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INTRODUCTION
Today, BSNL is the No. 1 telecommunication company and the largest public sector undertaking of
India and its responsibilities includes improvement of the already impeccable quality of telecom
services, expansion of telecom services in all villages and instilling confidence among its customers.
Apart from vast network expansions, especial emphasis has given for introducing latest technologies
and new services like I-NET, INTERNET, ISDN (INTEGRATED SERVICES DIGITAL NETWORK), IN
(INTELLIGENT NETWORK), CDMA, GSM and WLL (WIRELESS IN LOCAL LOOP), BROADBAND, 3G services
etc. Now BSNL has also entered in mobile communication. BSNL has all the new services send
technological advantages, which are available with any well, developed Telecom network anywhere
else in the country. Full credit for all above achievement goes to the officers and staff of the BSNL. The
administration is fully aware of the challenges lying ahead and quite committed to provide the latest
and best telecom services by their continued support and active co-operation.
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Company Profile
Bharat Sanchar Nigam Limited (BSNL) is India's leading
telecommunications provider and the country's largest public-sector firm.
BSNL provides local-exchange access and domestic long-distance services
through a network of more than 45million access lines covering most of India. It
also offers wireless communications, data and Internet services, as wellas business voice and data services. The company is still
controlled by the government, as is one of India's other large
phone companies, Mahanagar Telephone Nigam Limited (MTNL). Plans to
merge the two companies have been discussed but seem to be on
hold.
HIGHLIGHTS
Bharat Sanchar Nigam Limited has a vast reservoir of highly skilled and Experienced work force of about 3, 57,000personnel.
We believe that our staff, which is one of the best trained manpower in the telecom sector, is our biggest
asset.
To meet the technological challenges, employees are trained for technology up-gradation,
modernization, computerization etc in BSNL's training Centers spread across Country.
To apex training centers of BSNL i.e. Arera Telephone Exchange Center (ATX) at Bhopal is
comparable to any world class Telecom Training Center. Moreover, 43 zonal training centers and a
National Academy of Telecom Finance and Management have been running for several years now.
Different curriculums run in these centers to impart technology based training, Training for
Attitudinal change, basic educational and skill development Program etc.
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CONTENTS
Acknowledgement
Preface
Certificate Company Profile Introduction Structure and about the exchanges
1. Computer unit
2. Power plant
3. AC Plant (CENTRAL AIR CONDITIONER)
4. MDF (MAIN DISTRIBUTION FRAME)
C o n n e c t i n g S y s t e m
E W S D E x c h a n g eGeneral overview
Introduction of EWSDFunctional block diagram of EWSD
General features
Positional structures
Capacity stages
Functional unit of SN
Switching network
Rack assignment
Module frame layout
Interconnections of switching module
FunctionsO&M aspects
Exercises
Switching techniques
Internet Call record data(CRD) Leased circuit Conclusion Glossary of terms and abbreviations
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STRUCTURE AND ABOUT THE EXCHANGES
All telephone subscribers are served by automatic exchanges, which perform the functions the human
operator. The number being dialed is stored and then passed to the exchanges central computer,
which in turns operates the switching to complete the call or routes it a higher level switch for further
processing. Todays automatic exchanges uses a pair of computers, one running the program that
provides services and the second monitoring the operation of the first, ready to takeover in a few
seconds in the event of equipment failure.
Various exchanges present in BSNL are:
C-DOT
E-10B
OCB283 (Exchange & TAX)
EWSD (Exchange & TAX)
All exchange has some purposes and some basic structural units, which are:
1.Subscribers connection unit
2. Switching network (CX)
3. Control unit
4. OMC (Operational & maintenance Control)
Structure of the exchange
For smooth working of an exchange following unit are very important: -
1. Computer Unit: - it deals with additional services of the exchange to the customers with the help of
computers.
2. Power Plant:- to feed proper power supply to exchange
3. AC Plant: - to maintain the continuous temperature + or 2 degree Celsius to the digital switch
(exchange).4. MDF: - to connect switch (exchange) with the external environment (subscriber) i.e. it is the
interface between subscribers and exchange.
CONNECTING SYSTEM
Exchange Side Line Side
EXCHANGE MDF CABINETS PILLARS
DISTRIBUTIONSUBSCRIBERS
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Computer unit: -
As the name specified it is the main part of the exchange that deals with the all services provided by
the exchange to the customers with the help of computer. It also provides the updated data to all
other part of the exchange. The customers are using the services of the exchange by using the internet
also gets connected to the main server present this room via an internet room. It mainly consists of the
servers that are providing the different services. The main servers of this room are:-IVRS is used for the change
number services provided by the exchange.CERS are provided by the exchange to avoid the problems that the users are
facing the repairing of telephone. In this system when the user enters its complained it gets directly
entered to the server and user is allotted with an id number. LOCAL DIRECTORY ENQUIRY is another services
provided by the exchange, by using this; subscribers calls the particular number and gets the directory enquiry. The server
present in the main computer room provides this service. INTERNET DIRECTORY ENQUIRY is the latest service by the
exchange. In this type of service makes it enquiry using the internet, which gets connected to the main
server at the internet room in the exchange and further to the main server in the computer room.2.
POWERPLANT: -
As we know that, the power is the main source or any organization. It isthe case of E-10B exchange.
That is the first requirement of any organization isthe input. The main source of this exchange is ACsupply. However, as soon as the powersupply is gone off, then what is source? No one think on this
that the telephone is always plays its role in the human life. Even if the power supply gone off. Thus
there must be adjustment source of power. The main parts of the power room are:
i.Batt eries: - these are t he instant sources of th e power as soon as power is gone off.
ii.Cha rging - Di schargi ng Un it: - t he b atter ies we are using in t hepower room need timely
charging. As soon as the AC power supplyis on, we make use of the charging unit present in the power
room. The slowly charging of the batteries is known as the tricklecharging. But sometimes we need the
BOOSTER charging. In thistype of charging awe take of the batteries from the load and chargeseparately,
until it gets fully charged. The main work of the discharging unit is to control the dischargingof the
batteries.iii.Inverter and Converter Unit: - the main use of this system is tochange AC mains to DC and vice versa
as required by the parts of exchange.
iv.Engine Room:-we know that the batteries are the instant source of supply but we cannot use it for
much larger time, thus for this, we have an engine to generate the power supply. They are of 885
KVA. Thus, this room controls the supply of the engine.
UPS OPERATING MODES:
UPS system has three operating mode which can be designated as
1. Normal mode
2. Emergency mode
3. Recovery mode
I . N O R M A L M O D E :
The rectifier charger draws power from the ac mains & converts it into DC. This DC power is supplied to
the inverter which converts it back into AC power to feed the critical load connected to the output of
the inverter.
Inverter and Converter Unit: - the main use of this system is to change AC mains to DC and vice versa
as required by the parts of exchange.
Engine Room:-we know that the batteries are the instant source of supply but we cannot use it for
much larger time, thus for this, we have an engine to generate the power supply. They are of 885 KVA.
Thus, this room controls the supply of the engine.
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CENTRAL AIR CONDITIONER
For the function of electrical equipment, cooling system is basic requirement. The basic advantages of
cooling systems are following-
It provides the thermal stability so that the temperature does not reach the tolerance limit of
electronic equipment
It saves equipment from dust so to avoid malfunction ofequipments.
It protects equipment from excess humidity which can caused rusting of equipment.
The basic unit of measurement used in the industry is known as ton of refrigeration (TR) which is
equivalent to the heat extracted in 24 hours for converting thousands kg of liquid to ice at zero degree.
The compressor is the heart of the AC system and the costliest. It increases the pressure and
temperature of the refrigerant gas coming from the evaporator coils by compressing it.
Compressor comes in various types. The most widely used is simple reciprocal type a cylinder and
piston arrangement. For capacity more than 120 TR, centrifugal compressors are used. The condenser
liquefies the refrigerant gas by a heat exchange process. The capillary tube or the expansion valve
pressurizes liquid refrigerant and meters it flows to the evaporator.
The refrigerant then passes through the evaporator coils, which extract heat out of the ambience.
MAIN DISTRIBUTION FRAME
The primary function of MDF is:
The fault of telephone number is removed in the MDF; it is called as Fault Remove Section.
For removing the fault of telephone number, we use the testing
These testing are T.T.Y. testing, Group testing, etc.
For any type of testing firstly we need the vertical no. or the live tester, printer and computer test N.E.
number of that particular telephone number.
The telephone numbers are also disconnected in the MDF because of some specific reason.
ORGANISATION OF THE MDF
PARTS OF THE MDF
Horizontal side
Vertical side
HORIZONTAL SIDE:
It is again subdivided in to two parts
Exchange side
Line side
Description of the horizontal side:-
RACK: - On the rack, the tags are situated. One rack is having eight tags. The courting is done from up
(0) to down (7).
TAG: - Each rack consists of eight tags.
1 tag = 4 core
1 core = 4 bunch
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1 bunch = 2 line
N.E.:- The word NE stands for the NUMBER OF EQUIPMENT.
It is a 128 pair cable. The EWSD and MDF connected by NE.
WEDGE:-If we want to disconnect any two numbers then we insert a wedge between subscriber side
and exchange side. Here wedge works as insulator made of plastic.
VERTICAL SIDE:
The vertical aside connected to the underground cable. This cable is having 100 pairs.
These pair is distributed when we allot the telephone number to the subscriber.
Vertical side is again subdivided in two parts:
One part is connected with the horizontal side and another with the subscriber line by using 100 pair
underground cable.
This is how the present day telephone system works. Different exchanges have different architectures
of switching call routing and other features.
Now let us see how BSNL has kept up with the changing world and provided the subscribers with thelatest facilities technologies, which include the V-SAT network, Internet, the WLL (wireless in local
loop) and the GSM mobile.
EWSD
EWSD and Office Switch
1. General OverviewEWSD (Elektronisches Whlsystem Digital in German, Electronic Digital Switching System/Electronic
World Switch Digital in English) is one of the most widely installed telephone exchange systems in the
world. EWSD can work as a local or tandem switch or combined local/tandem, and for landline or
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mobile phones. It is manufactured by Siemens AG, who claims that EWSD switches perform switching
for over 160 million subscriber lines in more than 100 countries.
DeTeWe bought its first EWSD under license in 1985 for remote switching. Bosch built its first EWSD as
a local exchange in 1986. Deutsche Telekom, formerly Deutsche Bundespost, the largest German
telephone company, uses EWSD and System 12 (Alcatel), the former more than the latter.
In 2007, Nokia Corporation and Siemens AG formed the new company Nokia Siemens Networks, and
responsibility of further development and shipments of the EWSD system is dependent on this new
company.
Contents
1 Hardware
2 Software
3 Technical data
Hardware
Main subsystems are:
CP (Central Processor)
MB (Message Buffer)
CCNC (Common Channel Network Control)
LINE (Analog Line Group) LTG (Line Trunk Group)
DLU (Digital Line Unit)
SN (Switching Network)
All system units are redundant so the inactive side can take over immediately in case of an error.
DLU handles analog and ISDN lines and includes codecs for analog lines, one of the BORSCHT functions
for subscriber lines. Digital signals are assigned a time slot. DLU concentrates traffic onto a Line B unit,
as well as Primary ISDN and V5.2 connections. Supervision and address signaling (dial pulse, DTMF) are
also integrated in the DLU. For PCM-30 (E-1) connections to other exchanges, Line C Units are used,
which also handle signaling including SS7, MFC R2 signaling, IKZ (dial pulse), and E&M.
he Switching Network consists of 4 space division stages of 16x16 switches, and a time division sectionwith 16 stages of 4x4 switches. Control is provided by the CP Co-ordination Processor.
There are the following kinds of Co-ordination Processors:
CP103 with max 22,000 call attempts in the busy hour
CP112 with max 60,000 call attempts in the busy hour
CP113D with max one million call attempts in the busy hour
CP113C with max six million call attempts in the busy hour
CP113E with max ten million call attempts in the busy hour
Software
The software of EWSD is called APS (Automatic Program System). The APS is on a hard drive and
includes the operating system, developed by Siemens in cooperation with Bosch. It is predominantly
written in the CHILL language. Application software is switch specific and serves among other things
traffic management, path search, and call charging. Support software serves translating programs,
binding modules as well as administration of libraries for generating data. Operating and data
communication software serve for co-operation of maintenance centers and switching centers.
Technical data
Number of access lines: to 250,000
Number of feeder lines: 240,000
Traffic connection: 25,200
Call attempts in busy hour: 10 million
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Operating voltages: -48V -60V -90V
Rate zones: 127, for each zone of 6 tariffs
Tariff change-over at 15 minute intervals
Space requirement with 10,000 access lines: 35 square meters
15-25 *C Temperature
2. INTROCDUCTION OF EWSDSwitching 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 up to 63 LTGs is called
SN DE4. For larger exchanges SN DE5.1 is used which can connect up to 126 LTGs. Similarly SN DE5.2
can connect up to 252 and SN DE5.4 up to 504 LTGs.
DLU LTG(B)
LTG(C)
CCNC
MB
CCGSYP
OMT PRINTER
CP
MTUMDD
SN
Figure 1. Position of Switching Network in EWSD
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3. BLOCK DIAGRAM OF EWSDEWSD switching system structure chart
DLUDigital line unit
SLM(A,D,X,I) -
subscriber line modules
DLUC - Digital line unit
controller
LTGLine trunk group
SNSwitching network
SSNC Signaling system network
control
CCNC Common channel network
control
MBMessage buffer
CPCoordinating processor
BAP - base processor
CAP - call processor
CMY - common
memory
IOC- I/O controller
AMP - ATM bridge
processor
B:CMY0(1) - commonmemory access bus
CCGCentral clock generator
Net
Manager
Network management system
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4. GENERAL FEATURESSwitching network is provided in capacity stages SN: 63LTG to SN: 504LTG, i.e. up to 63 LTGs can be
connected or, via other intermediate capacity stages, up to 504 LTGs can be connected. The modularly
expandable SN has negligibly small internal blocking and can be 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 networks 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-connections make up a 64 Kbit/s connection path.
All of the switching networks internal highways have a bit rate of 8192 bits/s (Secondary Digital
Carriers, SDCs). 128 time slots with a transmission capacity of 64 Kbits/s each (128x64 = 8192 Kbits/s)
are available on each 8192 Kbits/s highway. Separate cables each containing several (eight or sixteen)such internal highways, are used for each transmission direction. All externally connected highways
also have the same uniform bit rate.
The switching network combines the numerous switching network functions in a few module types.
These modules work at very high through-connection bit rates; 8192 Kbits/s and some even at 32768
Kbit/s. For example 1024 connections can be switched simultaneously through a space stage with 16
inputs and 16 outputs. Although these highly integrated 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 orders.
5. Position and Functional StructureSwitching 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 exchangewith 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 Buffer Unit (MBU) are identified as follows as shown
in figure 2.
* SDC: LTG interface between SN and LTG: time slot 0 for message exchange between the
LTG and coordination processor (CP) as well as between two LTGs, time slot 1 to 127 for
subscriber connections.
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* SDC: CCNC interface between the SN and the common channel signaling network (CCNC):
for common channel signaling.
* SDC: TSG interface between SN and a message 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
connections.
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.
LTG 1
LTG n
CCNC
CP
MBU
MBU
MBU
SPACE
STAGE
GROUP
OF
SN:DE5
TIME
STAGE
GROUP
OF
SN:DE 5
OR
SN:DE4
SGC
SGC
Figure 2: SN Internal and External Interfaces
SDC:LTG
SDC:LTG
SDC:CCNC
SDC:TS
SDC:SG
SDC:SG
SN
MB
SDC:SSG
SDC:SSG
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TABLE 1: SN Capacity Stages
Capacity stages of
switching network
SN:63LTG
(DE 4)
SN:126LTG
(DE 5.1)
SN:252LTG
(DE 5.2)
SN:504LTG
(DE 5.4)
Switchable
traffic(E)
3150 6300 12600 25200
Local Exchanges
No. of lines 30000 60000 125000 250000
Transit Exchanges
No. of trunks
7500 15000 30000 60000
Structure TST TSSST TSSST TSSST
Connectable no. of
LTGs or
LTG+CCNC
63
or
62+1
126
or
125+1
252
or
251+1
504
or
503+1
6. Capacity StagesThe present version of SN is available in capacity stages SN:63LTG, SN:126LTG, SN:252LTG and
SN:504LTG. Modular structure permits partially equipped SN. Up gradation from DE5.1 to DE5.2 and
from DE5.2 to DE5.4 is possible with the help of supplier. SN DE4 is not upgradable to DE5.1 as TSG and
SSG are not separately identified in SN DE4. The traffic handling capacity, connect ability for various
capacity stages of SN are shown in Table 1.
7. Functional Units of SN7.1 Switching path
The switching network is subdivided into time stage groups (TSG) and space stage groups (SSG). Due to
its modular structure, the EWSD switching network can be partially equipped as needed and expanded
step by step. The switching network uses the following switching stages:
one time stage incoming (TSI)
three space stages (SS) and
One time stage outgoing (TSO).
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These time and space stages (functional units), shown in figure 3, are 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 (SSM16|16)The switching network capacity stage SN:63LTG, 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.
LTG
MBU:SGC
SN1
SN0
LIL TSM SSM 16|16
TSO
SSG1.0
LTG
MBU: SGC
TSG1.0
TSG0.0
LIL TSM
LIS
TS0
MBU: SGC
SSG0.0
LIS SSM 8|15
SSM16|16
SSM
15|8
Figure 3: The seven module types in SN: DE5
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7.1.1 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 exchanges
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 is connected on the interface to SSG and has 8 inputs
and 8 outputs.
7.1.2. 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 locations 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.
7.1.3. 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 retain
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 periods. 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.
LIL
0
SSM16|16 or LIS
0
TSM
Figure 5 : Time stage
module TSM
LIL
0
TSO
0
SSM16|16 or LIS
3
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SDC: LTG
0
1
2
3
4
5
6
7
56
57
58
59
60
61
62
63
01
2
3
0
1
2
3
0
1
2
3
0
1
2
3
01
2
3
TSMB-00
1
2
3
0
1
2
3
TSMB-70
1
2
3
0
12
3
0
1
2
3
0
1
14
15
0
1
14
15
0
10
2
3
14
15
0
1
2
3
0
1
14
15
TSGx-x
Fig. Time Stage group internal
connections
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INTERNET
Introduction:
The Internet is not a program, not software, not hardware or a big system. It is a group of various co-
operating computers worldwide interconnected by computer based on TCP\IP communication
protocols. People use it to get information over a standard communication link. The hundreds or
thousands or millions of computer network are connected to each other for exchanging the
information which is based on the unique identity and set of procedures. Internet is a series of
interconnected networks providing global link to information.
GIAS: BSNL launched the Gateway Internet Access Service (GAIS) through dial up/leased/ISDN network.
Users can access GAIS from 99 cities in India by this means.
INTERNET TECHNOLOGY
The basic function of Internet can be summarized as under-
Interconnecting of computers to form a network.
Interconnecting of computers to form a network of networks.
To establish a communication link between two computers within as network.
To provide alternate communication link among the networks, even if one network is not working.
These are based on TCP/IP communications protocol.
Transfer of a file through Internet:-Suppose a file is to be transmitted on Internet from one computer to other ones
Break the file in to small packets
Attached destination and source address in o packets
Multiplexed and transmit these packets
At destination de-multiplex the packets
Remove address bits from the packets and assemble the data in to the original file
Make source bits as destination address and send the acknowledgement in to the source
Therefore, it is clear that network hardware sends the packets to specified destination and network
software reassembles of communications, the computer network performs the following functions-
Addressing and routing
Fragmentation and error correction
Data error checking
Connectivity control
Multiplexing and de-multiplexing
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Data flow control
End users interface etc.
The data handling
A single module cannot handle the entire process. One that adopted as a standard is an open system
interconnection (OSI) model.
COMMON TERMINOLOGY USED IN INTERNET:
WWW:
World Wide Web (WWW) is a wide area hypermedia information retrieval aiming to give universal
access to a large universe of documents.
HTTP:
Hyper text transmission Protocol (HTTP) is the communication protocol used to transfer documents
from the server to client over the WWW (http:// www).
HTML:
Hyper Text Markup Language (HTML) is a system of marking or tagging the various parts of web
documents to tell the browser software how to display the document text, link graphics and link
media.
ISDN:
Integrated Service Digital Network (ISDN) is a digital phone connection technology that provides both
voice and data services over the same connection.
ISP:
Internet Service Provider (ISP) is an agency that provides Internet access and other net related services.
NATIONAL INTERNET BACKBONE (NIB)
Networking is a key component of any Internet Services Provider (ISP) operations. The networkingequipments like access servers, routers and modems are critical to the successful functioning of ISP.
An ISP node where subscribers enter internet, consists of a set of equipments as given below.
Access server
Router
Modem bank
LAN (Local Area Network) components
Security server
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Rack, console & power supply
Network management agent.
Help desk
Call Detail Record (CRD)
A call detail record (CDR), also known as call data record, is a data record produced by a telephone
exchange or other telecommunications equipment documenting the details of a phone call that passed
through the facility or device. It is the automated equivalent of the paper toll tickets that were written
and timed by operators for long-distance calls in a manual telephone exchange.
Contents
A CDR is composed of fields that describe the exchange. Examples of fields include:
* the number making the call (calling party)
* the number receiving the call (called party)
* when the call started (date and time)
* how long the call was (duration)
* the phone number charged for the call
* the identifier of the telephone exchange writing the record
* a sequence number identifying the record
* additional digits on the called number used to route or charge the call
* the result of the call (whether it was answered, busy etc)
* the route by which the call entered the exchange* the route by which the call left the exchange
* call type (voice, SMS, etc)
* any fault condition encountered
Each exchange manufacturer decides which information is emitted on the tickets and how it is
formatted. Examples:
* Send the timestamp of the end of call instead of duration
* Voice-only machines may not send call type
* Some small PBX does not send the calling party
* to make all the records correct
Production
CDRs are produced by the charging system of the telephone exchanges. In Nortel exchanges and in
other North American exchanges, the charging system is called Automatic Message Accounting. In an
Alcatel OCB switch, the charging system is software known as TX.
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TransportComputer networks are used for transporting CDRs to a central point for processing, with X.25 links
being widely used worldwide for transporting CDRs. The CDRs of calls still in progress are held by the
sending exchange until the call is completed.
ProcessingCall accounting or call logging software is generally used for retrieving and process CDRs. This system
can be called a business support system (BSS). In the billing system the price of the call will becalculated.
Besides for billing, CDRs can be used for supporting the operations of the telephone company by
providing information on faulty calls, and measures of the amount of traffic taken along particular
routes.
Station messaging detail record
A station messaging detail record (SMDR) is similar to a CDR, but the most important difference is in
the usage. CDRs are for telephone company use, and may carry information about the processing of a
call. To create actual billable call records, it may be necessary to correlate several CDRs. CDRs may also
have a role in internal financial transfers among phone companies
Major Account Billing Exchange Logistical record or MABEL, is a vehicle for the exchange of majoraccount billing data between carriers. The records cover all of the billing elements of a major account,
including summary billing information and call detail-level information.
A wireless service provider or a company that acts as a liaison to a wireless service provider uses
MABEL. Also defined in MABEL is a Major Account Consolidator, which can be the wireless service
provider or third party that acts as a liaison to the corporate entity. MABEL
SMDR, in contrast, is intended for end-user organization, and as a way to understand their telephone
usage and billing.
Leased Line
To transmit data between computer and electronic information devices, BSNL provides data
communication services to its subscribers. It offers a choice of high, medium and low speed leaseddata circuits as well as dial-up lines. Bandwidth is available on demand in most of the cities. Managed
leased Line Network (MLLN) offers flexibility of providing circuits with speeds of n x 64 Kbps up to 2
Mbps. Useful for internet leased lines and international principle Leased Lines (IPLCs).
For dedicated point to point speech, private wire, tele-printer and data circuits are given on lease basis.
Leased circuits are provided to subscribers for internal communication between their offices/factories
at various sites within a city/town or different cities/town on point to point basis, or on a network basis
interconnecting the various sites.
Managed Leased Line Service(MLLN): The MLLN is a Managed Leased Line Network system which is
proposed to provide Leased line connectivity. The State-of-the-art technology equipment MLLN isdesigned mainly for having effective control, monitor on the leased line so that the down time is very
much minimized services .
Speech Circuits (Hot Line or Private Wire) - Local or Long distance circuits within two locations in a city
or between two different cities provided for the same applicant. The Terminating equipment at both
ends is telephone without dialing facility. Both way signaling and speech is possible.
Data Circuits - Local or Long distance data circuits at different speeds viz. nx64 kbps and 2 mbps. Data
Circuits are of different types:
Point to Point Data Circuits - Local and Long Distance
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Private Data Network - More than one Local or Long Distance leased circuits converging on a location
such that data from one leased circuit can be transferred automatically to another leased circuit for the
same subscriber.
Closed User Group - Leased circuits can be used by more than one legal entity if they form closed user
group. The following categories of user groups constitute closed user groups for the purpose of
licensing Private Telecom Networks.
1. Producer of goods and his whole -sale traders /agents.
2. Provider of service (not being a telecommunication service) and his whole-sale traders/agents.
3. Producers of same categories of goods.
4. Providers of the same category of service.
5. Holding company and its subsidiaries.
6. Interconnected undertakings.
7. Companies under the same management
8. Travel agents issuing tickets on the member airlines, whose network they use including the
network of a group of member airlines.
9. Computerized Reservations System (CRS) service providers owned by airlines.
10. Shared networks of banks for use of Automatic Teller Machines (ATMs), Electronic Points of
Sale(EPOS)/credit authorization terminals.
11. Financial institutions registered primarily to deal in securities and their agents/dealers.12. Financial institutions registered as Mutual funds and their agents.
13. Financial institutions which are registered as depositories and their agents/dealers.
14. Other non-banking financial institutions.
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CONCLUSION
Hence in the last I can say that taking training in such an organization proved to be very beneficial for
me. I learnt quite a lot about electronic exchange, Internet, Land line, WLL, Mobile GSM & 3G, and the
basis of processing Exchange. I also got firsthand knowledge of how a Telephone Exchange works.
The first phase of training has proved to be quite fruitful. It provides an opportunity to encounter with
such huge machines.
The architecture of company has various units. They are linked and working of whole plant is
controlled make the student realized that engineering is not just learning the structure description and
working of various machines. But the greater part is planning proper management.
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GLOSSARY OF TERMS AND ABBREVIATIONS
ADM Add/Drop Multiplexers
ANALOGUE An electrical signal which is analogous
to changing physical quantity measured
BSC Base Station Controller
BTS Base Tran receiver Station
C-DOT Centre for Development of Telemetric
CD Cabinet Cable Distribution Cabinet
CDMA Code Division Multiple Access
CKM Cable conductor kilometer cable
sheath kilometers multiplied by the
number of conductor pairs in each cable
CLIP Calling Line Identification Processing
COAXIAL CABLE A cable with a single wire in the centre
of cylindrical conductor forming a pair
of carrying electrical signals
CT BOXES Cable Termination Boxes
DECT Digital Enhanced Cordless
Telecommunications
DEL Direct exchange lines, one each for
every telephone connection
DIGITAL EXCHANGE The exchange having signals coded into
binary pulses and having little or nomoving parts
DIU DECT interface unit
DLC Digital Loop Carrier
DWDM Dense Wavelength Multiplexing
Terminal
EDX Electronic Data Exchange
EPABX Electronic Private Automatic Branch
Exchange
ETRP Electronic Trunk Relay PlatesEWSD TAX Electronic Wheeler System of Digital
Trunk Automatic Exchange
GHz Giga Hertz
GSM Global System for Mobile
Communications
HDPE High density polyethylene
HDSL High bit rate Digital Subscriber Line
Hertz or Hz Frequency (cycles per second), named
after Heinrich Hertz - usually in ranges
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of kilo 1000 - KHz, mega 1,000,000 -
MHz or giga 1,000,000,000 - GHz
IDR Intermediate Data Rate
ISDN Integrated Services Digital Network
LDST Long Distance Satellite Telephone
LOI Letter of Intent
MARR Multi Access Rural RadioMBM Multi Base Module
Mbps Mega bits per second denoting digital
frequency
MCPC Multi Channel Per Carrier
MDF Main Distribution Frame
MUX Multiplex
NIT Notice Inviting Tender
NE Lines Non Exchange Lines
OFC Optical Fiber Cable
Optical Fiber (OF) Glass fibers using light waves for
transmission of signals
OLA Optical Line Amplifiers
OYT Own your telephone
PABX Private Automatic Branch exchange
PBX Private branch exchange
PCM Pulse Code Modulation
PCO Public Call Offices
PDH Plesiochronous Digital Hierarchy
PERT Chart Programmed Evaluation Review
Technique Chart
PIJF Cable Polyethylene Insulated Jelly Filled Cable
PSPDN Packet Switch Public Data Network
PST Progressive Stock Taking
PSTN Public Switched Telephone Network
PVC Polyvinyl chloride
PW Private Wires
RLU Remote Line Unit
RSU Remote Switching Unit
SACFA Standing Advisory Committee on Radio
Frequency Allocation
SDH Synchronous Digital Hierarchy
SMPS Switch Mode Power Supply
SRCs Subscriber Record Cards
SSAs Secondary Switching Areas
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STD Subscriber trunk dialing
STM Synchronous Transport Module
TAX Trunk automatic exchange
TDMA Time Division Multiple Access A
transmission technique used in digital
radio transmission in which the use of a
frequency is divided into time slots that
are shared amongst several users.
TELEX TelePrompTer exchange
TTH Triangular Tubular Hybrid
UHF Ultra high frequency (300 to 3000 MHz)
VHF Very high frequency
VPT Village Public Telephones
VSAT Very small aperture terminal
WLL Wireless-in-Local Loop
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