command will be.

INIT MD: MDD = 0/1; DISP MD This command is used to display the contents of the disks on both MDDs.

INIT MT This command is used to initialize a magnetic tape device i.e. generate the VOL label. The syntax of the command will be

INIT MT : VSN = …., CD = ….., [, OWNER = X ], VSN = ….. MTD = xx VSN = Volume serial number CD = EMCDIC/ISO Code OWNER = Owner MTD = 0/1 Magnetic tape device no. DISP MT

This command is used to display the VOL label of the specified magnetic tape device. Syntax of the command will be

DISP MT: VSN = , MTD = no.;

VSN Volume Serial number

MTD 0/I Magnetic tape device number

6.6 Diagnostic Commands:

The diagnostic command starts single or multiple diagnostic runs or a permanent test (cyclic) of the central units and some of the peripheral. No diagnostic command is executed unless the unit in question is in MBL.

* Diagnosable central units commands

DIAG BAP Base processor

DIAG CAP Call processor

DIAG IOC Input/Output control

DIAG CMY Common memory

201

DIAG BCMY Bus to common memory

* Diagnosable peripheral units command :

DIAG IOP Input/output processor

DIAG IOG Input/output processor group

DIAG MDD Magnetic Disk Device

DIAG OMT Operation & Mtce. Terminal

* Nondiagnosable peripheral units:

CSC Central service channel

MTD Magnetic Tape device

6.7 Testing command:

Only units in ACT can be tested. These units are configured to SEZ by the test programs, i.e. the unit is taken out of service.

There are four different type of tests:

- demand test

- routine test

- consistency test

- system status analysis

All test commands except those for the IOP are treated as dangerous. There is no test command for the central service channel.

Demand Test:

The demand test is used in fault clearance. Commands used for demand test are:

TEST SSP

202

This command is used to test all the units in ACT.

TEST IOP

This command is used to test the IOPs.

Routine Test:

The actions taken for fault detection are based on the assumption that only one, fault can occur in a unit at any one time. To concept of fault detection is to reduce the probability of simultaneous occurrence of several faults by periodically testing unused or seldom used units by routine test programs

Routine tests run automatically at predefined times. Inputs at the OMT determines which test should be run when. Examples of commands for routine test are:

CUT SSPRT Re- enable inhibited routine test

MOD SSPRT Modify routine test data

ALLOW SSPRT Allow routine test

DJSP SSPRT Display routine test data

INHIB SSPRT Inhibit routine test

Consistency Check:

The consistency check checks the consistency of HW/SW settings. Command used for this purpose is:

ACT SSPCONCK

This is a dangerous command. In the event of error, an SWSG (safeguarding software) call to system status analysis may cause a NEWSTART.

System Status Analysis SSA:

System status analysis serves to detect faults which have not been detected by a demand test.

203

One of the tasks of system status analysis to maintain the performance of the system by attempting to restore failed units to service

Fault patterns handled by system status analysis are:

- too many call processors failed

- inconsistency between HW switches (inhibit bits) and the corresponding SW image in the configuration table

System status analysis is started:

- automatically after every configuration that impairs the availability of the system.

- periodically at fixed intervals

Units which have failed due to statistics crash caused by sporadic errors are not configured to ACT Units that have previously been configured to UNA are also not configured to ACT

Command used for this purpose are:

ALLOW SSA

This command is used to allow system status analysis to make attempts to reinstate failed units.

MOD SSA

This command is used to modify the time between cyclic reconnection attempts. Intervals between 15 and 300 minutes can be specified.

7.0 Fault Print Outs (Alarm Messages)

204

Hardware fault analysis initiates the output of trouble messages with indication on the system panel . This provides a reference to a fault clearance procedure ( available in the relevant maintenance manual e.g. MMN:CP). All faults lead to an entry in the alarm register of the affected unit and to the inhibit bits to be set for the unit.

A CP113 fault print out always contain an MMN number, which refers to the fault clearance procedure in the MMN, ( register FC), with which the fault clearance should be started.

Before starting fault clearance, the CP 113 unit identified as faulty must be configured to MBL, because fault clearance can only be performed on units in this operating state.

Operating state MBL is also the prerequisite for starting and executing diagnosis. Diagnostic command are only accepted by the system for unit inMBL.

Ana1ysis of the diagnostic results in the fault clearance procedure provides a selection of suspect modules. Diagnosis is called again at later stages of fault clearance to check whether the trouble is still present or has changed or has been eliminated by the previous fault clearance step ( e.g. module replacement).

205

Example of an Alarm message :

206

Explanation of the sample fault message ( printout)

* MMN-CP750-000

CP750 is number of the fault clearance procedure to be used

* POWER FAILURE

This is the cause of the fault. It will consist of maximum 30 characters

* CONFIGURATION BCMY-1 FROM ACT TO UNA

The unit configured and the change in its operating state are shown here

* SUBSEQUENT UNITS

Other affected units due to this fault will be shown here with their unit members

* FAULT INFORMATION

The fault information output here is in hexadecimal code and is used as reference for special fault clearance.

UNIT OST ALR

The suspect unit is given under UNIT, the operating state at the time of the alarm under OST and the contents of the alarm register in hexadecimal code under ALR (reference for special fault clearance).

207

EXERCISES ON CP113 MAINTENANCE

1. Display all subunits of CP 113

2. Perform following configuration jobs.

a) BAPM to MBL

b) IOPMDD0 from the ACT to MBL

c) OMT0 from ACT to PLA.

Display all subunits of CP113 which are in MBL

Find out the units which are in status NAC.

Check the LED of the B:CMY which indicate disconnected processors.

Put back the units into ACT state.

3. Give the following commands

a) DISP IOP: IOP= IOPSCDV-X

b) DISP IOP: IOP = IOPMDD-X

c) DISP IOP: IOP = IOPMB-X

Evaluate the output of the command.

208

Message Buffer

What is inside?

1. Introduction

1. 1 Message Routes in EWSD

1.2 Functions for handling message traffic

1.3 Connection of MB to other units

1.4 Some special features of MB

2. Structure

2. 1 Message Buffer Group

2.2 Interfaces between MBG and CP/GP/SGC

2.3 Command and Message Types

2.4 Firmware

2.5 Capacity Stages

2.6 Rack and Module frame Iayout

3. O&M Aspects

3. 1 Identification of MBU Numbers

3.2 Reporting MB Funds

3. 3 Safeguardling and Fault clearance

3.4 MML commands for O&M

3.5 Tests

3.6. Preventive Maintenance

4. Exercises

Solutions

209

Message Buffer

1.0 Introduction

The message buffer B (MB(B)) is assigned to the Cf. area of the EWSD.

Functional units of the message buffer MB) have the job of controlling

message exchanges between the following subsystems.

• between the CP and the LTGs:

Call processing messages to set up circuit connections,

administrative and safeguarding or maintenance messages

• between the LTGs themselves:

Call processing messages

• between LTG and the CCNC:

Call processing messages between exchanges

via common channel signaling links

• between CP and switch group contro1 (SGC):

Setting instructions for switching network.

Depending on the source and destination of the control information, the following terms are used to describe the exchange of data.

— Data transfer from the CP to a GP : Command

- Data transfer from a GP to the CP : Message

- Data transfer from a GP to another GP: Report

— Data transfer between CCNC and GP : Order

210

1.1 Message Routes in EWSD (Fig 1)

The message routes in EWSD form a two-layer star network, with the input output processor for message buffer (IOP:MB) representing the central point.

The processors of the SYP, CCNC, MBU, CCG and CP devices are interoconnected via the first layer of the star network. The IOP:MB has output lists in the common memory (CMY) of the CP. Here there are output lists for SYP, CCNC, MBU and CCG. There is an input list for input from the call-processing periphery and an overflow list for messages.

The second layer of the star network is located after the MBU:LTG. In this layer, message arc distributed between or collected in the MBU and LTG with the aid of the SN. The MBU:SGCs implement the exchange of messages with up to three SGCs.

Communication between the GPs or DLUC and the CCNC (without the participation of the CP processing unit (PU) is made possible by a transfer list for the CCNC and for each MBU in the common memory (CMY) of the CP.

The IOP: MB has direct access to the CMY of the CP.

211

Figure 1 : Two Layered Star Network for Message Routes in EWSD

212

1.2 Functions for Handling Message Traffic

All processors participating in the transport of messages perform the following functions for handling messages :

- transport

- distribution and collection

- buffering

- saving

Distribution and collection require a speed adjustment to be made between message inflow and outflow. This adjustment is made with the aid of buffers in the MBU and IOP:MB.

Messages to be processed may have to wait for processing, since the processing processes can be “in progress”. For this reason, buffers for the processes are also needed to adjust the transport speed to the processing speed.

Message queues can form in the buffers. This ensures flexible speed adjustments between message transport, distribution and processing.

The MB(B) has been designed to meet the higher performance demands of the CP113.

The MB(B) in itself is fully redundant and is made up of an MB(B)0 and an MB(B)1. These operate on a load-sharing basis. Fig. 2 shows the tie-in of message buffer to its environment.

1.3 The MB(B) is connected to the other units as follows :

* with the LTGs each via one 64-kbit/s channel on the secondary digital carriers (SDC:TSG, SDC:LTG).

The relevant multiplex highway channels are linked to each other in the switching network via semipermanent connections. Normally the connected LTGs are distributed equally over both system halves (MB-1/SN/side 1).

* With the SGCs via multiplex highways (SDC:SGC)

213

* with the input/output processors (IOP:MB) of the CPvia the bus systems B:MBG0 and B:MBG1.

- In the input direction, the MB(B) can receive

- message from the LTGs and the SGCs (for the CP)

- reports from LTGs (for other LTGs).

- orders from the LTGs (for the CCNC)

It processes these for transmission to the IOP:MB of the CP, stores them and passes them to the IOP:MB on request.

In the output direction, the MB(B) can receive

- commands from the CP (for the LTGs and SGCs)

- reports from the LTGs (for other LTGs)

- orders from the CCNCs (for the LTGs)

It processes these for transmission on multiplex highways to the LTGs and SGCs.

214

Figure 2 : Position of duplicated MB in EWSD

1.4 Some special features of the MB(B) :· Load sharing and a high level of reliability due to redundancy

· Control of broadcasting and collective connections :

A specific software (load type) is carried simultaneously to all LTGs with the same functional structure via broadcast links during initial start or system recovery. In the case of collective connections, the same commands are sent simultaneously to certain LTGs, e.g. tariff switchover.

· Control of multi-broadcast connections, i.e.up to 16 load types can be simultaneously distributed to the LTGs.

· High transmission performance (1300 MSU/s for each transmission direction, 128 byte/message)

· Modern technology (TTL-ALS and TTL-FAST)

· Microprocessor control with permanently stored software (firm ware)

· Self-monitoring

· Simple growth capacity in stages

215

2.0 StructureDepending on the capacity stage, the M B(B) will consist of one to four duplicated message buffer groups (MBG). MB-0 contains the MBG-00,01,02,03 and MB-1 contains the MBG-10,11,12,13. Each non-duplicated MBG is installed in one module frame.

2.1 Message Buffer Group (MBG)An MBG is made up of the following functional units (fig. 3) :

* 2 nos. of MBU:LTG (Message buffer unit for LTGs)

* MBU:SGC (Message buffer unit for Switch Group Control)

* CG (Group clock generator)

* MUX (Multiplexer – forming the interface to the SN)

* Interface adapter to IOP:MB

216

Figure 3 : Structure of a Message Buffer Group (MBG) of an MB

(a) MBU:LTG (Message buffer unit for LTGs)

The MBU:LTG consists of a maximum of four transmitter/receiver controls (T/RC) and a message distribution module (MDM). The T/RC module can supply up to a maximum of 16 line/trunk groups (LTGs). One MBU:LTG will therefore allow expansion of an exchange in stages of 16 LTGs. A maximum of four T/RCs of an MBU:LTG can be interconnected via a message distribution module. This module distributes the messages arriving from the IOP:MB to a particular T/RC module and collects the messages injected by the LTG into T/RC modules, in order to transmit them to the IOP.

The MBU:LTG has the following tasks :

- Distributing and forwarding outputs (commands, reports, orders) from the CP to the LTGs.

- Collecting inputs (messages, reports, orders) from the LTGs and forwarding these to the IOP:MB and thus to the input and transfer lists of CP.

- Detecting and executing internal MBU commands from the CP, e.g., disconnecting a specific message channel.

- Forwarding messages relating to internal MBU processes to the CP, e.g., a specific message channel has been disconnected.

- Carrying out the special broadcasting function. During broadcasting, the same information can be transmitted with only two broadcasting commands from the CP to all the LTGs. A case in point might be, for instance, where software is reloaded into the RAM memory of the GPs in the LTGs.

- Carrying out the special collective command function. By means of a collective command, the same messages can be transmitted to certain LTG groups, e.g. switching to a new tariff.

(b) MBU:SGC (Message buffer unit for switch group control)

The MBU:SGC is combined into a common module (IOPC) with the interface adapter to the IOP:MB. In principle, an MBU:SGC has the same structure as an MBU:LTG. But because it only supports a maximum of three control channel pairs, the message distribution module (MDM) in this case is dispensed with. The three channel pairs, one for each transmission direction on three different

217

highways can be associated with up to three different switch group controls (SGC) in the switching network. Incoming and outgoing messages via the three channels (control information and acknowledgments) are exchanged directly with the IOP:MB via output or input FIFOs.

The MBU:SGC performs the following tasks :

- buffering commands from the CP and distributing and forwarding these to a maximum of three switch group controls.

- Buffering messages from the switch group controls and forwarding these to the CP.

- Identifying and executing internal MBU commands from the CP.

- Forwarding messages relating to internal MBU operations to the CP.

(c) Group clock generator (CG)

Every MBG contains a group clock generator (CG). It is accommodated in one module (CG/MUX) together with the multiplexer and performs the following tasks :

- Generating the exchange clock pulse of 8192 kHz and the 2-kHz frame mark bit (FMB) used for synchronization.

- Receiving the master clock (8-kHz) from one of the two central clock generators (CCG(A)). The master clocks synchronize the clocks generated in the CG. The first MBU:LTG of an MBG monitors the CG and signals alarms to the CP.

The exchange clock and the frame mark bit are forwarded to the MBU:LTG or the MBU:SGC, which in turn transmits these together with the transmit data to the switching network for onward routing to the LTGs or the switch group control (SGC). The GCG in the SGC synchronizes the clocks it has generated with the aid of the incoming clocks and transmits these to the switching network. From here they are retransmitted to the MBU:LTG with the data received by the LTG.

The following clocks are carried via strip lines to individual modules of the message buffer :

8MHz : 8192-kHz-1:1 clock

4MHz : 4096-kHz1:1 clock

218

SYN 8 : 2-kHz synchronizing pulse (pulse width 122 ns)

SYN 4 : 2-kHz synchronizing pulse (pulse width 244 ns)

(d) Multiplexer

The multiplexer (MUX) is linked via two secondary digital carriers to the switching, network, Messages are exchanged with corresponding LTGs via 63 incoming and 63 outgoing channels on these carriers. As can be seen in Fig. 2, the multiplexer concentrates the data stream of two MBU:LTGs. Every one of the maximum four T/RCs of a MBU:LTG feeds two times eight channels via a 4-Mbit/s highway into the multiplexer. The 63 incoming channels from the switching network of the two digital carriers are distributed by the multiplexer to the four T/RCs of the corresponding MBU:LTG.

(e) Interface adapter

Every MBG is connected with a separate data bus (B:MBG) to the IOP:MB0 and the IOP:MB1. The two IOP cables are junctioned in the MBG and linked to the respective transmitters and receivers. Transmitter outputs and receiver inputs are connected to an internal MBG bus. The interface adapter has the task of converting the IOP:MB push-pull signals to TTL form and vice-versa.

2.2 Interfaces : MBG vs. IOP:MB (CP) / GP (LTG) / SGC (SN) / CCG

(a) Bit-paralled interface between all MBUs of an MBG and the IOP:MB

Every message buffer group (MBG-0 to MBG-3) is linked to the IOP:MB0 or IOP:MB1 with a separate bus system B:MBG (interface A in Fig. 3) :

Message exchange between IOP:MB and MBU is controlled by the IOP:MB and the accessed MBU. Messages are transmitted bidirectionally, in byte-serial and asynchronous form. Asynchronous means that the data bytes are exchanged by means of handshaking procedures. The handshaking procedure is an asynchronous data transfer procedure in byte-serial form and triggered by acknowledgment. Message exchange between IOP:MB and MBU is structured in two parts :

- scanning

- input and output

219

Two IOP:MBs are required per duplicated MBG for complete redundancy (to improve safeguarding). If one of the two IOP:MBs fails, all data exchanges are handled by its partner IOP:MB. In the ultimate configuration for EWSD (i.e. 4 duplicated MBGs for 504 LTGs), 8 IOP:MBs will be required.

Please note : As shown in figure 1, CCNP, CCG & SYP are directly connected to the CP (not via MB), i.e. IOP:MB is the only unit used as buffer to/from the CP for their processors. Hence for each of these three units two IOP:MBs will be required. Hence the requirement of IOP:MBs in an EWSD will be as follows :

Module Name Minium Maximum

IOP : MB for MBGs 2 (For 126 LTGs) 8 (For 504 LTGs)

IOP : MB for CCNP 2 2

IOP : MB for CCG 2 2

IOP : MB for SYP 2 2

(b) MBU interface of an MBG to the CCGAll MBUs obtain their clock pulses from the group clock generator (CG). For the purpose of synchronization with the master clock pulse, the group clock generator selects one of the two central clock generators via a switch-over logic (interface C in Fig. 3). For monitoring and testing, the CG is connected to the first of the maximum of two message buffer units for LTGs of a message buffer group (MBG, interface B in Fig. 3).

220

Figure 4 : MB Interfaces

(c) Bit-serial interface between MBU:LTG and LTGPlease refer to section 2.2 under LTG Architecture also.

Every MBU:LTG is connected to the switching network via two secondary digital carriers (SDC:TSG), one in transmit and one in receive direction (interface D in Fig. 3). Both carriers transmit 128 channel time slots. This corresponds to a bit rate of the 128 X 64 kbit/s = 8 Mbit/s. Of the 128 channels of the SDC:TSG, only 63 (Channel 2,4,6,8….) are used to carry messages to or from 63 LTGs.

In the SDC:LTGs, between LTG and SN, Channel 0 is reserved for the transport of messages.

In the transmission direction LTG—> MBU:LTG, the switching network passes the messages sent by the group processors of the LTGs on channel 0 of the highway SDC:LTG to the MBU:LTG via the channel assigned to a particular LTG on the multiplex highway SDC:TSG.

For example, channel 0 of the SDC:LTG of LTG2 is connected via Nailed-

221

Figure 5 : Message channels in EWSD(Bit-serial interface between LTG and MBU:LTG)

Up connection (NUC) to channel 4 of the SDC:TSG of MBU:LTG.

The effective message exchange between the LTGs and the CP is normally realized in two equal parts via both switching network sides (SN side 0, SN side 1) and via both message (buffer groups (MBG0, MBG1). If a fault occurs in one of the switching network sides message exchange for all LTGs is carried out via the other switching network side. If one MBG fails, the partner MBG handles the complete message exchange.

During system start-up, the semipermanent connections between the MBU:LTG and the LTGs are set by the switch group controls (SGC) in the switching network and remain stable during the entire running time. Since these semipermanent connections are always available, the LTGs and the CP interchange messages without having to burden the processing unit in the CP. In this manner a separate line network for exchange of messages within an exchange is not necessary.

(e) Bit-serial interface between MBU : SGC and SGC

222

The MBU:SGC in a module IOPC can be connected to up to three different switch group controls (SGC) in the switching network via up to three different highways (SDC:SGC, interface E in Fig. 3).

Therefore, up to three different SGCs can be controlled by the MBU:SGC in an IOPC via three different highways. One 64 kbit/s channel pair for both the receive and transmit direction of transmission are used for this purpose on each highway. In the first highway channel pairs number 2 is used, in the second highway channel pair number 4 and in the third highway channel pair number 6.

The MBU:SGC transmits commands it has received and bufferd from the CP via the IOP:MB to the connected SGC via each transmit channel of the three highways.

The MBU:SGC receives messages from the SGCs via the receive channels of the three PCM highways which it buffers and subsequently relays to the CP.

In addition, the MBU:SGC transmits the 8192-kHz exchange clock and the 2-kHz frame mark bit (FMB) in the transmit direction; these are injected by the group clock generator. In the receive direction, the MBU:SGC receives the 64-kHz clock necessary to receive incoming data with a bit speed of 64-kbit/s. Line protocols, the various block types (synchronization block etc.) and data formats are the same as for the MBU:LTG.

2.3 Command And Message Types

Command types

A distinction is made between two main groups of commands :

- transfer commands

- MBU commands

Transfer commands are directed from the CP to the LTGs and SGCs. The MBU:LTG adjusts the data format of the command in accordance with the HDLC transmission method.

MBU commands are directed by the CP to the message buffer control itself and contain tasks relating to monitoring, testing and operation of the MBU. With the exception of RESTART, MBU commands

223

have the same format as transfer commands. They are assigned to the pseudochannel 129 as a difference criterion.

Message Types

A distinction is made between two main groups of messages :

- transfer messages

- MBU messages

Transfer messages are :

messages from the LTGs to theCP (messages),

between LTG and LTG (reports),

between SGC and CP (acknowledgements) and

between LTGs and the CCNC, and vice versa (orders).

MBU messages are generated by the MBU and serve e.g. as error and response messages etc. The format is the same as for transfer messages.

Like MBU commands, MBU messages are identified with the pseudochannel number 129.

2.4 Firmware

The entire control of the message buffer is built up of single controls, which consist of a microprocessor, a program memory and a data memory. The associated firmware is permanently stored in the program memory. It does not, therefore, have to be loaded or initialized by the coordination processor (CP).

2.5 Capacity Stages

The MB(B) is designed to handle the following exchange capacity stages :

- capacity stage for 63 LTGs

- capacity stage for 126 LTGs

- capacity stage for 252 LTGs (Fig. 6)

- capacity stage for 504 LTGs

224

Figure 6 : Capacity stage for 252 LTGs

2.6 Rack And Module Frame Layout

A basic rack and an extension rack is provided (Fig. 7) for the capacity stages of an exchange up to 504 LTG.

The basic rack can contain a duplicated module frame F:MB /CCG(B) (Fig. 8) equipped with central clock generator A (CCG(A)), a duplicated F:MB/CCG(B) without CCG(A) and a module frame for the system panel control and clock distributors external (F:SYPC(A)).

Up to two duplicated F:MB/CCGs without (CCG(A)) can be equipped in an extension rack.

225

Figure 7 ; Rack layout for message buffer

226

Figure 8 : Module frame for MB and CCG (F:MB/CCG(B))

3.0 O&M Aspects (For more details, please refer MMN: MB-IN)

227

3.1 Identification of MBU numbers:

Every MBU is duplicated (EWSD redundancy principle), which means that the entire MB is duplicated, MB-0 and MB-l. This is referred to as having an MBon each side of the system (side 0 or 1).

The MBUs on each of the two MB sides can be divided into two groups viz MBU:LTGs & MBU:SGCs;

MBU:LTGs control the exchange of information between CP & LTG. MBU:SGCs control the exchange between CP and the SGC in the SN.

Each MBU is identified by two parameter values. The following conventions apply for these parameters:

General designation ExampleMBU: LTG-side-no : MBU: LTG-0-4

MBU: SGC-side-no : MBU: SGC-1-O

side : 0 or I = system side to which this MBU is assigned

no : 0...7 for MBU:LTG,

0...3 for MBU:SGC

= consecutive numbering within each system side

Up to three MBUs are combined in an MB gruup (MBG) in an MB frame. The MBUs of an MBG have a shared power suppy and a shared link interface module to the CP.

In normal operation, all MBUs on both system sides are in operating state ACT, with both partners sharing the information traffic load. Partners are always the MBU:LTG-0-X & MBU:LTG-l-X and similarly tne MBU:SGC-0-Y & the MBU:SGC-l-Y. 1f one of the two MBUs fails, the partner on the redundant side handles all traffic. Each of the two MBUs is designed to handle the total load, the load distribution during normal operation merely reprsents optimal utilization of system capacity.

3.2 Reporting MB Faults

228

For the MB there are three possible ways of reporting a detected fault

Fault printout : after internal fault indicators have detected a

malfunction or after the periodic LOOP from CP has detected a malfunction;

• Error message: following a rejected configuration job;

The diagnosis progress message and result message

after diagnosis initiated from the OMT, has found fault in the MB.

For all intetventions in the system it must be noted that the standard system

configuration requires all MBUs to be ACT.

When the exchange is at full capacity, the modules of the individual

MBU:LTGs are each in different module locations (MOLOCs), since one MBU:SGC and.two MBU:LTGs are always present in an MB module frame.

When determining suspect modules, therefore, in the case of a faulty MBU:LTG pay attention to the no. of the MBU:LTG-side-no. The suspect modules are in the fault list uuder the specified fault list number and with the faulty MBU :LTG-side-no.

3.3 Safeguarding and Fault clearance:

Switching off a redundant MBU does not degrade the system, therefore system software usually immediately removes the MBU involved from service by configuring it to UNA when an MBU fault is detected.

The first step in the fault clearance procedure is to configure the faulty MBU to MBL, since it is only in this operating state that fault clearance is permitted.

The last step in every fault clearance procedure, where an MB (or MBU) has been cleared of faults is to return the unit to service by configuring it to ACT.

3.4 Message Buffer : MML Commands for O&M

229

(a) Status Interrogation :Status interrogation of the Message buffer units (MBU:LTG AND MBU:SGC)

230

(b) Configuration:

Configuration of an MBU to MBL status:

Since MBU fault clearance can only be done in MBL. it may be necessary to configure the MBU to MBL as the initial step in fault clearance.

If all MBUs of an entire MBCONF MB: are to be configured simultaneously MB=side, OST=MBL.;

For an MBU:LTGCONE MBUL: MBside, MBUL=no, OST=MBL,

For an MBU:SGCCONF MB US: MB=side, MBUS=r OST=MBL,

Explanation: side = 0 or 1no. = 0 7no. 0 3 (indicates MB-0 or ME-I) = number in case of the

MBU:LTG = number in case of the ~r MBU:SGC

(c) Diagnosis:For an entire MB DIAG MB: MBside, TA =ALL;

For an MBU: LTGDIAG MBUL: MB=side, MBUL=no, TAALL;

For anMBU:SGC DL4G MBUS: !vIB=side, MBUS=no, TA=ALL;

Here ‘TA=ALL’ - => Test of the entire MBU or the MB

(no other parameter is possible here for the MB)

The diagnosis of an entire MB is permissible only if certain requirements are fulfilled. If in doubt, test the MBUs of the MB individually one after the other, always starting with the MBU:SGC.

As soon as the diagnosis has found a fault, the command is repeated with PART, EXECD (partially executed). Following this, a PROGRESS MESSAGE is output containing the entire diagnosis information:

231

DIAGMBUS:

MB=side, MBUS=no, TA=ALL Part Exec’d

Progress Message MMN:MBxxx-zzzz

TEST RESULT BAD TESTED UNIT = MBUS – side- no

FLN=MBUS-y

Error Information:

TEST BLOCK NO = xxxx

Additional Information, H’ zz zz zz zz zz zz zz zz zz zz zz zz

H’ zz zz zz zz zz zz zz zz zz zz zz zz

3.5 TestsOn-line testing for the MB by the operator is not possible.

This is unnecessary, since the test is automaticalty carried out every 20 seconds by the cyclically output LOOP command from the cxchange CP.

3.6 Preventive MaintenancePreventive maintenance in the MB area is not necessary.

Constant monitoring or regular testing of the MB by the operator is not required either.

Message transmission between the MBU:LTG and the LTG functions in handshaking mode, i.e. the command sent form MBL:LTG to LTG must be acknowledged by the LTG.

A periodic MCH test (LTG routine test) is performed by the CP. Every l0s, the CP alternately tests the two message channels assigned to all LTGs in ACT or CBL, for fault-free transmission. It uses test command TECO which is transmitted at 10-s intervals to all LTGs, alternatively via the MCHs in ACT and in STB.

4.0. Exercises ( MB - Functional Structure and Maintenance)

232

Exercise 1Check the current configuration of all MBUs, SN and Message channels

(MCHs).

Exercise 2(i) Locate the cables for (i) MBU:LTG 0-0

(ii) MBU:LTG 1-0

(iii) MBU:SGC 0-0

(iv) MBU:SGC 1-0

(Hint: One end of the cable is from SN.

The other end is at the MB.)

Exercise 3MCH-1 for LTG 0-1 to 0-63 is in UNA status. It means

(a) TS-1 of these LTGs is not accesible.

(b) TS-0 of these LTGs is not accesible.

(c) These LTGs are not accesible.

(d) There could be a problem with SN-I

(e) There could be a problem with MB-0

Exercise 4What will be the status of LTG0-0 to 0-63 in the above case?

Exercise 5Check the side effects in TSG / SSG / MCH / MBU in case of pulling the

cable connecting MBO and TSM 0-0 of TSG 0-0.

( In case of SN - DE4 configuration, e.g. in the NSCBTTC model exchange: )

( Check the side effects in SN / MCH / MBU in case of pulling )

( the cable connecting MBO and TSM 0-0 of SN0. )

Perform all measures to clear the failure.

233

Solutions to Exercises ( MB - Functional Structure & Mice.)

Exercise 1.

STAT MB;

STAT SN;

STAT LTG: LTG = x-x;

Exercise 3. (d)

Exercise 4.It should normally be ACT. (Of course, if the MCH-0 of these LTGs is ACT)

Exercise 5.

STAT SN;

STAT MB;

STAT LTG: LTG=x-x;

After pulling out the said cable,

STAT SN; (Verify that SN plane-0 goes out of service)

STAT MB; (Verify that the MB status remains unaffected)

STAT LTG: LTG=x-x; (Verify that MCH-0 for ‘all’ the LTGs goes into UNA.

Q. Do the MCH-0 go into UNA for all LTGs or only a group

of LTGs?)

After restoring the cable in its original place,

CONF SN: SN=0, OST=MBL;

SN0, OST=STB;

234

Central Clock Generator

What is inside ?

1. Introduction

2. Structure, Functions, Operational Variants

3. Clock distribution in the Exchange

4. Clock Synchronization in Central Clock Generator (A)

5. O & M Aspects

Exercises

235

Central Clock Generator

1.0 Introduction

In order to switch and transmit digital information the sequence of operations must be synchronous throughout the equipment involved. This requires a closk supply with a high level of reliability, precision and consistency for the exchanges in the digital network. In EWSD exchanges, this function is performed by the central clock generator A (CCG (A) Fig. 1.1)

Figure 1.1 : Position of the central clock generator CCG (A) in EWSD

In view of its vital role in the exchange, the CCG (A) is always duplicated. Of the two CCGs [CCG (A) 0 and CCG (A) 1], one is always switched as master and the other as slave. Only master CCG (A)

236

supplies the connected equipment (message buffer (MB), coordination processor (CP) and clock distributors external (CDEX, if provided) with the synchronization clock. The slave CCG, however, controlled by the master CCG, operates in phase synchronism. This ensures that in the event of a malfunction or failure affecting the master CCG, the master slave roles can be switched ove immediately and automatically, and that the clock supply to the connected equipment continues uninterrupted.

Clock distribution within the exchange also proceeds on a master/slave basis, i.e. each equipment unit shown in Fig. 1.1 generates fresh synchronization pulses, which it synchronizes with the output pulses of the equipment preceding it, in order to then synchronise the equipment following it. This ensures that brief interruptions to the clock supply can be safely bridged, the clock generators of the affected equipment units remain free running until the synchronization clock pulse is restored.

The clock pulse generated in each equipment unit sysnchronise the information exchange on three levels within the equipment unit, from one equipment unit to another, and from one exchange to another. The precision and stability of these clock is consistently so high that reference from them are perfectly sufficient for the synchronisation of national networks. For international digital traffic, however, the CCITT has stipulated an even higher level of precision and stability, and the reference frequencies involved here have to be derived directly from atomic frequency standards and fed to the exchanges operating as master (Fig.1.2).

237

Figure : 1.2

2.0 Structure, Functions, Operational Variants

238

2.1 Functions

Synchronous operation :

In synchronous operation (Fig. 2.1) each of the two central clock generators (CCG-0 and CCG-1) comprises three modules :

* module XXA CCGXXA)

* module B (CCGB) and

* module D (CCGD)

Clock generation, synchronization and transfer functions are distributed on modules CCGXXA, CCGB and CCGD as follows :

Module CCGXXA the reference clock (FO1) for module CCGB and synchronizes it to one of the two external reference frequencies (FR) fed in at its input. The clock generated in module CCGB (fO2) is returned to module CCGXXA and with fI1 as reference clock similarly synchronized to the selected fR. The CCG (A) output clock (SYCLK) is thus also synchronized to this reference clock (fR)

With CCG-0 as master and CCG-1 as shlave, further tasks are shared as follows :In the CCG(A) 0, Modules CCGB and CCGD0 amplify the output clock (SYCL0) and transfer it to the following equipment.

- SYCLK0 to the duplicated message buffer MB (B) 0 and MB (B)1.

- SYCLK0 to the coordination processor 113 (CP 113) and

- SYCLK0 to two clock distributors external switche as master (e.g. CDEXO AND CDEX1) if provided.

In the CCG(A)1 modules CCGBI synchronizes the output clock signal (SYCLK 1 ) to the master clock (SYCLSO) supplied by module CCGBO. Clocks are supplied to the connected equipment, howevdr, from the CCG-0 only. The CCG(A)1 runs in phase synchronism, but is blocked on the output side,

239

Figure 2.1 : CCG (A) for synschronous operation

240

Plasiochronous (free – running) operation :

In plesiochronour operation (Fig. 2.2) the CCGs operate without external reference frequencioes (fR). In Figure. 2.2 for example, the CCG(A) 0 is free-running, and module CCGXXA1 symchronizes the reference closk (fO1) to reference clock 4 (R40 traffered from mode CCGXXA0.

Figure : 2.2 : CCG (A) for plesiochronous operations

241

2.2 Operational Variants

Depending on the accuracy required, the following operational variants can be realized :

(a) Synchronous operation with two external reference frequencies (fR) per module CCGXXA, the precision of the CCG output clocks here depending on the tolerance of FR, which is as follows :

- In national synchronous networks with international digital traffic and synchronization of the master exchanges by Cs standards : …fR /fR <10 –11 and

- In national synchronous networks without international digital traffic and synchronization by plesiochronously operated CCGs in the master exchanges : fR / fR< 10 8 to 10 –9

(b) Plesiochronous operation without external reference frequencies (fR) for the master exchanges in national synchrronous networks without international digital traffic, the precisio of the CCG output clocks here depending on the tolerance of oscillator frequency 1 (fO1) generated on module CCGXXA of the master CCG(A) : fO1 / fO1<108 to 10-9;

(c) Plesiochronous operation without external reference frequencies (fR0 and without modules CCGXXA, for island exchanges without digital traffic from and to other exchanges, the precision of the CCG output clocks here depending on the tolerance of oscillator frequency 2 (fO2) generated on module CCGB of the master CCg> fO2/fO2<10-5 to 10-6.

For further details regarding clock genertion, synchronization and transfer byCCG(A), se 4.

242

2.3 Rack and Module Layout

The rack for housing the CCG(A) along with the message buffer (MB (B)), system panel control (SYOC) and clock distributors external (CDEX) of provided, is shown in Fig. 2.3.

The CCG(A) is accommodated at the top of therack in two module frames F:MB/CCG(B) alongwith a message buffer ground Fig. 2.4). The module frame containing the clock distributors external alongwith the system panel control is shown in Fig 2.5.

Figure 2.3 : Rack MB CCG(A), system panel control and clock distributors.

243

Figure 2.4 : Module frame for MB (B) and CCG (F:MB/CCG (B))

Figure 2.5 : Module frame A for System Panel Control and Clock Distributors External, (F:SYPC(A))

244

3.0 Clock distribution in the Exchange

The generation, synchronization and transfer of clocks within the exchange takes place in a number of consecutive stages. The CCG generates the output clock (SYCLK, Fig 3.1) which in synchronous operation, it synchronizes to one of the two external reference frequencies (fR) fed in at its input. The CCG(A), switched as master transfers these output clocks as follows :

- SYCLK to thee two clock generators (CG0 and CGI in the modules CG/MUX-0 and 1) in the duplicated message buffer (MB-0 and MB-1),

- SYCLK to the two clock generators for the realtime clock in the functional units IOP:TA-0 and 1 in the coordination processor (CP1130, and

- SYCLK to the two clock distributors external switched as master (e.g. CDEX0 and CDEX10 if provided.

- The outputs of the CCG(A0 switched as slave are blocked.

The CGs in the MB generate two new output clock signals: the exchange clock (CLK) and the frame mark bit (FMB) which they synchronize to the output clock (SYCLK) supplied by the master CCG(A) and then transfer to the clock generators of the switching network (contained in the functional units LIM in SN and SGCB in SN(B) in the associated switching network side (SN0 or SN1). The assignment MB-0 to SN0 and MB-1 to SN1 is permanent.

The SN clock generators generate exchange clock (CLK) and frame mark bit (FMB) anew, synchronizes them with the CLK/FMB pair supplied, and then transfers them via the associated switching network side (SN0 or SN1)

- to the Group Clock Generators for Line/Trunk Groups (CGSM) in the LTG and

- to the associated clock generator functions (contained in the functional units MUXM) in the common channel signaling network control (CCNC). Of the four MUXM two are assigned to MB-0/SN0 and two to MB-1/SN1, the assignment is permanent.

Both the CGSM and the clock generator functions in the MUXM also generate new output clocks, which they synchronize to one of the two CLK/FMB pairs they receive.

LTGs connected to digital line units (DLU) transfer the output clocks as line clock (LCLK) and line frame signal (LFS), to the associated clock generators (contained in the functional unit BDCG) in the associated digital line unit (DLU). Each DLU contains two BDCGs, each permanently assigned to one of the two associated LTGs.

The CGs in the DLU generate new output clock signals which they synchronize with LCLK/LFS pair supplied.

In a similar fashion the CDEXs switched as master generate new output clocks (ST and MST) which they synchronize to the output clock SYCLK supplied by the master CCG.

245

The IOP:TA synchronizes the associated real-time clock. The CDEX switched as master transfers the ST as control clock to groups of four external (non-EWSD) unit and the MST as master control clock to all slave CDEXs. The CDEX switched as slave generates the control clock (ST) anew, synchronizes it to one of the two master control clock (MST) supplied and transfers it, similarly, to groups of four external equipment units.

The process of clock regeneration and synchronization through several stages is necessary for the following reason:

If the CCG were to supply clocks to all connected equipment units directly (without ontermediate clock generators), a total breakdown of the CCG would lead to an immediate breakdown of the entire clock supply system. The process adopted however bridges any such supply gaps, because the clock generator in each equipment unit, as soon as the clock generator preceeding it fails, continues to run free until the synchronis, of all the clock generators in all connected equipment has been completely restored.

246

Figure 3.1 : Clock distribution in exchanges (example)With CCG(A)0 as master and CCG(A)1 as slave and

Clock Distributors External CDEX0 and CDEX1 244 as master and CDEX2 to CDEX9 as slave CDEXs

The clocks generated by the individual equipment units and transferred to the succeeding equipment unit(s) are uniform for all exchanges and stipulated as follows ;

247

- the synchronization clock (SYCLK) at a rated frequency of 8 kHz(corresponding to a period of 125 us) and a pulse duty ratio of 1:1

- the exchange clock (CLK) at a rated frequency of 8, 192 kHz(corresponding to a period of 122 ns) and a pulse duty ratio of 1:1

- the frame mark bit (FMB) at 2,000 pulses per second with a pulse length of 122ns.

- The line clock (LCLK) for PCM30 multiplex lines at a rated frequency of 2,048 kHz (corresponding to a perod of 488ns)

-- The control clock (ST) at a rated frequency of 2,048 kHz (corresponding to a period of 488 ns) and a pulse duty ratioof 1.1 and

- The master control clock (MST) at a rated frequency of 8 kHz (corresponding to a period of 125 us0 and a pulse duty ratio of 1:1.

4.0 Clock synchronization in Central Clock Generator (A)

There are two inputs available on each of the central clock generators 0 and 1 (two on CCGXXA0 and two on CCGXXA1) for the purpose of feeding in external reference frequencies (fR, Fig. 4.10. The input options (Fig. 1.2) areas follows :

- Analog pilot frequencies via the associated carrier frequency terminating units

Standard values of 300 or 308 kHz

- Digital control clocks via the associated digital interface units,

Standard values of 2,048 kHz (for PCM30) or 1,544 kHz (for PCM24)

- Standard frequencies, for master exchanges, direct from the atomic frequency standard (e.g. Cs standards)

Standard values of 5 or 10 Mhz.

Depending on the CCGXXA switch setting one of the two fRs is used for CCG synchronization. If theused fR fails, the CCGXXA automatically uses the

Other fR for synchronization purposes. If both supplied, fRs fail, the CCG continues to operate in plesiochronous mode.

Various pluggable input modules (IM) are used on the CCGXXA for the connection of the direrent reference frequencies.

248

The selected IMs, corresponding to the fRs connected, are specified by the 2-character code XX in the module designation CCGXXA. The first X corresponds to the first module input, the second X to the second module input. The possible values of X and their meaning are listed below:

- X = 0 for free running (no fR)

- X=1 for fR = 300 kHz and 2,048 kHz,

- X = 2 for fR = 5 MHz and 10 MHz, and

- X = 3 for fR = 308 khz and 1,544 kHz (for PCM24)

For the various possible applications a subset of all XX combinations is defined.

Two test output on theface-plate of module CCGXXA enable the measurement of the levels and frequencies at the output of the Ims. The through-connected fR is indicated by the lit green LED on the face plate of module CCGXXA (REF0 or REF1)

Figure 4.1 : Connection options for the external reference frequencies to the CCG (A)

249

5.0 CCG : O&M Aspects (For more details pl. refer MMN:CCG-IN)

5.1 Special Features of CCG Fault Clearance

(a) There are several different central clock generators (CCG) used in exchanges, to cater for differing requirements in terms of the quality and running characteristics of the oscillators. These must be handled differently during fault clearance.

In order to take all of these CCGs into account, there are a number of decision points in MMN:CCG at which an interrogation of the hardware actually present in the exchange takes place.

The exchange-specific configuration documentation is therefore essential for fault clearance.

(b) When a CCG is configured during fault clearance, clock fluctuations may occur, and these may lead to fault printouts from MB, SN and / or LTG.

For LTG : WITHOUT CONFIGURATION with reference to clock or PLL failure;

For MB : MB INFORMATION with reference to clock or PLL failure;

For SN (in some cases) the fault printout :

SN CONFIGURATION in which an ACT/STB switchover is carried out for the two sides (or units) of the SN.

The above fault printouts may be ignored.

The following fault printouts may also be issued for SN (or units of the SN:TSG and / orSSG):

WITH CONFIGURATION

They have the condeword SN-PLL FAILURE and involve configuration of an SN side (or unit) being configured to UNA.

In this case, the SN-side concerned (or the TSG/SSG concerned) can be restored to service :

250

CONF SN : SN = side, OST = STBM UNCOND = Y;OrCONF TSG : SN = side TSG = no, OST=STB, UNCOND=YOrCONF SSG SN = side, SSG = no, OST = STB, UNCOND = Y

There is no hard fault in the SN.

(C) Of the two CCGs (CCG-0 and CCG-1) CCG-0 has the higher priority

This means :

- If there are different reference frequencies, the ones with the highest priority are always applied to CCG-0

- In plesiochronous mode, CCG-0 synchronizes CCG-1

Under normal operating conditions (i.e no fault or fault clearance ended; no test) the normal configuration :

CCG-0 is ACT/MASTER

CCG-1 is STB/SLAVE

must always be kept or must be established.

5.2 Reporting of CCG Faults

For the CCG there are two principal options for reporting faults at the OMT:

Fault printouts are output when internal fault indicators have detected a malfunction or when the periodic ROUT-TEST or the test following a configuration job has detected a malfunction.

Error messages are output when a configuration job has been rejected

(Exception : in connection with FAILING OF EXT. REF. FREQUENCY the configuration is executed. The fault doesn’t justify taking the CCG out of service, since in most cases the origin of the fault lies outside the reporting CCG.)

If there are no printouts or messages concerning a CCG fault but a fault is suspected, the operating personnel can perform a check of one or both CCGs with c configuration. A configuration is started by entering commands on the OMT.

251

For details of this sequence and for further action to be taken if a fault has been detected see register FC, procedure PR:CCG.

Whenever intervention in the system is necessary, it must be noted that standard configuration means that CCG-0 is ACTg and CCG-1 is STB.

After fault clearance has been completed, the two CCGs must be in these operating states.

5.3 Safeguarding

The two CCGs independently supervise all CCG functions with the aid of internal fault indicators. In particular, this involves constant inservice supervision of the accuracy, stability and level of the frequencies of all clocks entering and leaving the CCG and those used internally.

In addition, the CP as central coordinating unit tests both CCGs, with emphasis on the internal fault indicators, every 24 hours during the low-traffic period (between 4:00 and 4:05 a.m.0 by means of an automatic routine test (ROUT-TEST).

The first part of this test starts with a simulated error, which the CP applies to CCG-0 and CCG-1 in turn. This activates all the internal fault indicators in the CCG; the supervisory circuits respond to this with the corresponding alarm messages, which are then evaluated by the CP. Then all indicators are reset, to restore the original conditions.

In the second part of the test the CP executes a MASTER/SLAVE switchover of the two CCGs. After a given time, allowing any error messages to be output, the original MASTER/SLAVE configuration is restored, thus ending the test.

If the system detects a fault during the ROUT-TEST, it initiates a CCG fault printout, in which all available information on the type of error is summarized. If necessary, it automatically takes the defective CCG out of service.

The defective unit must then be cleared of faults and restored to service by the maintenance personnel. This is done according to the fault clearance procedure named in the fault printout.

Since taking a redundant CCG out of service does not cause system degradation (the CCG in STB is at the same time configured to ACT and takes over the clock supply for the exchange), the system software normally removes the defective CCG from service by configuring it is UNA as soon as a CCG fault is detected.

Exception : In the case of : FAILING OF EXT. REF. FREQUENCY an INFORMATION is output without the CCG concerned being configured.

252

5.4 MML-Command for CCG Maintenance.

STAT CCG (Status of CCG0

DISP CCG (Display contents of CCG fault register)

CONF CCG (Configure CCG)

1. Interrogation of CCG operating state :

STAT CCG :STAT CCG; EXEC’DCCG-0CCG-1ACT STB

If one of the CCGs is in UNA or MBL, enter MMN:CCG at procedure PR:CCG in register FC. This procedure provides the reference to the correct fault clearance procedure for each fault location.

2. Interrogation of CCG Fault Register :

DISP CCG

DISP CCG EXECD

STATUS AND ERROR INFORMATION : CCG-0 CCG-1REF. FREQUENCIES AT CCGXXA : PRESENT PRESENTCCGXXA-MODULE FAULT FREE FAULT FREECCGXXA-PROCESSOR : FAULT FREE FAULT FREECCGB-MODULE : FAULT FREE FAULT FREECCGB-PROCESSOR : FAULT FREE FAULT FREEINTERFACE CCGXXA/CCGB : FAULT FREE FAULT FREECCGB MS-STATUS : MASTER SLAVECCGB CLOCK DISTRIBUTOR : ENABLE ENABLEOPERATIONAL STATUS : ACT STBREFERENCE FREQUENCY 0 : GOOD GOODREFERENCE FREQUENCY 1 : GOOD GOODUSED REFERENCE FREQUENCY : 0 1STATUS FREQUENCY STORAGE : NORMAL NORMALSYNCHRONIZATION STATUS : SYNCHRON 4 SYNCHRON 4

253

3. CONF CCG :

(i) Configuration of CCG to MBL :

A CCG may only undergo fault clearance when it is in MBL.

CONF CCG: CCG = side, OST = MBL;(side = 0 for CCG-0, side = I for CCG-1)

If the redundant CCG is already in MBL or UNA, the following caution will be displayed by the system :

CAUTION: This request may destroy the network synchronism !DO YOU WANT IT TO BE EXECUTED (YES : +/NO: -)<

Apart from special cases, such as during the commissioning of an exchange or in connection with certain types of special fault clearance, this configuration must not be executed. The uniform system clock for this exchange would be lost and would have to be substituted in emergency mode by the invididual group clock generators (mainly in the MBUs). The result would be a flood of alarm messages from the system periphery, referring to clock failures and transmission losses on the PCM links.

So always enter (-). In this case the redundant CCG must undergo fault clearance first.

(ii) Configuration of CCG to ACT/STB:

Configuration to ACT can be done only indirectly for CCGs. If an ACT CCG is configured to another operating state, the system automatically switches the redundant CCG to ACT, assuming that the reundant CCG was previously in STB.

Configuration to STB is of special significance in the case of CCG.

When a CCG is configured from MBL to STB, a general check of CCG functions and safeguarding is triggered. In the CCG, this check replaces the diagnosis and similar functions.

For this reason, configuration to STB is used at the start of fault clearance procedures to verify a fault. In the further course of fault clearance it serves as an indication of whether a fault is still present, has changedor has been eliminated.

CONF CCG : CCG = side, OST = STB;

5.5 Diagnosis

It is not possible for operating personnel to start a CCG diagnosis. The diagnostic functions for CCG ae carried out during configuration from MBL (or UNA) to STB. During this state transition, the first part of the CCG-ROUT-TEST is triggered, which performs a general check of CCG functions and the CCG’s internal fault indicators (Section 5.3, Safeguarding).

254

5.6 Tests

It is not possible for the oparating personnel to perform an on line test of the CCG. This would be superfluous, since a test of this kind is already performed by the CP, with the internal fault indicators, the inservice supervision and the daily ROUT-TEST (Section 5.3, Safeguarding).

5.7 Preventive Maintenance

For a digital CCG(A), preventive maintenance is only necessary for the leading CCG(A) of an exchange operating as network master. It should be carried out every six months (for module CCGXXA Q888) or once a year (for module M: CCGXXA Q1057). This can only be done by a trained specialist with the necessary tools and equipment (synthsizer, atomic frequency standard) and therefore falls into the category of special fault clearance.

6.0 CCG : Functional Structure and Maintenance

Exercise 1

Check the operational status, the mode of synchronization and the current status of the reference frequencies of the CCG. Use for this purpose the STAT/DISP command and the LED of the CCG modules.

Exercise 2.

After checking the fault free operation of both CCG pull off the internal cable which transports the master clock to the slave CCGfor supervision purpose.

Check the status changes inside the CCG by using the concerned MML – command and interpreting the LED OF CCG.

Pull the modules of the UNA-CCG and check the position of the switches concerning the mode of external synchronisation used for the CCG

Perform all measures to reactivate the disturbed CCG

255

System Panel

What is inside ?1. System Panel

2. Structure of the SYP

2.1 SYPD2.2 SYPC

2.3 Rack and Frame layout

3. Operation of the SYPD

4. Alarm Priorities

5. Alarm Mode

6. External Alarms6.1 Assignment of EALs to RM:EA pins6.2 Defining Alarm Texts6.3 Assigning Alarm Texts and defining alarm Priorities6.4 Levels for External DLU Alarms4. Alarm and Archive Files

256

1.0 System Panel and Central System Panel

The function of the system panel (SYP) is to provide audible and visual indications of alarms and advisories from system-internal and system-external supervisory units. Unlike the detailed error messages which can be obtained from the CP at the operation & maintenance terminal if a fault occurs, thesystem panel provides a constant overview of the current functional status of the system.

The functional states of the exchanges in an entire area can be supervised at a higher-ranking OMC. A central system panel (CSYP), which indicates all the alarms and advisoies generated by the switching centers, can be installed in the OMC for this purpose.

Figure 1 : System panel

257

2.0 Structure of the SYP

The system panel (SYP) signals critical alarms, major and minor alarms, advisories and system data coming from the exchange or elsewhere. This signaling may be visual or audible.

The SYP consists of :

a System Panel Control (SYPC), which is housed in the C:MB/CCG rack, and

A maximum of 8 System Panel Displays (SyPDs).

The SYPDs can be located in the exchange, in an O&M centre, or at any other site from which the exchange is to be montored.

2.1 System Panel Display (SYPD)

SYPD displays the data received from and processed by the SYPC. In addition to the 7-segment displays in the header line, there are two groups of displays :

- system displays and

- external alarms.

The system displays are combined in framed functional groups. They are preset as far as their function is concerned. Standard alarm piorities (critical alarm, major alarm, minor alarm) are defined for the system displays. These priorities can be changed within certain limits by means of the command ENTR ALPRIO.

The external alarms are located in the upper right-hand corner of the SYPD front panel. The external alarms can be set as desired. For external exchange alarms, alarm priorities are set by programming in the user EPROM. User-specific alarm texts can be assigned to external alarms.

Advisories can be output as well, e.g. if a functional unit is blocked due to testing or repair work. For output of advisories command is DISP INDIC.

The alarms and advisories are indicated on LED panels with a pair of LEDs and a single LED for each indication, and on three 7-segment decimal displays (for the date, time and call processing CP load).

The alarms are signaled audibly by means of a horn in the housing of the SYPD. A second horn can be connected if necessary via a cable.

258

Alarm Priorities for System Displays

Three alarm priorities can be represented on the SYPD:- Critical alarm, e.g. caused by a functional unit failure with no possibility of switching ove to standby.

- Major alarm, e.g. caused by a functional unit failure with possibility of switching over to standby,

- Minor alarm, e.g. caused by a fault on a PCM link.

2.11 How alarms and advisories are signaled at the SYPD and the OMT

During updating (update key) horn does not sound.

259

If a critical alarm is already set for a unit, a new major or minor alarm which applies to the same unit will be suppressed.

If units are duplicated (e.g. SN ) and SN1), SYPD will not show which of the two units caused the alarm.

The traffic load display is updated every 4 seconds.

Date and time of the CP clock are corrected with an MML command. Subsequently, the SYP clock is automatically synchronized.

The threekeys in the SYP display field serve to operate the SYP,

UPDATE : This key updates all displays on all connected SYPDS. The LED above the update key lights up during the updating process.

TEST : If the test key is pressed, all LEDs should light up and the horn should sound for 800 ms. The horn only sounds if it has not been switched off in the SYPD and if the SYPD dusplays are not currently being updated. The test key only affects the SYPD to which it belongs.

ACEPT : Each new alarm is signaled at the SYPD by the activation of the horn and the fast blinking of the corresponding LED. The alarm must then be accepted by pressing the accept the alarm. This is done by entering the processing codes for a specific alarm in procedure SYP100 with the command SET ALSTAT.

One SYPD, usually the SYPD in themaintenanced center, is a master panel (there can be several master panels). Pressing the ‘accept’ key on a master panel results in acceptance at all other SYPDs. However, presssing the accept key on the SYPD which is not a master panel only affects that SYPD, not any other.

If an alarm is not accepted within 5 minutes, the horn is set to its maximum volume.

How long the horn sounds can be set with the command ENTR ALMODE.

260

2.1.2 SYPD Displays

7-segment displays :

MONTH-DAY DateTIME TimePRCESSOR LOAD Call processing load on the CP

Push Button Keys :

ACCEPT Accept key for SYPDTEST Test key for SYPDUPDATE Update key for SYPD

System displays :

1. EXTERN. EQUIPM (External Equipment) Digital Line Units(DLUs)

2. SERVICE ALARM3. MAINTENANCE ALARM4. LINE TRUNK GROUP5. SWITCHING NETWORK6. COM. CHAN. SIGNALLING7. MESSAGE BUFFER8. CENTRAL UNITS9. CLOCK10. SYSTEM PANEL11. TRUNK GROUP ALARM12. LINE LOCKOUT13. SIGNALLING LINK NO. 714. CALL IDENTIFICATION

23. EXT. DLU ALARM24. ADMIN.ALARMS25. RECOVERY26. TIME INSECURE27. TRUNK GROUP BLOCK28. CAT 1 Catastrophe level 129. CAT 2 Catastrophe level 230. SYTEM OPERATOR

39. HW-UNITS MBL Hardware Units (Indication for HardwareUnits which are in the operating states CBL, MBL or SPLIT)

261

40 SIGNALL LINK NO. 7 BLOCKED41 ALARM INDICATION SUPRESSED

15-22 and 31-38EXTERNAL ALARMS , e.g. Air Conditioning

Dc Power SupplyEntry SupervisionFireMain Power Supply

2.2 SYPC

The SYPC is not duplicated. Like the message buffers (MBs), the SYPC is connected to the input/out processors (IOPs) of the CP. Via this interface (IOP:SYPC), the SYPC receives the necessary data from the CP. The SYPC uses these data to determine what it signals, for example, critical/major/minor alarms, advisories, date, time, and processor load.

A second interface (RM:EA) supplies the SYPC with data on the operating states of external equipment. These operating states can be displayed on the SYPD.

A third interface (TXA : SYPC), allows SYOD signaling to be forwarded to external fault signaling devices.

The SYPC can be installed in either a F:SYPC type or a F:SYPC(A) type frame. In contrast to frame F:SYPC, frame F:SYPC(A) can accommodate 10 CDEX modules in addition to the SYPC modules. The CDEX modules provide the system clock, which controls and synchronizes external devices. Also, instead of the two voltage converters DCCCA and DCCCB, the F:SYPC(A) hbas the voltage converter DCCCR, which supplies the SYPC modules with DC power. If CDEX modules are installed, an additional DCCCL voltage converter must be present which supplies power to the CDEX modules. The standard configuration of an SYPC includes only one T/RM:SYPC module (T/RM:SYPC), which can serve up to four SYPDs (SYPD0 to SYPD3). A second T/RM:SYPC module (T/RM1 SYPC) is only needed when more than four SYPDs are used.

262

2.3 Maximum Configuration of the Frames F:SYPC and F: SYPC (A)

The following table shows the maximum configuration and the appropriate MOLOCs for the modules in the F:SYPC and F:SYPC (A).

263

Figure 2 : Module frame A for system panel control 9F:SYPC(A)

Figure 3 : Rack with system panel control.

264

Figure 4 : Structure of the system panel

3.0 Operation of the SYP

3.1 Notes on Operation

Signaling at the SYPD serves to inform operating personnel of alarms or advisories. After a new alarm occurs, the horn must be switched off by pressing the accept key on the SYPD.

Each alarm is the basis for a fault clearance action. With the help of the LED designation of the new alarm, the general fault clearance procedure SYP100 must be used to begin fault clearance. In this fault clearance procedure, the new alarm must be accepted by entering a processing code. When this is done, the LED will flash only half as fast. Subsequent to procedure SYP100, fault clearance continues with appropriate maintenance manual. The unit which caused the alarm is placed back in service by executing this procedure in its entirety; and only then will alarm display at the SYPD be canceled.

During the SP100 fault clearance procedure, fault listings which corrspond to the signaling at the SYPD are selected from the alarm file. This is done with the comands.

265

DISP ALARM andSRCH ALARM

When using these commands, the term OBJECT occurs as a parameter. This parameter directly names the unit signaled at the SYPD. The following table shows which abbreviations must take the place of OBJECT in order to match SYPD or OMT signaling.

Object table

Lable on SYPD OBJECT LED numberAdmin Alarms ADMINAL 24Com. Chan. Signaling CCS 6Clock CLOCK 9Central Units CU 8Extern. Equipm. DLU 1 and 4Ext. DLU Alarm EALDLU 23External Alarms EALEXCH 15-22, 31-38Line Lockout LNLCKOUT 12Line/Trunk Groups LTG 4Maintenance Alarm MAL 3Message Buffer MB 7Recover RECOV 25Service Alarm SAL 2Signaling Link No. 7 SIGLING13Switching Network SN SN 5System Operator SYOP 30System Panel SYP SYP 10Trunk Group Alarm TGAL 11Time Insecure TIMINSEC 26

266

3.2 Configuration of SYP

STAT SYPCONF SYP

Operating States of the SYP

Three operating states are defined for the SYP; these operating states indicate the following :

ACT : The SYPC is functioning properly.The SYPD may or may not be fault-free.Faulty SYPDs do not influence the operating state of the SYP.The SYP continues to be in the ACT state.

Failure of one SYPD is signaled at the remaining SYPDs.

UNA : The SYP is either defective or has been taken out of service manually.

MBL : The SYP is out of service due to testing or maintenance.

Permissible state transitions for SYP :Old\new ACT UNA MBLACT - yes yesUNA yes - yesMBL yes - -

3.3 Safeguarding

Of all possible faults, most are detected in the SYP are itself by :

Routine test programs in the SYPC and the SYPDs

Safeguarded data transmission between CP/SYPC and SYPC/SYPD

Validity checks in theSYPC

Routine polling of SYPC by the CP

If an error is detected in an SYPD, the processor in the SYPD is stopped and the interface to the SYPC is blocked. A SYP alarm is displayed at the affected SYPD and the processor load display is blacked out.

A failed SYPD is detected by the SYPC and reported to the CP. Also, an alarm is signaled in theSYP display field of the remaining SYPDs. If four SYPDs fail within the specified time period, the CP takes the SYPC out of service.

267

After a failed SYPD has been repaired, the SYPC automatically returns it to service and reports this to the CP.

SYPC errors are detected by an internal routine test and reported to the CP in the form of spontaneous error messages. This displayed as an SYP failure at the SYPDs.

The interface between CP and SYPC plays a special role. The transmission of “processor load” is timed in the SYPC. If this transmission does not take place within a predefined time, then STP failure and total failure of the processor are signaled. If transmission resumes, this alarm is automatically canceled.

The CP issues test commands in short intervals to test SYPC operation.

All error messes lead to initiation of SYP fault analysis (FA:SYP) FA;SYP distinguishes among errors which lead to SYPC total failure and thus to total failure of the SYP area (unconditional power –off), errors which do not terminate operation (e.g. SYPD failure), and errors which only cause an SYPC reset.

4.0 Alarm Priorities

The standard alarm priorities are provided in the system. This assignment of the three alarm priorities critical alarm, major alarm and minor alarm is permanently set in normal service and can only be changed during the installation phase. Alarm priority can be changed with ENTR ALPRIO.

Display Alarm Priorities.

All alarm priorities set in the system for alarm signaling on the SYPD can be displayed with the command DISP ALPRIO. The display is dependent on the alarm unit. Only the LED EXTERN. EQUIPM is not displayed, as this LED does not indicate an alarm priority, but only the supplementary information, that the LTG alarm signaled is a DLU alarm.

In response to the command DISP ALPRIO: ALUNIT = xxxxxxxx; only those alarm priorities are output which belong to the alarm unit specified. In response to the command DISP ALPRIO; (without any parameter) a complete list of all alarm units together with their respective alarm priorities is output.

DISP ALPRIO :ALUNIT – xxxxxxxxALARM PRIORITIESALUNIT SDG ALPRIOxxxxxxxx xxxx xxxxxxxx

Explanation :ALPRIO : Alarm priority CRITICAL critical alarm

MAJOR major alarmMINOR minor alarm

268

SDG (Service Degradation) NO No degradation of service is possible for thealarm unit specified in ALUNIT.

YES Degradation of service is possible for the alarmunit specified in ALUNIT i.e on the failure of both alarm units, the CRITICAL ALARM priority is signaled instead of that specified in ALPRIO.

ALUNIT (Alarm unit) For the parameter ALUNIT the following values are allowed:AIC air circulatorANNAL announcement trunk alarmBAP base processorBCMY bus to common memoryBDCG bus distribute and clock for DLUCALLID1 MCI immediateCALLID2 MCI on subscriber requestCALLID3 MCI over trunkCAP call processorCCG control clock generatorCCNP common channel signaling network controlCCSL common channel signaling linkCH channelCMY common memoryCR code receiverCSC central service channelCUK central unit kernelDCC direct current conveterDIU digital interface unitDIUMAL DIU maintenance alarmDIUSAL DIU service alarmDLUC digital line unit controlEALDLU external DLU alarmEALEXCH external exchange alarmEMSP emergency service equiment for push-button subscribed DLUHSP high speed printerHSFC high speed printer controlIOC input output controlIOPCDD IOP for cartridge disk devieIOPMB IOP for message bufferIOPMDD IOP for magnetic disk deviceIOPMTD IOP for magnetic tape deviceIOPSCD IOP for serial data communication devices.IOPSCDV IOP for serial data communication devices vIOPSCDX IOP for serial data communication devices xIOPTAIOP IOP for tape disk devic

269

IPC interprocessor channelISUB subscriber ISDNLTg line trunk groupLTGCED line trunk group centralLTGPAF line trunk group partialMB message bufferMBUL MESSAGE BUFFER UNIT FOR ltgMBUS message buffer units for LTGMBUS message buffer unit for SGCMDD magnetic disk deviceMDDC magnectic disk device controlMTD magnetic tape deviceMTDC magnetic tape device controlMU processing unitRAE recorded announcement equjipmentRHMG ringing gemeratpr amd metering voltage generator for DLUSILT signaling link terminalSILTC signaling link terminal controlSLM subscriber line moduleSN switching networkSSG space stage groupSUB subscriber analogSYP system panelSYSOP call for system operatorTGAL trunk group alarmTIMINSEC time insecureTSG time stage groupTu test unit

5.0 Alarm Mode

The alarm mode for the SYP consists of the two service features STATUS and HLIM. For the service feature STATUS, three different alarm statuses can be defined in the user SPROM in the SYPC: ALSTAT 0, ALSTAT 1 and ALSTAT2.

Enter Alarm Mode

Using the command ENTR ALMODE, the SYP can be brought into one of the three alarm statuses alstat-0, alstat-1 or ALSTAT-2 and the service feature HLIM can be switched on or off.

ENTR AL MODE. (Enter alarm mode)

STATUS = xxxxxxxx Alarm status

HLIM = xxx Hooter alarm limit (YES / NO)

270

Service feature HLIM :

If an alarm is not confimed on the SYPD within 5 minutes, the audible signal is set to maximum volume.

If HLIM=NO is then entered for this service feature, this characteristic is retained.

If, however, HLIM – YES is entered, the audible signal is switched off automatically after the time programmed in the user EPROM (audible signal time can be programmed between 1 and 255 seconds in 1 second steps). At the same time,the flashing frequency is halved, i.e the alarm is thereby changed from the unconfirmed form to the confirmed form.

After each new start of the SYP, the audible signal time limit is switched off. It is only switched on again in a subsequent update procedure, or if entered by MML command.

Service feature STATUS :

The following values are allowed for the STATUS parameter :

ALSTAT 0, ALSTAT 1, ALSTAT 2

ALASTAT 0 : Output of alarms to external fault signaling devices via module TXA:SYPC is blocked;

Other characteristics as for ALSTAT 1.

ALSTAT 1 : This status determines- which SYPDs are master displays.

- which alarms are forwarded via module TXA:SYPC to external fault signaling devices.

- Whether, in the event of an alarm being forwarded via module TXA:SYPC, a continuous alarm is output on a master display, with or without cancellation on confirmation,

- Or whether a pulsed alarm with a specific pulse duration is formwarded via module TXA:SYUPC.

ALSTAT 2: The same options are available in this status as in status 1, although different combinaions are allocated for status 2 than for status 1, enabling a switchover from status 1 to status 2, e.g. a daytime / night-time switchover.

After every new start, the SYPC is in alarm status 1. Only in theevent of a subsequent “updating procedure” is a change of alarm statuscarried out, if necessary by means of an MMl Command.

Display Alarm Mode

The current alarm mode of the SYP can be displayed at any time with the command DISP ALMODE.

271

DISP AL MODE :ALARM MODE ;STATUS HLIMxxxxxxxx xxxxxxxx

the values for parameters HLIM and STATUS are the same as those described above.

Figure 5 : External Alarm Line (site = exchange)

4.1 Alarm Texts for External Exchange and DLU Alarms and Alarm Priorities for External DLU Alarms

In the EWSD system, fault printouts are generated for all faults occurring in system equipment and are stored in alarm files. Apart from information identifying the system equipment affected, each fault printout also contains a code word, which is a short text describing in greater detail the fault which has occurred.

The SYP gives the suer the option of displaying not only alarms and indications of system equipment, but also from equipment outside the exchange (external alarm units). For this purpose, a maximum of 16 LEDs or pairs of LEDs are provided on the SYPD in the EXTERNAL ALARMS panel. In addition, up to 16 external alarm units can be connected to each DLU. The external DLU alarms are indicated by the Ext. DLU ALARM pair of LEDs. Users can create fault printouts containing relevant information for each of these external alarms, which they have defined themselves, by entering fault-specific texts in the system. These texts can also be checked, canceled and assigned to external alarm

272

lines (EAL). For the external DLU alrms, the levels on theindividual EALs can be set by means of an MML command. These commands are described on the following pages.

The external alarm units of an exchange are routed directly (or via an MDF) to the SYPc (module RM:EA). The exact description of how the external alarm units are connected can be found in section LED:SYP of register TAB in the Maintenance Manual MMN:SYP.

EDL No. Pin No. EDL No. Pin No.(EAL No.)1 3 13 432 4 14 443 5 15 454 6 16 465 7 17 476 8 18 487 9 19 498 10 20 509 11 21 5110 12 22 5211 13 23 5312 14 24 54

Assignment of Individual External Alarm Lines (EAL) to the Pins of the Module RM:EA

The external alarm units of a DLU are connected via DLU module ALEX. The exact description of how these external alarm units are connected can be found in section LED;DLU of register TAB in maintenance Manual MMN:DLU.

4.2 Enter Alarm Text

The ENTR ALTEXT command can be used to enter a text of up to30 characters which may have any structure, but must not be empty. This command is also used to assign a text number to the text which has been entered. If a text already exists in the system under the number entered, this text is overwritten. A maximum of 40 different texts may be entered.

The command DISP ALTEXT provides an overview of which alarm texts already exist in the system and which text numbers are assigned to them.

ENTR AL TEXT: (Enter alarm text)

TEXTNO = xx Text number (1 to 400

TEXT = “ xxxxxxxxxxxxxxxxxxxxxx”; Alarm text which represents an external alarm in a fault listing. This text must be no longer than 30 characters and must be enclosed in quotation marks.

273

Cancel Alarm TextTo cancel an alarm text, identified by its text number :

CAN AL TEXT : TEXTNO = xx;

The cancellation is performed only if the alarm text in question is no longer assigned to an external alarm line (EAL).

Display Alarm Text

For displaying a single alarm text, identified by its text number, or all alarm texts :

DISP AL TEXT: TEXTNO = xx;

TEXTNO TEXT

xx xxxxxxxxxxxxxxxxxxxxxx … xxx

If the parameter TEXTNO is specified, the alarm text stored under that number is displayed and if no text exists in the system under that number, an empty text is displayed .

If the parameter TEXTNO is not specified, then all alarm texts in the system are displayed with their text numbers. Text numbers to which no alarm text is assigned are not displayed.

4.3 Assign Alarm Text and Define Alarm Priority for DLU

Each external alarm unit is connected via its own external alarm line (EAL). In order that the correct alarm text is displayed on the OMY or the VDU for an alarm which has occurred externally, an assignment of EAL to alarm text must be created by means of the MML command CR EAL.

CR EAL : (Create external alarm line)

SITE = xxx, Hardware Installation Site.

SITE = EXCH if the EAL in question is connected to an exchange.

SOTE = DLU, if, however, the EAL is connectedto a DLU.

If the value EXCH is entered for this parameter, the priority is not specified as it must already be specified in the user EPROM.

EAL = xx, External alarm line 1 to 24 for SITE = EXCH1 to 16 for SITE = DLU

TEXTNO = xx Text number 1 to 40

274

ALPRIO = xxxxxxx; Priority of external DLU alarm. The required priority of the external DLU alarm is entered in this parameter only in cases where SITE = DLU. Possible values are :

CITICAL = critical alarm

MAJOR =major alarm

MINOR = minor alarm

Cancel Alarm Text Assignment

An existing assignment of an alarm text to an external Alarm Line (EAL) can be canceled by :

CANEAL SITE = xxx, Hardware installation siteSITE = EXCH if the EAL in question is connected to an exchange.SITE = DLU, if,. However, the EAL is connected to a DLU.EAL = xx; External alarm line 1 to 24 for EXCH1 to 16 for DLU

Figure 6 : Overview of Administration of External Alarm Lines and Texts.

Display Alarm Text Assisgnment

275

The assignments existing in the system between the alarm texts and the individual EALs can be displayed on the OMT Using the command.

DISP EAL: SITE = EXCH or DLUEAL = xx ;

Depending on whether the value EXCH or DLU is specified for parameter SITE, different masks are displayed in response to this command. The parameter EAL may also be omitted, in which case all alarm textsexisting in the system ardisplayed with reference to the specified hardware installation site.

6.4 Levels of External DLU Alarms

The user can determine, bymeans of an MML command, which voltage level on the relevant EAL should be evaluated as “no alarm” for external DLU alarms; These levels, determined by an MML command, can then be displayed individually or collectively on the OMT.

Creation of Levels for External DLU Alarms

The command CR EAL LVL can be used to determine which level on each individual EAL is to be evaluted as “ no alarm" for each DLU.

CR EAL LVL : (Create external alarm line level)

DLU = xxxx, The number of the relevant DLU is specified (possible range of values: 10 – 2550)

EAL = xx, External alarm line (1 to 16)

LVL = xxxx; This parameter specifies which level is to be evaluated as “no alarm” on the corresponsding EAL.

HIGH : Either a level on the EAL which deviates from 0 or the open EAL is interpreted as “no alarm present”.

LOW : Ground potential on the EAL is interpreted as “no alarm present”.

Display Levels for External DLU Alarms

The command DISP EALLVL is used to display the level which is to be evaluated as ‘no alarm present’ for one specific EAL or for all EALs.

DISP EAL LVL : (Display EAL level)

DLU = xxxx, The number of the relevant DLU is specified (range of values : 10 to 2550)

276

EAL = xx; External alarm line (1 to 16)

DISP EAL LVL: DLU = xxxx, EAL = xx;

DLU EAL Non-Alarm Level

IGH (Example)

7.0 Alarm and Archive Files Important for O&M Staf

7.1 HF ARCHIVE System Archive File

- stores all maintenance messages of the system

- contains also additional information which is required for special fault clearance by the system specialist e.g. recovery messages, audit messages.

HR. ALARM is a duplicated cyclic file.

To read the contents of any ARCHIVE file :

DISP AENTRY ; AFILE =[ AENTRY =]

[TOC = ]

SEL AENTRY : AFILE +[TIME = ][DATE = ],MSG =[ALPRIO = ];[DIR = ]!

Remark : Additional ARCHIVE files can be created with CR A FILE. They can be used for customer specific message routing.

7.2 AM. ALARMAlarm File

- contains all fault messages which belong to no yet cleared SYPD alarms - can only be read by the operator with the command DISP/SRCH ALAR- is a duplicated System File automatically created by the system.

To read the contents of AM. ALARM file :DISP ALARM : [OBJECT = ]

[ALSTAT = ][ALPRIO = ];

SRCH ALARM : [OBJECT = ][ALSTAT = ]

277

[ALPRIO = ][MSGNO = ]

Bharat Sanchar Nigam Limited

EWSDSYSTEMS ARCHITECTURE

278

NETAJI SUBHASH CHANDRA BOSE TELECOM TRAINING CENTREKALYANI, NADIA, WEST BENGAL, PIN – 741235

279