DOCUMENT RESUME

ED 431 300 EF 005 394

AUTHOR Haworth-Roberts, A., Ed.TITLE Crime Prevention in Schools: Specification, Installation,

and Maintenance of Intruder Alarm Systems. Building Bulletin69.

INSTITUTION Department for Education and Employment, London (England).Architects and Building Branch.

ISBN ISBN-0-11-270677-0PUB DATE 1989-00-00NOTE 93p.AVAILABLE FROM HMSO Publications Centre, P.O. Box 276, London, SW8 5DT

England; Tel: 0171-873-9090; Fax: 0171-873-8200 (7.50British pounds).

PUB TYPE Guides - Non-Classroom (055)EDRS PRICE MF01/PC04 Plus Postage.DESCRIPTORS *Alarm Systems; *Crime Prevention; Educational Facilities;

Elementary Secondary Education; Foreign Countries;Guidelines; *School Security

IDENTIFIERS England

ABSTRACT

Greater use of expensive equipment by schools has alsoincreased the potential for vandalism and theft, giving an increased role tointruder alarm systems. This document provides guidance on the management andtechnical aspects of forming policies for installing and operating intruderalarm systems in educational buildings. Also provided are examples of goodpractice based on case studies. Appendices, comprising the bulk of thedocument, contain technical details of intruder alarm systems, includingdetection devices, auxiliary equipment, wire-free intruder alarm systems andportable alarms, intruder alarm system control panels, local audible andremote signaling alarms, and central monitoring stations. A glossary is alsoprovided. (GR)

********************************************************************************* Reproductions supplied by EDRS are the best that can be made ** from the original document. *

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Building Bulletin 69

U.S. DEPARTMENT OF EDUCATIONOffice of Educational Research and Improvement

EDUCATIONAL RESOURCES INFORMATIONCENTER (ERIC)

1)(This document has been reproduced asreceived from the person or organizationoriginating it.

0 Minor changes have been made toimprove reproduction quality.

Points of view or opinions stated in thisdocument do not necessarily representofficial OERI position or policy.

Department of Education and Science

PERMISSION TO REPRODUCE ANDDISSEMINATE THIS MATERIAL HAS

BEEN GRANTED BY

John Birch

TO THE EDUCATIONAL RESOURCESINFORMATION CENTER (ERIC)

1

w S S Iift

/

Crime Prevention in Schools:specification, installation and maintenance of

intruder alarm systems

Department of Education and Science

Building Bulletin 69

London: Her Majesty's Stationery Office

3

© Crown copyright 1989First published 1989ISBN 0 11 270677 0

11

FOREWORD

In recent years there has been a considerableI increase in the use of expensive equipment suchas micro computers and video recorders in ourschools. This has made many schools moresusceptible to incidents of break-ins and thef t.Intruder alarm systems have an important role toplay in preventing crimes of this nature in schools.This Building Bulletin offers practical advice onthe selection, installation and use of intruderalarm systems. The bulletin complements the otherinitiatives I am taking in cooperation with localeducation authorities, teachers and governors tomake our schools more secure.

JLcuiJohn Butcher MPParliamentary Under-Secretary of State

t.

Contents

1 Introduction

2 Intruder alarm systemseffectiveness

typical system

3 A planned approach

planning policy

installation policy

maintenance policy

monitoring policy

4 Design of intruder alarm systems

technical aspects

installation

commissioning

Page

1

2

2

5

6

6

7

9

10

12

5 Maintenance of intruder alarm systems 13

6 Operation of intruder alarm systems

setting of alarm system controls 15

user induced false alarms 15

7 Case studies

1 A large middle school in the Midlands 17

2 A small Victorian first and middle

school in London

3 A large comprehensive school

incorporating a continuing education

centre in Southern England 19

4 CDT centre at a North of England school 20

Page

Appendix 1 Intruder detection devicesultrasonic 'volumetric' detectors

microwave 'volumetric' detectors

passive infrared detectors

dual technology detectors

self-monitoring detectors

pressure mats

protective switches

continuous wiring

foil on glass

breaking glass detectors

vibration detectors

protection of safes and cabinets

sound detectors

beam interruption detectors

some types of specialist and less used forms

of intruder detection

Appendix 2 Auxiliary equipment

Appendix 3

Appendix 4

18 Appendix 5

Appendix 6

Glossary

Wire-free intruder alarmsystems and portablealarms

Intruder alarm systemcontrol panels

Alarm signalling localaudible alarms and remotesignalling

23

29

32

46

47

47

50

53

54

56

59

61

61

62

65

67

70

72

77

Central monitoringstations 82

85

v

Acknowledgements

Research was carried out by the Architects andBuilding Branch of the Department of Educationand Science. The Department would like to thankthe LEAs that gave access to their schools anddetails of their experience of installing andmanaging intruder alarm systems. Thanks are alsodue to SCEME (Society of Chief Electrical andMechanical Engineers), Crime Prevention Centreand Home Office for their very useful commentsand observations during production of thisbulletin. Technical literature and comment wereprovided by many companies in the securityindustry and the Department is grateful for thisvery valuable support to our research.

The project team members were:

Superintending Architect:Principal Engineer:

Senior Engineer:

Editor:

Graphics Designer:

vi

A J BrantonM J PatelR M HeardA Haworth-RobertsH Omar

EWroduct.ozl,

1. The incidence of theft and vandalism inschools, has steadily increased during the lastdecade. In England, during 1985, crimes of thisnature amounted to losses of approximately £30million. In human terms there can be a very seriousimpact upon the morale of pupils, teachers andparents.

2. Schools are particularly vulnerable since they aregenerally open to wide sections of the community,have elevations hidden from public view andincreasingly contain valuable electronic equipment.Expensive portable items like computers,televisions, videos, tape recorders, keyboards etc,are easily stolen and disposed of.

3. Coordinated with other security measuresintruder alarms can be cost effective in combattingcrime in schools. Local Education Authorities(LEAs) have employed intruder alarms with varyingdegrees of success in terms of technical effectivenessand value for money. Typically, LEAs commencedby installing a few systems on an ad-hoc basis andmany now embark upon major capital programmesto install alarms in many educational buildings.

4. LEAs have evolved their own policies for theinstallation, maintenance and management ofintruder alarm systems. As the number of systemsincreases and technology advances, there is a needfor LEAs to consider their policies, and makechanges where advantages can be identified. Thepurpose of this Bulletin is to provide guidance onthe management and technical aspects of formingpolicies for installing and operating intruder alarmsystems in educational buildings. Part 7 showsexamples of good practice based upon case studies.Appendices 1-6 contain the technical details ofintruder alarm systems.

a

2 Int der alum systems

5. Schools can be subject to a variety of differentacts of vandalism and break-ins. BB 67' suggeststhat measures like:

clear management policy

111 prompt repairs

involvement of local community

can all help in reducing the number of break-ins.

6. However, there will always be some schools inany LEA where in spite of the above actions thebreak-ins and thefts will persist. In such cases theinstallation of an intruder alarm system may be theonly answer. Intruder alarm systems, if correctlyinstalled and used, can be highly effective incombating crime. Table 1 shows the effect ofinstalling intruder alarm systems in 15 schools inan LEA in the North of England. As indicatedthere were 119 break-ins in the 15 schools for theyear preceding the installation of an intruder alarmsystem. After two years the annual number ofbreak-ins had reduced to 13.

7. In 1986 school buildings in Great Britainsuffered fire damage in excess of £30m. Fire alarmand detection systems can clearly help to reduce thisloss. However, in the absence of an automatic firedetection system, there is considerable benefit inhaving a well designed intruder alarm system, as itcan activate an alarm in response to the effects of afire. Also since arsonists are often intruders as well,the alarm system may either deter an arsonist oractivate an alarm before a fire has been started.2

DES Building Bulletin No 67 Crime Prevention in Schools PracticalGuidance, published in 1987. Details various preventative measuresagainst vandalism, theft and arson in schools.

2 DES is currently preparing separate guidance on technical aspects offirelarm systems. Tooics to be covered include fire detectors, systemdesign, operation and communication links.

TABLE 1.

Effectiveness

8. Intruder alarm systems if they are to operatesatisfactorily must be:

ag correctly designed

al properly installed

u sensibly used

regularly maintained

9. If any of the above actions is neglected thesystem will be prone to false alarms or, worse stillfail to operate at a critical time. False alarms whichrequire call-outs can prove to be very expensive.Some of the earlier systems were particularlysusceptible to false alarms, which resulted in loss ofcredibility of intruder alarm systems generally.However, a modern system based on micro-processor controls, central monitoring and improveddetection technology can offer an excellentprotection to any school. The appendices to thispublication detail the technical considerationsinvolved in selecting equipment and communicationservices.

Typical system

10. A typical school intruder alarm system willconsist of movement detectors, a control panel andan audible alarm. In most cases a telephone line isused to automatically convey the alarm signal to theemergency telephone operator or alternatively to aprivate monitoring station so that the police can bealerted. In response, it is normal for the police toissue a radio message to despatch a patrol car to thescene of the alarm. Figure 1 illustrates a typicalintruder alarm system and communication network.

History of break-ins at 15 north of England schools

No. of break-ins in the yearbefore the installation of an

intruder alarm system.

No. of break-ins after intruderalarm system installation.

1stYear

2ndYear

119 43 13

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11

11. The large range of detectors includes devicesthat sense movement within the volume of spaceand more simple devices that sense opening doors orfoot pressure. These days electronic movementdetectors are the most widely used form of intruderdetection. The passive infrared movement detectoris fixed to a wall or ceiling and aimed into thespace under protection. When an intruder moves inthe space a change occurs in the infrared radiationreceived by the detector resulting in an alarm signalbeing sent to the control panel. Ultrasonic detectorsuse high frequency sound to detect movement byresponding to changes in reflected sound wavescaused by human movement. Similarly, microwavedetectors use radio waves to sense movement. Thedetectors are connected to a control panel by cablessimilar to that used for telephone installations.

12. Modern control panels contain a good deal ofcomplex electronic circuitry but are designed to beuser-friendly, and may be simply operated by thelayman. They can be used to switch 'on' and 'off'the entire system or selected parts of the system.Under normal circumstances an intruder alarmsystem is never switched off. When in 'off' mode itwill still raise a local alarm if the system equipmentor wiring is tampered with.

13. Many of the alarm companies and some LEAsoperate central monitoring stations. Using atelephone line and a digital dialler connected to thealarm control panel the monitoring station isinformed of alarm conditions. Most often themonitoring service extends to logging all eventssuch as opening and closing times and may evenadvise the personal ID code used by the personoperating the control panel. Although centralmonitoring imposes greater revenue costs it isgradually superseding the "999" automatic diallerand is generally preferred by most local policeforces, who regard intruder alarm systems connectedto central monitoring services as being morereliable, and less prone to false alarms.

14. Recently radio-operated alarms of reasonablequality have been developed. They may be useful inbuildings where special problems impedeconventional wiring such as the presence ofasbestos. However they have a limited applicationparticularly in large buildings.

15. Portable alarms consist of a single unitcombining a detector, controls and audible alarm.They may be useful as a temporary measure to scareoff the casual intruder but are unreliable and tendto become damaged or stolen by the moreexperienced intruder.

16. An intruder alarm system will only operatecorrectly if each component performs reliably.

4

Hence, only components of good quality should beused. The temptation to use low-priced, poorquality materials should be resisted. In extremecases selection of inadequate components can lead tointruders passing undetected, high levels of falsealarms and associated resetting charges.

17. Apart from ensuring quality of installation,LEAs also need policies which will achieveconsistent designs, maintenance standardisation, andadequate user procedures. Many LEAs have realisedthe advantages of specifying an approved list ofcomponents, thus tenders from installing companiescan be evaluated on a more equal basis. Similarlysuch standardisation holds maintenance advantages.Unless LEAs have a planned approach they can endup with different types of systems and highmaintenance and resetting charges.

12

3 A :c3azamed appxonth

18. The design of an intruder alarm system mustmeet the requirements of the particular school andits problems.

19. There is very great value in looking athistorical data. Records of break-ins, theft and arsonattempts with the monetary value of loss can bevital in directing the application of finite resourcesinto new alarm installations. Of similar importanceis the need for continuing monitoring to quantifythe benefit of installed intruder alarms. This helpsto evaluate the effectiveness of different types ofintruder alarm systems and components. Analysiscan enhance the quality of future policies for designand installation. Geographical trends are anotherrelevant factor. One way to determine whether anintruder alarm system should be installed or not isto carry out a Risk Assessment Audit. BuildingBulletin 67 deals with Risk Assessmentmethodology in detail. Schools that are identified asabove average risk should be given high priority forthe installation of an intruder alarm system.Analysis may reveal that protecting one high risksite simply changes another nearby low risk siteinto a high risk site. Hence, in some situations itmay be decided, with foresight, to simultaneouslyprotect all relevant premises that lie within closeproximity of each other.

20. To evaluate design and monitor the schemes'effectiveness LEAs should set up liaison groups onintruder alarm systems. This group may typicallycomprise representatives from the EducationDepartment, Treasurer's Department, PropertyServices, LEA's insurance company and the localpolice force. A typical example is in the north ofEngland, where the LEAs of Durham County,Cleveland and Northumberland have coordinatedtheir efforts to form the North East RegionalSchools Security Group and have benefited from aunited approach against crime in schools. Cheshirehas done much on risk management that has alsoproved useful to other authorities. Commonproblems exist throughout the country and localsecurity liaison groups may gainfully establishcommunication links between themselves. Re-inventing the wheel is to no one's benefit.

?laming policy

21. This seCtion deals with the many technical andadministrative functions that need to be takenaccount of by LEAs in determining a policy for

installing and owning intruder alarm systems. Asowners of multiple alarm installations, LEAs needto develop policies that will enable them to movewith the times and achieve cost effectiveness.

22. In 1988 it typically cost approximately£1,000 and £3,000 to install a basic intruder alarmsystem in a primary and secondary schoolrespectively. For an average school the maintenancecosts, excluding call-outs and repairs, may typicallybe £150 per year whilst central station monitoringcould cost a further £75. Clearly intruder alarmsystems are expensive to install and maintain. LEAsshould undertake a rolling programme ofinstallations in schools with high instances of break-ins.

23. It is important that LEAs are not constrainedeither technically or contractually from obtainingcompetitively priced intruder alarm services. This isachievable by building into their policy: freedom ofchoice for determining purveyors of installations;maintenance service, and central station monitoring.Essentially the policy must formalise the process forintruder alarm installation, maintenance andmonitoring. The LEA's own administrative functionof intruder alarm management should be an integralpart of an overall policy.

24. The LEA's administration must be tailored totheir policies for designing, installing, maintaining,and monitoring alarm systems. Cost control is mostvital. The nature of intruder alarms can producenumerous invoices in respect of engineers' visits toreset or repair alarm systems. Often, the work iscarried out in response to an automatic alarm signaland the owner of the alarm system has littleopportunity to control or supervise the work.Invoice sums may be relatively small but thecumulative effect can be very substantial. Thetemptation to "routinely- authorise such smallinvoices for payment should be resisted. Manual orcomputerised data analysis should be used tohighlight the number of invoices and accumulativemonetary value relative to any alarm system.Anomalies can therefore be investigated resulting inappropriate remedial action. Detailed costassessment can reflect upon the quality of alarminstallations and servicing. Comparisons may bemade between different installers and servicingorganisations. In some cases changes in the patternof building use or staff can be identified as a reasonfor cost fluctuations.

13

5

25. It is reasonably straightforward to budget fdrrecurring charges for maintenance and monitoring.Similarly, a budget can be established to fund arolling programme of new installations andadditions to existing installations.

Installation policy

26. The competitive tendering of new installationworks or the modification to existing systems will,by definition, ensure value for money. However, itis essential to seek tenders against a full clientspecification. Failure to specify contractual andtechnical standards invites competing companies toproduce the lowest quotation based upon their owncontract conditions and minimal technicalstandards. Only full specification ensures thattenders can be assessed on a fully comparative basis.Similarly, close supervision may be necessary toensure compliance with specification.

27. Production of a list of standardised selectedcomponents and installation methods and use ofappropriate contract conditions will enable existinginstallations to be extended by open competition.This is a vital consideration, since most basicinstallations will require extending, often to a valueof work exceeding the original installation cost. Itwould therefore be commercially inappropriate to becontractually tied to the original installers ofindividual alarm installations. The policy forowning and operating intruder alarm systems, mayadvantageously facilitate options for the future,permitting any selected private contractor orsuitably trained direct labour work force toimplement adaptations to any individualinstallation.

28. Many LEAs have benefited from beingcommitted to a standard specification. Good qualitycomponents installed to a high standard make for areliable installation. Inferior standards produceunacceptable levels of false alarms and are not costeffective. A short list of "standard" control panelsaids user familiarity and further reduces falsealarms. This also offers adavantages of futurecompetitive tendering of maintenance andmonitoring service.

Maintenance policy

29. Technically, as a minimum, the routinestandard of maintenance should satisfy therequirements of BS 4737 Section 4.2. Owners ofmultiple alarm installations have a wide scope informulating a policy for maintenance. Scope shouldexist within the policy to employ any selected

6

private contractor or trained direct labour force toperform routine or call-out service on any intruderalarm installation.

30. LEAs often invite tenders for various buildingservices maintenance contracts. These servicesinclude heating, ventilation, air conditioning,electrical services, lifts, communication systems andfire alarms. There is no valid reason why intruderalarm maintenance should be excluded fromcompetitive tendering. Typically the building stockcould be divided into a number of groups with adifferent group being put out to tender each year,under a three year contract. Some proprietarysystems, such as sound monitoring, can necessitatea tied maintenance agreement with the owners ofthe proprietary system. However, in all normalintruder alarm installations the specification ofstandard components and installation methodsshould offer complete flexibility for maintenancearrangements. As with other building services thereis a commercial benefit in periodic re-tenderingprocedures.

31. Deciding upon the extent of the maintenancecontract is a fairly complicated process. Historically,intruder alarm companies were content to set aprice for a year's routine maintenance, but levyadditional charges for ad hoc replacements and call-outs. Often the customer has been tied to theinstalling company's maintenance contract andsuffered the expense of the business that unreliablealarm systems have generated for the companiesengaged in maintenance activities.

32. In recent years the intruder alarm industry hasbeen under increased pressure to improve standardsof reliability. Combined with technological advancesthis has produced a new generation of componentswith enhanced immunity to false alarms.Accordingly reliable intruder alarm systems can nowbe installed. In respect of a newly completedinstallation employing modern technology, theindustry is now more likely to direct the customertowards a fully comprehensive maintenancecontract, in preference to the historic 'maintenancewith repairs at additional cost' type. Trends willcontinue to evolve and the customer's maintenancepolicy needs to be flexible to readily adjust to themost advantageous method prevailing at anyparticular time. Depending upon the characteristicsof different installations, it may be most viable forthe customer to opt for both a fully comprehensivecontract and repairs at extra charge typeagreements, to suit any particular installation. Whenopting for a fully comprehensive arrangement it isessential that the customer's tender documents fullydefine the scope of the maintenance contract. Call-outs to a real intruder activation or user-inducedfalse alarms may reasonably be charged at additional

14

cost. However, the tender documents should invitetenderers to state their rates for the type of call-out,call-out time of day and day of week in order tofacilitate competitive comparison.

33. Where owners of multiple alarm installationshave established a large portfolio of highly reliablestandard alarm installations, it is probably mostcost effective to invite tenders for the basic routinemaintenance with call-out charges levied separately,in accordance with tendered schedule of rates.

34. The tender documents should include amaintenance specification, to meet as a minimumthe requirements of BS 4737 Section 4.2. Tofacilitate multiple installation tendering a scheduleshould describe the apparatus at each protectedpremises. It is not recommended that the premisesshould be identified at an early tender stage sincewidespread knowledge of the protected buildingsand hence the unprotected building stock creates asecurity exposure. The tender documents shouldinvite tenderers to submit a schedule of rates forevery conceivable repair or call-out function. Theprice for performing the basic routine maintenanceshould be separately detailed. It would bereasonable for quoted maintenance prices to holdfirm for a 12 month period agreement withsubsequently indexed linked fluctuations in theremaining years of the contract period.

Monitoring policy

35. Central station monitoring is not an absoluterequirement for every intruder alarm installation.Local audible alarms together with a 999 auto-tapedialler may adequately meet the required level ofsecurity and be more cost effective. LEAs with largenumbers of intruder alarm installations should havea clear policy for determining when central stationmonitoring is a justifiable requirement.Furthermore, the policy should define proceduresfor obtaining the required level of monitoring andalso retain contractual freedom for future changes toenhance monitoring facilities or move to morecompetitive terms. Where large numbers of intruderalarm installations are owned, the viability ofestablishing an around the clock in-house centralmonitoring station should be evaluated. Centralstation costs have been saved in one southern countywhere the local fire service has agreed to receive theintruder alarm calls and subsequently alert the localpolice.

36. In determining the break even point at whichan intruder alarm installation can be justifiablyconnected to a monitoring service, the servicecharges need to be evaluated against the level ofsecurity and usefulness of the monitoring facilities

15

provided. Appendix 6 of this publication "centralmonitoring stations" describes the stations'functions. Essentially, the required signallingbetween the premises and the central stationprovides a level of assurance that the alarm systemis in operating order and that integrity exists in thealarm system communication links. This achieves asuperior level of security to that attainable with the999 auto-dialler, and exclusive telephone linearrangement. Additional benefits may enable thekeyholder, in conjunction with the central stationoperator, to reset the system, following an alarmcondition, thereby eliminating the need for animmediate service engineer's visit to reset thesystem. Many fault conditions can be automaticallyreported to the control station thereby ensuringprompt remedial action. If an alarm signallingattempt fails, further digital dialling attempts aremade automatically and may include alternativetelephone line routes. Monitored, direct, privatewires increase levels of security further. Facilities fornon-alarm data monitoring can record opening andclosing events and the relevant user codeidentification. Fire alarms, lift alarms, heating, andother building services may be beneficiallymonitored. In particular, scope exists where thebuilding stock contains automated services that mayeasily lend themselves to remote conditionmonitoring. In preparing a policy for using centralmonitoring services it is therefore, necessary todetermine the usefulness of the facilities available.

37. Schools are of varying size and are located ingreatly differing areas of risk. Small and mediumsized schools in low risk areas may be most cost-effectively protected by an alarm system connectedto a conventional 999 auto-tape dialler. Where ahistory of break-ins exists, or if fairly valuableproperty is in situ, the ordering of an exclusiveex-directory telephone line, connected to the 999auto-tape dialler, should satisfactorily meet securityrequirements. Large schools and further educationestablishments increasingly contain computers andaudio visual equipment and are usually a high risk.Accordingly, central station monitoring cannormally be justified for this type of premises. Localeducation authorities need to assess the potentialloss and risk applicable to any particular building.Therefore, the policy on central monitoring shouldbe flexible to allow for the special needs ofindividual buildings.

38. To achieve future cost effectiveness, anycentral monitoring arrangement must contain thefreedom of choice for future monitoringcommitments. For the multiple user of centralstation facilities, benefit can be derived fromtendering on a block system for the connection of alarge number of intruder alarm systems to amonitoring service. Any contract or monitoring

7

agreement should respect this need to consider andrespond to future options.

39. It may be possible for LEAs with a largenumber of intruder alarm systems to beneficiallyestablish their own in-house central monitoringstation. The savins in the recurring charges leviedby monitoring contractors must be evaluated againstthe expenditure of establishing and maintaining anin-house monitoring station. The case forestablishing an in-house station will to a largeextent depend upon the geographical area of theLEA. Where the building stock is predominantly inareas that suffer from high crime rates and wherethe building stock has a history of theft and arsonattacks it is likely that central station monitoring isjustifiable. Accordingly, where monitoring isrequired for a significant number of premises, in-house monitoring should be considered. LEAs mustassess their own break-even point at which in-housefacilities become viable. The benefits of in-housemonitoring include the facility to economically addevery new alarm system to the monitoring station.Also, apparently low risk buildings can be cost-effectively monitored. Data storage methods providea history of events for every building, includingalarms, opening and closing times. In conjunctionwith appropriate software, alarm systemmaintenance and repair can be controlled andmonitored. Additionally intruder alarm systemadministration and financial control can beincorporated in the software package to include theraising of orders and invoice authorisation.

40. The viability of in-house monitoring alsodepends upon the requirement for additional in-house staff resources to operate the monitoringstation on a 24 hour rota. Some LEAs will alreadyhave a 24 hour security or emergency desk to whichthe monitoring terminal can be added. However,additional staff resources may still be needed toensure an adequate level of VDU terminalsupervision.

41. One LEA that operates its own central stationhas 250 intruder alarm systems monitored.Usefully, some other monitored items include liftalarms, sewage pump failure alarms, and buildingservices such as low temperature alerts to warn ofheating plant failure and thus prevent frost damage.In 1985 the monitoring equipment cost theauthority £12,000 and in 1987 the annualcomprehensive maintenance charge wasapproximately £1,200 which included regularsoftware updating. The full software packageprovides for the efficient administration of all theLEA's alarm systems. Placed with externalorganisations, the LEA estimates that their annualmonitoring charges would currently be in the orderof £20,000. It is imperative that any proposal to

8

establish an in-house monitoring station is fullyassessed on the facts applying to the individualowner of multiple intruder alarm installations. Inrespect of this, liaison should be carried out with allinterested parties, including the local police force.Fact-finding visits to existing users of in-housemonitoring systems can be highly beneficial. Theconsequences of a system failure are extremelyserious, therefore system reliability and goodmaintenance support are essential requirements.

16

4 Design d ztVlzdier z_anam syMeras

42. A well-designed intruder alarm system willsatisfy the following basic essentials:

Provide early detection of the presence of anintruder or an attempt to gain unauthorisedentry.

A tolerance of environmental backgrounddisturbance whilst providing high levels ofdetection sensitivity ensuring that false alarmfactors are beyond the range of detection.

Effectively communicate alarm signals.

43. Intruder alarm systems are a building servicescomponent. Other services, heating, lighting andventilation are designed to a combination ofstatutory standards and recognised guidancedocuments.

44. BS 4737 Intruder Alarm Systems in Buildingsdefines essential standards for the system itscomponents, and their installation, but is notintended to provide guidance on the extent of anyintruder alarm system. Parts of BS 4737 have beenin the course of revision during the preparation ofthis publication. Readers are advised to refer to thelatest available edition of BS 4737. Unlike otherbuilding services the designers of intruder alarmsystems must determine for themselves the level ofnecessary security and the appropriate extent ofindividual alarm systems. Consultation with thelocal crime prevention officer can help inrationalising these considerations.

45. The designer's prime function is to maximisethe amount of protection against intruders fromfinite financial resources. Often, the designerpossesses a list of non-alarmed buildings that arefrequently the targets of theft and arson attacks. Atthe same time, protection may require extending atother buildings where the level of potential loss hasincreased.

46. Increasingly, community use of schoolsimposes greater demands upon the flexibility ofintruder alarm systems. In many cases there will bea long-term advantage in selecting a system thatcan be readily zoned to suit changes of occupancypatterns. This will enable unoccupied areas to beprotected whilst other areas are in use.

47. The design process involves the assessment ofrisks and determination of the optimum level qfinvestment in security measures and then app4,ing

1 7

the technology in intruder alarm systems withexpert knowledge. DES Building Bulletin 67 CrimePrevention in Schools Practical Guidance offers adviceon reducing risks and also contains examples of riskanalysis. However, in many practical situations,historical data will influence the allocation offinancial resource expended in intruder alarminstallations. In respect of this a system of datacollection should identify the value of loss and thenumber of attacks upon the individual premiseswithin the building stock. Effectiveness of differentintruder alarm installations should be regularlyevaluated thereby providing a valuable feedback toimprove future design work.

Technical aspects

48. It is recommended that LEAs should try todevelop a common technical standard for all theirschools rather than adopt a particular proprietarysystem. This makes available to the customer thebenefits of competitive tendering. Detectors,controls and ancillary components should be definedby their performance specification or by an approvedlist of proprietary products. Almost certainly, analarm system will require numerous additions andadaptations throughout its operational life. It isadvantageous if the finished installation lends itselfto future revisions by competitive tenderingprocesses. In respect of this an intruder alarminstallation can be as flexible as an electric lightingor power installation. Contractors may submit theirown conditions stipulating that the alarm controlpanel and other essential parts of the installationwill not constitute an outright sale, but will besupplied only on a rental agreement. Acceptance ofthese terms may prohibit competitive tendering forfuture alteration work.

49. Components must be selected for theircompatibility with their working environment.Temperature, humidity, radio signals, vibration,sunlight, air motion and passing vehicles are just asmall number of the random factors that maystimulate a false alarm, or reduce the sensitivity ofdetection. Component selection may be aided byreferring to the technical appendices containedherein describing each common form of detectionagainst which manufacturers' specifications may becompared. It should therefore be possible for thedesigner to specify the type of detection technologyand its required performance in terms of range,

9

sensitivity, and level of false alarm immunity.Alarm control panels and communicationequipment are similarly described enabling thedesigner to consider the broad options.

50. The quality of installation workmanship mustbe fully defined. Where the designer is responsiblefor a large building stock there is considerableadvantage in producing a standard specification. BS4737: Section 4.1 includes subsections specificallyreferring to the planning and installation of intruderalarm systems. However, it is still incumbent uponthe designer to specify particular requirements. Inthe absence of a detailed technical specification andlayout drawings, installers will use their owncommercial judgement to determine installationstandards. Typically, interconnecting cables may besimply clipped to the surface, enclosed in alightweight conduit, trunking or laid in floors andceilings. The cable routes chosen may be the mosteconomic to the installer and not be fullysympathetic to the aesthetics of the building. Thefollowing list schedules appropriate items forconsideration for inclusion in a standardspecification:

General conditions of contract and preliminaries

Requirements for all materials to be used,including control panels, communicators,detectors, zone omit units, shunt locks, wiring,conduits, trunking and fixings

Requirements for ordering telephone lineconnection and central monitoring stationservices

Agreed procedures for informing the localpolice that the new alarm system is in operation

Liaison with building user to determineappropriate first and final entry route

m Design considerations to comply with BS 4737and where appropriate, the latest edition of theIEE Regulations for Electrical Installations.

Define proposed cable routes and method ofcable fixing throughout entire length ofcable route. It is good design practice toensure that the maximum system voltagedrop does not exceed 1 volt between anytwo points, thereby ensuring detectors areworking within design parameters.Generally, cables below a height of 2metres require physical protection againstmechanical damage.

ii Ascertain user's need for shunt lock, zoneomit facilities and 24 hr protection whereproprietary zone omit units may benecessary.

iii Prescribe the use of catenary wire to carry

10

overhead alarm cables. Similarly, defineminimum cable depth for undergroundroutes and type of cable and protection tobe employed. Cable joints shall beterminated in tamper resistant terminationboxes.

iv Coordinate the provision and position of thenew power supply to serve the alarmsystem. Comply with requirements tophysically segregate alarm signal wires frommains voltage wiring.

Define proposed position of detectiondevices, with drawings as necessary. Includethe use of dummy bells, visible on allexternal elevations. For new works,coordinate a concealed conduit installationwhere feasible.

vi Make due allowance for the system topossess flexibility and be sympathetic tofuture changes, particularly in respect ofchanging patterns of occupancy.

Provision of user instructions that are easy forthe layman to understand. Also specify need forthe installing company to educate usersregarding the operation of the alarm system

Installation tenderers to competitively submitdetails of their maintenance, central monitoringand call-out charges in respect of the alarminstallation tendered for. Seek confirmation ofthe method for calculating future increases inthese recurring service charges. Where required.,state that it should be the customer'sprerogative to terminate any maintenance orrental agreement by giving reasonable notice

z Specify that the system must be supplied on anoutright ownership basis, unless the customer isfully prepared to accept the installingcompany's rental conditions

Refer to the need for the compliance with theHealth and Safety at Work Act and the statutoryrequirements applicable where asbestos is foundto be present

51. The above list is intended as a general guidefrom which the designer may tailor a particularspecification.

linst ation

52. The designer's documents should not onlydetail technical component requirements but mustalso stipulate the standards of workmanship andmethod of installation. Basic standards vary betweeninstalling organisation and the individuals employedupon any particular project. It is therefore

18

incumbent upon the customer to clearly definerequirements, within the tender documents andsubsequently diligently supervise all stages of theinstallation work. Similarly, the personnel assignedto the installation should be of "good character"and respect the confidential nature of theiractivities.

53. The majority of intruder alarm installationsare carried out by private contracting companiesmany of whom are on the National SupervisoryCouncil for Intruder Alarms, (NSCIA), roll ofapproved installers. The NSCIA was established in1971 with support from insurers and some of thelarger companies involved in the installation ofsecurity alarm systems. As a non-profit makingbody, it has produced a code of practice for thedesign, installation, operation, maintenance andservicing of intruder alarms. The NSCIA operatesan inspection board to implement itsrecommendations and maintain standards ofworkmanship. For installers to gain entry on theroll of approved installers they have to demonstrateconformity to a required standard of businessmanagement. Their completed installations and 365days per year call-out service must comply with therequirements of BS 4737. The ElectricalContractors' Association (ECA) and the ElectricalContractors' Association of Scotland has formed asecurity group. A function of the group is to form aregister of electrical contractors and securityinstallers capable of installing, maintaining andsupporting security systems to the requirements ofBritish Standards(BS 4737 for intruder alarms). Inconjunction with this a code of practice has beenproduced by the ECAs and a procedure forinspection has been established.

54. The British Security Industry Association(BSIA) comprises some of the largest manufacturersand installers of security systems. Its board basedmembership includes the fields of CCTV, guard andpatrol services. It is a self-regulatory tradeassociation that aims to advance standards inintruder alarm systems as well as the other securityfields. All BSIA security system manufacturers andinstallers are required to comply with BS 4737 andBS 5750. A customer complaints procedure operatesunder which inspections are carried out.

55. Factors relating to the size of a company or itslength of time in business may render many localcompanies and new enterprises unacceptable forinclusion upon a roll of approved installers.However, many of these developing companies canbe competitive in producing work to a satisfactorystandard in their effort to gain a share of themarket. The Inspectors Approved Alarm Installers,(IAAI), has various membership categories, tocomplement companies of different size andcapability. Guidance is offered to new or developing

companies, in meeting the requirements of theIAAI inspection process. Whichever course thecustomer follows it is wise to seek references andotherwise ascertain the standards of workmanshipand service support relative to any individualcompany that is intended for inclusion on a tenderlist. In respect of this the local police force orrelevent insurance company may advocate the use ofalarm companies with membership of a trade body.However, for LEAs, statutory regulations mayprevent the use of member only clauses in contracts.Before an installation is commenced the customer'ssupervisor, together with the installer's supervisor,should agree the extent and details of the work inprinciple. Accordingly, the installation processshould be arranged to create the minimum ofdisruption to the normal business of the schoolpremises.

56. Generally the designer's documents can onlyindicate the approximate location for detectors andexact positions may be mutually agreed on site toproduce the most effective, false alarm resistantform of intruder protection. Intermediateinspections help to ensure compliance with thedesigner's requirements and also minimise theamount of any corrective work.

57. The installer should programme the workensuring that any requirement to order a telephoneline or liaise with the local police is arranged to suitthe proposed commissioning date on the alarminstallation. Similarly arrangements must be made

to coordinate the provision of the mains powersupplies and obtain user instructions and operatingmanuals, and where required, type-written "zone"location charts.

58. All components should be installed in a goodworkmanlike manner both in accordance with therelated manufacturer's instructions and therequirements of BS 4737. Typical applicationrequirements are detailed in the appendices for thedifferent technologies of intruder detection. Theprocess of site supervision should ensure thatcomponents are adequately fixed and that time-saving reliance placed upon adhesive fixings andmasonry nails is not permitted where there is anadvantage in providing a more permanent form offixing. When mortice shunt switch locks arespecified, the fitting should, preferably, beentrusted to a skilled locksmith or joiner.

59. Once the installer is satisfied the completedinstallation meets all requirements, the customer'ssupervisor should be invited to make a finalinspection and if necessary produce a snagging listof defects and outstanding work. When theinstallation is fully to requirements commissioningshould be carried out.

111

Comnissoming

60. Commissioning must ensure that all theinterconnected components of an intruder alarmsystem operate within the parameters defined by thecomponent manufacturers. To verify thisrequirement the appropriate form of test instrumentshould be used to quantify the electricalcharacteristics of the system and aid settingadjustments. Typically, breaking glass detectors andsome forms of volumetric detection may becommissioned with the aid of proprietarycommissioning equipment. More practicalcommissioning includes "walk testing" and otherintruder simulation to aid detector sensitivityadjustments and confirm the effectiveness of thesystem to detect the presence of an intruder. Inconjunction with this theoretical, out of range,walk testing and the deliberate operation ofbuilding services systems such as lighting, heatingand ventilation should prove that the systempossesses adequate immunity to environmentallyinduced false alarms. Where possible thecommissioning environment should be similar tothat prevailing during all periods when the alarm isarmed. Unfortunately, not all environmentalfactors can be simulated, particularly weathervariables. An experienced commissioning engineerwill possess an ability to broadly assess the effects ofsuch variables and compensate detection sensitivitysettings accordingly. For example, some forms ofvolumetric detection are most sensitive when the airis still and the environment is cool.

61. The various technologies of detectioninherently have their own sensitivity or immunityto the whole range of environmental factors.Environmental factors can very often have asignificant effect upon the sensitivity of the form ofdetection to real alarm conditions. This should beconsidered in conjunction with all of the prevailingenvironmental conditions at the time ofcommissioning.

62. Digital communicators, 999 auto tape diallersor direct telephone lines should be tested under asimulated alarm condition. Where communication isextended to police it is imperative that testingmethods fully comply with the requirements of thelocal police force. Digital communicators and directlines are tested through to the central station. Only999 Auto Diallers are tested through to the police.

63. In some instances a local police force mayrequest a time delay to precede the activation of theexternal audible alarm. The commissioning engineershould seek the customer's agreement of thisproposal before implementation. Time delay maygive vandals and arsonists opportunity to doextensive damage.

12

64. Where local audible alarms create a nuisancelegal action may be taken under the Control ofPollution Act 1974. As a precaution against suchaction and to reduce the likelihood of unnecessarynoise it is desirable to automatically limit thesounding duration of an external audible alarm to amaximum period of 20 minutes. The local audiblealarm should be auto-resetting, when the controlpanel is manually reset such that the alarm is readyto sound upon a subsequent activation. However, inremote locations or where there is a request for alonger duration of audible alarm an extension of the20 minute period may not be contested by the localenvironmental health officer provided false alarmactivations do not create a nuisance.

a Meirdsmanze rnrudez. ca_ET_CM sys2a s

65. Increased levels of false alarms and failures torespond to the presence of intruders are typicalsymptoms of inadequately maintained intruderalarm systems. As with any other passive safety orsecurity system there is a dependency upon a properlevel of maintenance to ensure that the alarmsystem responds to a future emergency. BS 4737:

Section 4.2. Code of Practice for Maintenance andRecords, details requirements applicable to intruderalarm systems in buildings.

66. There are two modes of maintenance, pro-active and reactive. In terms of value for money andoptimum levels of security, planned, preventativemaintenance increases system reliability, lowers falsealarm rates, and minimises the waste of resourcesdevoted to reactive maintenance in response to call-outs to attend to system faults and false alarms.Preventative maintenance visits can usefully becoordinated with a short period of user educationthereby updating the keyholder's knowledge andeducating new keyholders, with the consequentialbenefit of reduced levels of user-activated falsealarms.

67. Preventative maintenance works should becarried out to a written schedule at regularminimum intervals of six months for systems withremote signalling and annually for systems withlocal audible alarms only.

68. The integrity of the customer's security mustbe respected at all times. Maintenance visits shouldbe by prior appointment. The customer's on siterepresentative is advised to check the identitycredentials of all service personnel who in the courseof their duty should be in possession of a currentidentity card, as issued by their employingorganisation. Where it is proposed to test localaudible alarms or remote signalling extended to thepolice, it is essential to adhere to procedures thathave been previously agreed with the local policeforce. Similarly, the police should be advised of theoperational status of any alarm installation andchanges such as premises ownership, new keyholdersand abandoned or removed installations. Thequality of servicing personnel training andcontinued education is of prime importance. Inrespect of this, the customer should seek assurancesfrom any prospective maintenance organisation.This education and training criterion equally appliesto organisations who perform their own in-houseinstallation and servicing functions.

0

69. Security is an all-embracing concept and anysingle weakness can create a breach of total security.The building owner's maintenance regime shouldinclude non-alarm items such as doors, windows,fences and external security lighting

70. The extent of the work required under themaintenance schedule is proportional to the size andtechnical complexity of the alarm system.Computerised and condition monitoring"intelligent" systems extend the basic maintenanceschedule. Essentially, a visiting engineer willpossess a computer-issued condition report directingthe engineer to investigate and resolve reportedconditions of near false alarm and possible deviationfrom the system's electronic parameters.

71. A basic routine maintenance schdule includesthe following items.

Instrumentation testing of detectors to verifyconformity to technical parameters andconsistency with previously recordedmeasurements.

LI Power supplies and voltage measurement atvarious system locations for conformity todetector operational parameters.

LI The satisfactory operation of detection devicesand any necessary.fine tuning of sensitivityadjustments.

LI Full visual inspection for physical damage, loosefixings, tampering evidence, or deterioration offlexible connections.

LI Condition testing of secondary batteries andreplacement as necessary together with theroutine replacement of systems employing drycell batteries. Batteries utilised in wire-freealarm systems should be replaced in accordancewith the equipment suppliers' recommendationsand within the requirements of BS 6799.

LI Verification of the satisfactory operation of localaudible alarms and the replacement of theirintegral, sealed, secondary batteries before theexpiry of their rated service life expectancy.

LI The correct operation of auto-tape diallers,digital communicators and the communicationmedium.

LI The functioning of the entire combined alarmsystem throughout all its stages ofinterconnection.

13

In addition to the basic scheduled items detailedabove, further tests should be carried out inaccordance with the recommendations of equipmentmanufacturers, BS 4737, or any other appropriatecodes of practice, as produced by individualmaintenance companies or relevant tradeassociations.

72. At any moment an alarm condition may beinstigated by an intruder, environmental factor or asystem fault. Also an anomaly in the system'scondition may become apparent whilst the system isin the occupied, disarmed status, or when thesetting procedure fails. In respect of theseconsiderations it may be required at any time toreset automatic communication equipment andrepair or isolate a faulty section of the alarminstallation, thereby restoring the maximumamount of the intruder alarm system back into use.In the event of a false alarm activation every effortshould be made to determine and hence eradicatethe cause of the false alarm before re-arming theintruder alarm system and resetting any associatedremote signalling apparatus. Where remote alarmsignalling is extended to the police, resettingprocedures should fully comply with local policeforce policy. BS 4737: Section 4.2 Code of Practicefor Maintenance and Records, requires that remotesignalling equipment should be reset by a memberof the maintenance organisation's staff or by thecoordinated efforts of the subscriber and centralcontrol.station where this alternative method isappropriate. For schools it is usually the schoolkeeper that fulfills the subscriber's role. BritishStandards require that the maintenance organisationshould, under normal circumstances, reach theprotected premises within 4 hours from the time ofthe request to attend. The maintenance organisationshould establish and maintain a record log ofmaintenance and alarm events for each alarmsystem. Any written or computer records should beprotected from unauthorised access.

73. 'Engineer reset' is an expression used withinthe alarm industry to imply that an activated alarmsystem is subsequently reset by an 'engineer'employee of an alarm maintenance company. Often,this task involves little more than pushing a buttonand confirming the reason for the alarm activation.Where a fault exists it is usually possible to operatethe alarm control panel to restore most of thesystem and temporarily isolate only the failedsection of the system. A full repair is then carriedout during normal working hours. Some LEAs havefound economic benefit in fulfilling this resettingrole for themselves, since as owners of multiplealarm systems considerable costs can be incurredfrom contractors call-out charges. However, in mostareas the agreement of the local police is necessaryand is more likely to be forthcoming where the

14

LEA can demonstrate competence in managing itsalarm systems coupled with a low rate of falsealarms.

74. Owners of multiple intruder alarminstallations are advised to retain their own recordsof maintenance and alarm activation for eachindividual system. Auditing methods maysubsequently be used to identify troublesome alarminstallations and effect remedial action. Suchinformation may collectively reflect upon futuredesign considerations and lists of approvedinstallers. Furthermore when historical records arein the sole possession of an outside organisation,valuable data may be lost subsequent to changesfollowing the future competitive tendering ofmaintenance contracts.

75. Schools should keep a standard log book forrecording events. Retained in a secure place, onsite, available to the keyholder, it can containuseful information that will greatly assist bothexperienced and new keyholders. Typically,premises address, emergency telephone numbers andinstallation equipment details are included as apreface to the log book. Maintenance activity andalarm events are logged against the relevant circuit,area of protection, and specific detector details.Recording methods may be easily tailored to suitthe requirements of the particular LEA.

"2

6 Operation of intruder alarm systems

76. Human factors have a great impact upon thesatisfactory operation of intruder alarms. Lack ofdiscipline will cause security exposures resultingfrom alarm systems not being properly armed andthe occurrences of excessive false alarms leading tothe withdrawal of police response. Approximately95% of intruder alarm activations are attributed tofalse alarms. Technical advances in hand with gooddesign and installation practice will drasticallyreduce the occurrence of equipment induced falsealarms. However it is up to the user to employoperating methods that complement the high levelsof technical standard that can now be achieved.

Setting of alarm system controls

77. Users of intruder alarm systems are generallynon-technical people. To carry out the control panelsetting procedure and subsequently reach and securethe final exit door, within a defined time, can be adaunting task for many people. The temptationmay be to take a chance and not activate the alarmsystem, particularly where during previous settingprocedures, accidental false alarms have alreadyoccurred. Inevitably, this lax situation continuesuntil a loss investigation reveals that the alarmsystem has not been properly used.

78. User education is vital. LEAs should ensurethat their tenders for alarm installations include aprovision for adequate user training. Only byfulfilling this criterion will the user have theconfidence to master the operational procedures.Frequently there will be a group of people withresponsibility for operating the alarm system atdifferent scheduled times. A formal managementprocess should ensure that knowledge is sharedwithin the operating group guaranteeing that new orrelief staff are fully familiar with the alarm systemcontrols.

79. LEAs can benefit by standardising upon ashort list of suitable proprietary control panels. Thisensures that relief and other staff transferred tounfamiliar premises are already familiar with thestandards of controls. Further to this the LEAsin-house engineer or security specialist maybeneficially be charged with the responsibility tosupport the user educational needs. This hasparticular bearing where an intruder alarminstallation is either new or has undergonesignificant modifications.

r

User induced false alarms

80. False alarms induced by the user are avoidableand should therefore be eliminated by the adoptionof good management procedures. The operator of anintruder alarm system should follow a definedroutine prior to activating or de-activating thealarm system. Before attempting to set the systemall protected doors and windows should bephysically secured. A visual inspection of protectedareas should confirm that heaters and fans areswitched off together with other false alarm-inducing environmental factors. Similarly theinspection should check that boxes and othermaterials are not stored in an insecure mannerwhereby they may be liable to move under theinfluences of a draught or vibration. The final exitroute should be clear and free of stored materials,wedged doors or other factors that may impedemovement through the exit route. The operator ofthe alarm system should be fully prepared beforeattempting the entry procedure. Prior to openingthe first entry door the operator should ensure thatall other relevant keys are readily available to gainaccess to the controls and disarm the control panel.In respect of this the operator will need to haveavailable keys to any intermediate doors togetherwith the operating key for the control panel or beprepared to enter the appropriate code upon acontrol panel digital keypad.

81. Sensible methods of key management greatlyreduce the level of user induced false alarms. Often,a legitimate member of staff may possess a side dooror other secondary key and use it to make entry tothe school during unoccupied periods. Teachers areknown to visit schools during holiday periods,perhaps to tend animals and plants, or to monitorlong-term laboratory experiments. LEAs shouldensure that out of business hours access is by priorarrangement with the building keeper or otherperson responsible for operating the alarm system.As a basic matter of security, keys should only beavailable to those members of staff with an essentialneed. In respect of this authorised keyholdersshould not casually delegate responsibility foropening or securing the premises.

82. For many premises zero false alarms can be areality. Essentially intruder alarm installationsshould be of high standard and school staff must bemade aware of the importance of enforcing theeffective management of intruder alarm systemstogether with the whole concept of building security.

15

me studios

The four studies represent typicalexamples of good practice that can befound in different types of schools.Taken from various parts of Englandthey demonstrate cost effective intruderalarm installations that have beendesigned to balance the amount ofprotection provided to suit the amountof risk involved. This method achievesthe optimum amount of protectionwhere only limited finance is available toprovide protection in a number of highrisk schools.

ekl;

<CD

16

SCHEDULE OF SYMBOLS

Passive infrared wall mounted detector.

3600 ceiling mounted PIR detector.

Curtain or narrow angleceiling mounted PIR detector.

Ultrasonic movement detector.

0

1111

Magnetic contact.

Continuous wiring in tubes.

Breaking glass (vibration type) detector.

Intruder alarm control panel.

Local audible alarm.

Dummy local audible alarm (box only).

Symbols have been devised for the purpose of this publication.BS 4737 is currently being revised to include a section on symbols.

, L

ASE UD

A large middle school in the Midlands

83. The school was constructed during the 1980sand derives most of its intake from a nearby largecouncil estate. The site is also occupied by a sportscentre and two other schools, all of which hadpreviously been provided with alarm systems.

84. The rear elevations of this school face anexpanse of open fields at the boundary of which is achoice of getaway routes for the intruder. Histori-cally the school has suffered from a very high rate ofbreak-ins resulting in theft and vandalism. This wasconsidered to be partly due to the geographicalvulnerability of the school and the fact that the olderbuildings on the same site were already protectedwith intruder alarm systems.

85. In the 12 months since the installation of theintruder alarm system there has been a drasticdecrease in the number of break-ins. When break-ins do occur the alarm system has always activatedand caused the intruders to make an empty-handedretreat. Unfortunately, the elevated position of the

Curtain PIR detector positioned toCurtain PIR detector positioned to avoid kilns, but detect transverseavoid heater, mobiles and car movement between points of entry.headlights.

school offers the intruder a vantage point fromwhich the intruder may observe the police approach-ing at considerable distance and therefore haveample time to effect their escape. However thesounding of the local audible alarm and theapproaching police car means that the attemptedtheft is abandoned.

86. Protection has been provided to circulationand target areas at ground floor level with a smallnumber of detectors situated on the first floor whereadjacent flat roofs enable easy access to break in atfirst floor level. The illustrated plan has beenmarked up to indicate the location of particularintruder alarm components including the use of therecently-introduced ceiling-mounted type ofdetector where there is often an advantage inreduced levels of physical damage. In general, thephilosophy of this particular example has also beenapplied in the other examples of good practicedetailed herein. In 1986 the alarm system costapproximately £1,900 to install.

Long range PIR detector foreconomical trap protection located forminimum cable length

PIR/microwave dualtechnology detectorused in long draughtycorridor.

Wide angle PIRdetector positioned Local Audibleto sense transverse alarm locatedmovement. in prominent

Magnetic contact position

fitted to finalexit door

Ultrasonic detectors usedin rooms with highSummer time temperaturepositioned to senseradial movement

Wide angle PIR'detectorpositioned toavoid carheadlights butsense transversemovements.

HALL

Control panel locatedbehind lockable door withinthe protected space

Economical protectionin hall with 360* ceilingdetector

Vulnerable Midden doors fitted'th a magnetic contact.

PIR detector used to providetrap protection in circulationareas. Positioned to sensetransverse movements.

Dummy Audiblealarm box. _ ---

KITCHEN

Food store roof light PIR ceiling mounted curtainprotected with detector located away from steamcontinuous and heat.wiring in tubes

17

cimr, 67-arr

A small Victorian first and middle school in London

87. The school fronts onto a well-lit residentialroad but its side and rear elevations face an openindustrial site, a secluded public footpath and anaccess route to the rear of commercial premises andare therefore generally hidden from public view.This school was persistently troubled by break-inswhere the intruders were intent upon theft, vanda-lism or arson. The alarm system was installed in1985 and in the following two years there was onlyone incident of a break-in which resulted in damageto windows and the school piano which was locatedin the hall. Subsequently, this particular intruder

Alarm control panellocated behind lockabledoor within the protectedspace

Cost effective use of long rangePIR detector provides trapprotection to ground floorcirculation area and also guardsboth access routes to first flooroffices.

was later arrested during a break-in at anotherschool when the intruder alarm system alertedpolice. This basic alarm system, with scope forfuture extension, was installed for less than £500.Illustrated is the very effective use of just threedetectors where one corridor detector at groundfloor level not only provides trap protection to theground floor but serves to detect intruders attempt-ing to gain access to the first floor offices. Financehas recently become available to economicallyextend the system to protect the side and rearelevations.

117

Both Head Teacher officesprotected with wide angle PIRdetectors, located to sensetransverse movement. Magneticcontact fitted to final exit door.

18'ILL 2 G

j-Ac@,R1L

)

A large comprehensive school incorporating a continuing education centrein Southern England

88. The ground floor plan only of this three-storey1950s building is illustrated. In more recent years,additional buildings have been added to cater for thelocal rise in pupil numbers. The school contains agreat deal of valuable items and is particularlyvulnerable to intruders since three of its elevationsare hidden from public view and back on to fieldsthrough which there is a network of public foot-paths. Within the constraints of limited finance,the school was considered too large to providecomprehensive protection. With this in mind it wasdecided to install trap protection in circulation areaswith point protection in high risk target areas.Historically, there had been a number of break-insat first floor level where adjacent single-storey

Long rangePIR detectorsin corridors

Control panelinside lockableroom within theprotected space.

Final exit door fittedwith magnetic contact.Conveniently, thisdoor is near tocaretaker's house

(f)

LAB

1

4

flat roof buildings had been used to gain access. Asmall number of detectors have therefore beeninstalled to provide trap protection at first floor levelwhere it meets adjacent flat roofed areas. The schoolsuffers from noise and vibrations caused by low-flying aircraft and for this reason the use ofmicrowave or ultrasonic detection devices was notconsidered. The system has been highly effective as adeterrent having significantly reduced the level ofbreak-ins. Arrests have resulted from the policeresponding to the alarm system's signal. In 1985 thesystem cost less than £1,600 and has proved itselfeffective and reliable. However the low cost controlpanel is not convenient to flexible zoning or changesin patterns of occupancy.

Mr"

Wide angletrap protectionin circulationspaces

WI1111113

!la

Vulnerable doors fittedwith magnetic contacts

27

,Aircraff noise and induced vibrationprohibits ultrasonic detection.Temperature compensated PIR detectorused in rooms with high levels of solarheat gain.

MPUTERS

I COMPUTER

Wide angle PIR detector, positionedto sense transverse movement andavoid car headlights.

19

TILtrr%

CDT Centre at a North of England school

89. It was decided to dedicate one of the two1930s built school buildings to form a CDT centre.Due to the very high risks associated with valuableequipment it was considered worthwhile to install ahigh degree of protection against intruders. Occu-pancy periods are considerably extended due tocommunity participation in CDT subjects. Aseparate intruder alarm system has been installed ineach school building in order to ease the problemsassociated with managing the security of twobuildings with greatly differing occupancy pat-terns. The schools are provided with multiplexcontrol panels which have been found useful incatering for the flexible zoning requirements to suit

Ultrasonic detector used in smallroom subjected to high levels ofsolar gain during the summerholiday period. Positioned to senseradial movement.

Ceiling mounteddetector in hall isless likely to sufferphysical damagethan wall mountedtype.

the changing patterns of use. During the two yearsthat the system has been in use there have been no falsealarms either induced by the users or technical failure.

90. Good forward planning ensured that the alarmsystem was installed at the same time that expensiveCDT equipment was installed. Recognising theextent of the risk it was decided to provide intruderalarm protection from the onset. There have been asmall number of break-ins but they have alwaysbeen abandoned upon the activation of the alarmsystem with the losses being restricted to minordamage only. In 1986 the system cost approxi-mately £1,400.

Control panel located within Dummy localthe protected space of the ry 41( audible alarm.audio visual aids store. Alsoconveniently close to final exitdoor.

r1-1EA-D

HALL

101=sli agin=m0

Local audible alarm with strobeElight. Placed in prominent position.

20

OFFICE

Typical wide angle PIRdetector used in small/mediumsized teaching areas.

-7SCIENCE COMPUTE S COMPUTER

a aFinal exit 7)

COURTYARD

MUSIC

ART CRAFT

Typical cost effective perimeterprotection by narrow angle longrange PIR detector.

Q.)

PIR detectors positioned tosense transversemovement and avoid carheadlights.

APPENDICES

2 92 1

APPENDIX 1 Intruder detection devices

91. The devices used to detect the presence of anintruder are usually either electronic sensors ofmovement or electrical components that arepositioned to detect physical actions such as footpressure, doors opening, or glass breaking. Sincethe introduction of the microprocessor to securityapplications, movement detectors have become themost common forms of intruder detection. Table 2indicates the main factors that influence the rangeof detection and the false alarm risk.

92. This appendix describes many of the forms ofdetection starting with the three main types ofelectronic movement detectors.

ULTRASONIC 'VOLUMETRIC'DETECTORS

Theory of operation

93. Ultrasonic detectors use high frequency soundwaves to sense the presence of an intruder in aprotected space.

94. Early generations of ultrasonic detectors wereinherently unstable because they were adverselyaffected by ambient environmental factors.However, present day ultrasonic devices,incorporating microprocessors, are much morereliable and should be evaluated according to theirspecification and be objectively compared with otherdevices in terms of levels of security and theenvironmental conditions that relate to anyparticular situation. Correctly used, reliable, higherlevels of security can be achieved with the ultrasonicdetector.

95. Ultrasonic 'volumetric' movement detectorsperform three main functions:

Transmission of ultrasonic sound waves into theprotected space.

Reception of ultrasonic sound waves reflectedback from "mass" within the protected space.

Electronic processing of the received ultrasonicsound waves, using the transmitted signal as areference of comparison. The various stages ofprocessing analyse changes imposed upon thereceived signal. Changes have different

3 0

characteristics depending upon the factor whichacted upon the reflected wave. Withinlimitations, a human body can be electronicallydifferentiated from an enviromental disturbancesuch as air turbulence above a room heater. Thequality of this electronic filtering is the primefactor in establishing immunity to false alarmsand may eliminate the problem associated withearlier ultrasonic detectors.

96. Present day ultrasonic detectors are availablewith two separate alarm outputs: No. 1 to signal afull alarm condition; No. 2 is normally an"electronic switch" which enables a small current topass through a transistor within the detector tosignify an alert (near alarm) condition. When usedin conjunction with an "intelligent" or similarlycompatible control panel this electronic output canbe used to give advanced warning of environmentalfactors that "almost" activated an alarm condition.Additionally some detectors incorporate furthercircuitry that monitors the functioning of thedetector's components and creates an alert via theelectronic output when a detector's performancedeviates beyond a pre-set tolerance. This alsoprotects against accidental or deliberate masking(see glossary) of the detector. In high security areas,with a stable environment the electronic output No.2 may be used together with output No. 1 toprovide a very sensitive detector that will activatean alarm under either output mode. For highsecurity application, detectors are available that canbe tested remotely, whilst they remain actively inuse. However it is essential to ensure that detectorsand control panels are compatible for the optionsrequired.

97. Since the sensitivity (range) of an ultrasonicdetector varies with ambient temperature, somedetectors incorporate auto-compensators thatautomatically compensate for temperaturevariations.

98. Generally ultrasonic detectors are noteffective in rooms laiger than 10m2 or smaller thanabout 3m2. Where multiple detectors are used in asingle area, directions of coverage should beparallel.

Requirements for ultrasonic detectors

99. Ultrasonic detectors should generally meetthe following requirements:

23

TABLE 2

EFFECTS OF ENVIRONMENTAL FACTORS ON RANGE OFDETECTION AND FALSE ALARM RISK

FACTOR PIR U/S M/W

Level of ambient temperaturenears body temperature.

Rapid temperature change. 0 0

Level of humidity. 0 0

Air movement. 0 0

Weather conditions:thunder, lightning, hail.

0 0 0

Sunlight cast into detector. 0

Vibration. 0 0 0

Loud noise. 0 0

Heaters within field of coverage. 0 0

Soft furnishings and curtains. 0 0

Vehicle lights or other movinglights cast into detector.

0

Moving/falling objects: mobiles,Christmas decorations, curtains,posters, signs etc.

0 \.._.,(---, 0

Detection of movement behindglass and lightweight structures.

0

Movement of small animals andclose range insects.

Fluid flowing in non metallicpipes.

0

Stray detection of movement dueto reflections off metal surfaces.

0

Use of air lines or otherrelease of pressurised gases.

0

24

FALSE ALARM RISK

Slight 0Moderate

Severe

PIR = Passive infrared.U/S = Ultrasonic.M/W = Microwave.

EFFECT ON RANGE

Slight 0Moderate 0Severe

O Operate at a frequency above 22 kHz, typically25-35 kHz. Crystal controlled, piezo ceramic-transducers enable detectors to operate in thesame area without suffering from crossinterference.

Operate on the Doppler Effect (see glossary)employing processing circuitry to detectfrequency shift between transmitted signal andreceived signal, as may be caused by a movinghuman target.

Employ high quality active filtering to fullyand effectively discriminate between DopplerEffects due to "human intruder" andbackground environmental disturbance. Theamplitude time basis principle is inadequate forhigh levels of discrimination and accordingly itshould not be used.

EJ Be fitted with a range adjuster.

Provide temperature compensation forapplications below 12°C and above 30°C.

O Be capable of satisfactory operation under thefollowing environmental conditions:

Temperature: 10°C to + 50°CRelative humidity: 0% 90%N.B. Very low and very high levels ofhumidity extend the range of detection andmay expose a false alarm risk

fl Suitability for their application, either wall, orcorner mounted. Some detectors are universal.Special detectors with a splayed transmitterreceiver arrangements are necessary for ceilingmounted applications, in order to sensepredominantly transverse movement.

Incorporate a tamper circuit to activate an alarmcondition when the cover has been removedor the unit has been physically damaged.

Provide light emitting diodes (LEDs) for walktesting and optionally latch-on after an alarmcondition (but not prior to initiation of theentry procedure) until reset, thus indicating thepoint of intrusion or faulty detectoridentification. It is desirable that detectorsenable the walk test mode to be remotelyextinguished during normal occupancy, andonly respond when the control panel is set inthe test mode. Detectors and control panelsmust be chosen for their compatibility to matchthe options required.

Self monitoring circuitry with reporting ofdetector or environmental abnormalities may beused to advantage in conjunction with"intelligent" or other compatible controlpanels. Remote testing compatibility is useful.

To be secured to the base with a screw, and notrely solely on plastic lug retainers.

Environmental factors

100. Detector and environmental compatibility isessential to achieve high levels of security with zerofalse alarms. Although good quality detectors withcircuit processing incorporating active filtersinherently have some immunity to environmentalfactors, this must not be taken as a reason to permitultrasonic detectors to be misused and placed inunsuitable environments. This approach would leadto generally reduced levels of security and certainlyincrease the incidence of false alarms. The followinglist itemises environmental factors that couldadversely affect the operation of an ultrasonicdetector:

fl Minimum sensitivity (range) for a detector inits basic form would occur at about 30°C.Either side of this temperature the rangeincreases. At 5°C the range might be 30%greater and similarly at 50°C the range may beincreased by 10%, therefore some ultrasonicdetectors' range and performance can changewith environmental variations. BS 4737: part 3requires detectors to operate satisfactorily in0°C to 40°C bands. Detectors with temperaturecompensation reduce the amount of rangevariance with temperature.

The amounts of moisture in the air in the spaceprotected has a direct bearing upon the range ofdetection. At exceptionally high or low levels ofrelative humidity the ultrasonic detector's rangebecomes most extended. Minimum sensitivityoccurs at about 30% relative humidity.

Turbulence and draughts can induce a DopplerEffect upon the transmitted ultrasonic waveform causing false alarms. Modern detectorshave a reasonable degree of immunity to suchturbulence but this is unlikely to dealeffectively with air movement produced bymechanical ventilation, or fan assisted heaters.

E The surface to which the detector is fixed mustbe free from vibration. Do not mount detectorsto a surface that may have vibrations imposedupon it, whilst the alarm is active. In light-weight buildings partition walls may vibrateduring storm conditions. It is essential thatobjects within the range of detection do notproduce vibrations within the periods when thealarm is active.

Many mechanical and electrical pieces ofapparatus produce ultrasonic sound and thesemay result in false alarms. The designer shouldbe aware of the possibility of ultrasonic soundinfiltration from external sources. Even airblowing through a keyhole may produce awhistle with a harmonic ultrasonic wave form.Recently introduced electronic ballasts for

25

. oVip 2;110 1%.1.70.7.; re- ID .., 'it, ' fro, ;3 =Av.%to. gaf., -1:0.1An

I

I

ImEN

Plan views of typical coverage patterns.

27

3 4

(Figure 2 continued)

Front view of corner mounted coverage pattern.

Plan view of coverage pattern for ceiling mounteddetector. Ceiling must not be subjected to vibration.

28 4.0

fluorescent lighting operate at about 28 kHzand may produce ultrasonic sound wavescausing a false alarm.

The material composition and location of solidobjects within the protected space will affectthe performance of ultrasonic detectors. Softfurnishings absorb ultrasonic waves whilst hardsurfaces act as reflectors. Followingrearrangements it is essential that a "walk test"is carried out to ensure adequate sensitivity andthe absence of masking of the detector. Anysolid object which is likely to move may wellcause a false alarm, although some detectorsmay filter out typical patterns of disturbancecause by such incidences as a small sign slightlyswaying in a draught. Ultrasonic detectors donot penetrate glass, timber or masonry.

Normal statutorily controlled broadcastingsystems are very unlikely to cause an ultrasonicdetector to activate an alarm. Exceptionally,unauthorised transmitting or faulty transmittersmay radiate low frequency radio waves creatinga false alarm hazard. Ultrasonic detectors, sitedclose to poorly suppressed electrical orelectronic equipment, may also carry a similarrisk. Unfortunately radio frequency interferenceis difficult to foresee but should be consideredwhen investigating successive false alarms.

ConEnAssoning notes

101. The installer should aim to adjust thesensitivity control to suit conditions applicable tothe periods of unoccupancy when the alarm systemwill be active. In conjunction with this,environmental factors, temperature, humidity andair movement are most relevant. Where theseconditions cannot be simulated the engineer shoulduse his best judgement to compensate the setting ofthe sensitivity adjuster. Proprietary testers areavailable to check for the presence of unwantedultrasonic sound.

102. Under conditions of motionless air and alsolow humidity, which may occur most frequentlyduring periods of unoccupancy, the range of theultrasonic detector may become extended thuscreating the risk of alarms being activated bymotion occurring at a greater distance thanappreciated during walk testing at commissioning.Ultrasonic detectors are most sensitive to radial(towards or away) movement, and should bepositioned with this in mind.

103. Refer to commissioning detailed in section 4.

104. Figure 2 illustrates typical patterns ofcoverage but the shape of the space under protection

3 6

may sometimes slightly widen or elongate theactual pattern of coverage.

MICROWAVE 'VOLUMETRIC'DETECTORS

Theoyy e opezEton

105. Microwave detectors, as the name implies,use low power microwaves to detect the presence ofan intruder. The basic principle of operation may becompared with that of the ultrasonic detector. Themain difference being that ultrasonic detectors relyupon air as the medium to carry the ultrasonicsound wave, whereas the propagation of the electro-magnetic wave produced by the microwave detectoris independent of air. Consequently, theenvironmental factors such as air turbulence,temperature and humidity do not directly affect themicrowave detector. Unfortunately, since themicrowave is inherently a radio signal, there arecertain adverse aspects associated with themicrowave movement detector.

106. The relatively high rate of false alarmsattributed to the microwave detector is generallydue to the device responding to events outside thedesired field of coverage. The detector is notunreliable in itself but its poor reputation stemsfrom it being sited in unsuitable locations orincorrectly set in a too sensitive operating mode.However, modern detectors, incorporatingmicroprocessor technology have a reasonable degreeof immunity to false alarms and may well have auseful role in those applications not suited topassive infrared or ultrasonic devices. The designershould not therefore disregard the existence of themicrowave detector.

107. Indeed, in certain environmental conditions,they may be the only workable form of movementdetection. Most types of detector need to bespecified to be compatible with their operatingenvironment, and none more so than the microwavedevice.

108. Whilst there is no evidence that exposure tovery low levels of microwave energy constitutes ahealth risk, it may be prudent to avoid sitingdetectors close to persons in spaces of sustainedoccupancy. Alternatively some control systems canswitch off detectors during the occupancy periods.

109. Microwave 'volumetric' movement detectorsperform three main functions.

E Transmit a beamed microwave signal into thespace under protection.

29

O Receive microwave signals reflected back from'mass' within the protected space.

Electronically process the received microwavesignal using the transmitted signal as areference. This method relies upon DopplerEffect which occurs when some of the receivedsignal has been reflected off a moving object.

110. Modern microwave detectors incorporatingprocessing circuitry, usually in the form ofintegrated circuits, hold considerable advantagesover their less technically sophisticated predecessorsthat were condemned as a source of false alarms.However, microwave devices have less tolerance tomisuse and adverse environments, accordinglyexpert knowledge is needed to select the rightdetector for the right job. These notes are intendedto assist, but they should be read in conjunctionwith the technical specification of any proposedmicrowave detector.

Requirements for microwavedetectors

111. Microwave detectors should meet thefollowing requirements:

Operate in the microwave frequency band widthat a particular frequency which satisfies localregulations. For the United Kingdom thisfrequency is currently 10.687 kHz.

The transmitted pattern of coverage as detailedin the manufacturer's polar plot, to becompatible with the dimensions of the volumeof space under protection. Normally, optionsexist regarding length of range and shape ofbeam. For long range detectors, the microwaveenergy is generally "focused" in a thin pencil-like beam, whilst short and medium range areavailable with a wide angle projected beam, of15 metres to 30 metres range.

Operate under the Doppler Effect, employingprocessing circuitry to detect frequencydifferences between the transmitted signal andthe received signal and employ further stages ofprocessing circuitry to discriminate betweenDoppler Effect due to a "human intruder" andthat caused by random factors such as smallobjects swaying in a draught.

Incorporate a high degree of immunity to radiofrequency interference. Physical screening maybe provided by the detector's casing.

LI Include a supply voltage regulator, withfiltering against transient and other lineinterference.

LI Be fitted with an easy-to-use range adjustment.A separate sensitivity control is advantageous.

30

LI Include tamper connections to signal a warningwhen the detector cover is removed or when thedetector has become physically damaged. Thecover to be screw fixed.

E Be protected against the ingress of dust, smallinsects and moisture

E Be normally capable of operating in atemperature range of: 10°C to +50°C.

E For installation where more than one microwavedetector is likely to be used, detectors shouldinclude mutual interference immunity circuits.Ensure that fields of coverage do not overlap. Inparticular direction of coverage should beparallel.

[7] LED walk test indicator light to be fitted witha facility to provide an option for it to beremotely extinguished during periods ofbuilding occupancy. Note: this preventsbuilding occupants testing the range ofdetection.

CI) Incorporate a "latch on" facility for the LED. Inconjunction with a compatible control panel theLED will indicate the detector that initiated analarm or responded to a fault condition.

LI Incorporate a facility for the alarm relay to beremotely disabled whilst the control panel is inthe occupancy mode. This significantly reduceswear to the alarm relay. A similar facility toswitch off the microwave transmitter isadvantageous, particularly when it is desired,for any reason, to prevent occupants beingsubjected to low levels of microwave energyradiation.

LI Include self monitoring circuitry to warn ofpending detector fault, or masking of detector.Also to advise "near alarm" occurrence. Thesefeatures should be signalled by a separateoutput and can be used to advantage with"intelligent" and other compatible controlpanels. In conjunction with this output thedetector LED should illuminate when thecontrol panel is in the test or the normaldaytime occupancy mode. Exact arrangementwill depend upon the specification of thecontrol panel used in this application.

LI Incorporate the facility to enable remote testingfrom the control panel or a distant centralstation.

Envkronme=6. fe.=zs

112. For microwave detectors, environmentalcompatibility is extremely important. Althoughmicrowave detectors possess some false alarmimmunity to factors such as air turbulence, and

rts

other climatic changes they are, unfortunately,sensitive to less obvious environmental factors, suchas movement behind walls, and radio frequencyinterference.

113. The following list highlights typicalenvironmental factors which may adversely affectthe operation of microwave detectors:

Microwave detectors can "see" through glass,timber, lightweight building blocks andplaster. Hence "out of sight" movement behindseemingly solid screens may activate a falsealarm. (Adjust range to fall short of walls wherefalse alarm risks exist.) Even air ducts maycarry detection into adjacent areas. (Avoiddirecting detector at external walls, doors andwindows.)

E Mirrors and all metallic surfaces will reflectmicrowaves and may create unexpected newareas of detection, leading to false alarms.(Avoid directing beams at filing cabinets andother metallic objects.) Metallic objects alsocreate a shadow in the field of coverage whereintruders may pass undetected.

The detector should be suited to its mountingposition, either wall, ceiling or corner fixed.The detector must be positioned to detectmovement, by the intruder, that ispredominantly towards or away from thedetector. Microwave detectors have far lessresponse to movement across the field ofcoverage, this is due to the reduced DopplerEffect created by transverse motion.

Microwave detectors may be hidden behindlightweight building materials. Whereoccupancy vandalism is a consideration,detectors may be employed to 'look through'ceilings and partition walls. In that applicationit is essential to ensure that plasterboard is notbacked by aluminium foil.

Small animals, even fish in an aquarium, mayactivate a false alarm.

Vibration is a major source of false alarms. (Fixdetector to a solid structure.) Partition walls

38

10/30mFig. 3 Typical microwave volumetric coveragepattern in free space. Separate units are madewith ranges between 10m and 30m.

and some ceilings may vibrate from the effectsof traffic, aircraft or thunder.

Avoid installing microwave detectors directlyunderneath flight paths where high levels ofaviation noise may exist. Circumstances mayalso arise whereby aircraft navigation aidsactivate microwave devices.

Set range and adjust detector such that it willnot "look through" materials and activate falsealarms due to: heavy rain, hail; or birds on aroof. Also water passing through non-metallicpipes may activate a false alarm.

LI Do not permit objects subjected to draughtmovement to fall within the detector's range.The slightest movement of an aluminiumvenetian blind will activate a false alarm.Suspended signs constitute a similar risk.

E When in use fluorescent and other electricaldischarge lights may activate a false alarm.

LI The range of detection may be modifiedaccording to the use of the space underprotection. Furniture and other physical objectsintroduced to the protected space will create theneed for walk testing to be repeated.Accordingly, readjustment to range or siting ofthe detector may be necessary.

Electrical equipment, particularly rotatingmachinery, and also certain mobile radiotransmissions, may activate false alarms.

Coa-nznissoming notes

114. The importance of walk testing cannot beoverstated. Ensure that movement within the wholeof the space intended to be protected will activatean alarm condition. Also walk test behind closeddoors and walls to verify that the detector will not

3 1

activate an alarm from motion within a legitimatelyoccupied area. Similarly, as far as is practicable,check for false alarms arising from environmentalfactors such as passing vehicles, fluorescentlighting, and water flowing in pipes.

115. Proprietary testers are a useful aid to settingrange and identifying the presence of radiofrequency interference. In respect of this ensure thatthe signal to noise ratio is compatible to thedetector's specification and operating parameters.

116. Adjust the range control to the absoluteminimum setting that is necessary to extend thefield of coverage adequately into the desired area ofprotection.

117. Refer to commissioning as detailed withinsection 4.

118. Figure 3 illustrates the typical free spacepattern of coverage of the microwave detector.Physical objects may distort patterns of coverage.

PASSIVE INFRARED DETECTORS

Theory of operation

119. Passive infrared (PIR) detectors work bysensing an intruder's body heat. In this sense PIRdetectors are not movement detectors. They aresensors of infrared radiation. However, speciallydesigned optics and circuit processing enable thedevice to respond to movement by reacting tochanges in infrared radiation, brought about bymovement of the intruder within the volume ofspace under protection.

120. PIR detectors have 5 main parts.

Sensors (detectors of infrared energy)

121. These are pyroelectric devices, which absorbheat from the infrared rays directed on them. Thisproduces a voltage output that is subsequently usedto operate the alarm relay.

122. Recently, dual element infrared detectors havebeen produced. These comprise a single enclosure,about the size of an aspirin, housing two separatesensor elements. Looking to the future it seemsprobable that multi-element sensors units willsucceed the two-element unit. With detectorscontaining two or more sensors, greater false alarmimmunity can be achieved. 'Quad' detectorsnormally employ two dual element sensors, toprovide four element sections.

32

Optical filters

123. The infrared energy emitted by the humanbody and objects at room temperature fall withinthe spectrum range of 7-14 micro metreswavelength. Accordingly filters are selected totransmit this particular spectrum only and thusform a barrier to other infrared energy frequenciesproduced by environmental factors and therebyeliminating certain false alarm hazards. In theearlier passive infrared detectors the filter formed aseparate component but this is now generally to befound as a component part of the hermeticallysealed sensor device.

Optical (lens and mirrors)

124. The optics of a detector determines the field ofcoverage and the number of sensitive zones.Essentially, the optics direct the infrared energyfrom the field of coverage onto the heads of thesensor elements. The quality of the optics has adirect bearing on the signal to noise ratio of theelectronic signal output and is particularlyimportant in the case of long-range applications.Main types of optics are parabolic mirrors andFresnel lens for single zone detectors and multi-parabolic mirrors and complex Fresnel lens formulti-zone applications. Generally the Fresnel lensis a composite part of the front cover making itvulnerable to deliberate damage. Dust may alsoaccumulate on the lens. Detectors employing theFresnel lens are best used in applications servingsmall areas where the risk of physical damage isnegligible.

125. Lenses employing highly reflective mirrorsprovide a precision optical field of coverage and arehighly efficient at directing the infrared energy onto a sensor head. A further optical refinementcompensates for size and distance of the target,thereby reducing false alarm risks from insects androdents at close range whilst at the same timegiving good sensitivity at the periphery of the fieldof coverage to human size targets. In effect, a targetof a given size will cause the same infrared changeimposed upon the sensor head whether the target isin the near or distant area of the field of coverage.

Case and Lens Cover

126. Many passive infrared detectors have flimsycovers which have little resistance to damageinduced by the opportunist vandal who may onlyneed apply finger pressure to sustain damage.However considerably more durable materials areavailable and quality detectors can be obtained withimproved resistance to wanton damage. Dome-shaped ceiling-mounted detectors offer improved

resistance to physical damage. Covers should besecurely fixed to their base and not rely upon plasticclips .

Electronic circuitry

127. There are more manufacturers of passiveinfrared detectors than any other form of movementsensor. Advances in electronic circuit technologyand competition between manufacturers has led todifferent patented techniques being used to producehighly sensitive detectors with enhanced immunityto false alarms.

128. For difficult environments sensors with "quad"or double dual element methods have specialadvantages. In this type of detector any change ininfrared radiation that simultaneously falls upon allsensor elements will normally be disregarded as ofenvironmental origin and prevented from causing afalse alarm. Only when the sequence and amplitudeof received infrared radiation imposed upon theelements is typical of that induced by intrudermotion, will an alarm be activated by the circuitry.Further false alarm immunity can be achieved bycircuitry which is designed to sense two or maybethree intruder motion signals within a definedperiod, say 20 seconds. Only when this conditionhas been satisfied will an alarm signal be activated.With such a large variety of PIR detectors on themarket it should be possible to select a detector tosuit any given situation.

Requirements for passive infrareddetectors

129. PIR detectors should generally meet thefollowing requirements:

The detector should comply with BS 4737: Part3, Section 3.7.

Operate by sensing a rapid change in levels ofinfrared energy emitted from the field ofcoverage.

Possess an optical lens of adequate quality witheither highly reflective mirrors or wheresuitable, Fresnel lens.

The optical arrangement must produce thedesired field of coverage.

Incorporate an optical filter to transmit only the7-14 micro metre wavelengths.

Possess electronic circuit processing todiscriminate between real and false alarmconditions. Sensitivity to real alarms not to betoo compromised by false alarm immunity.

4 0

An LED to be provided to facilitate walktesting. Means to be provided to eitherextinguish or hide from view the LED toprevent building occupants gaining knowledgeof field of coverage. Some detectors utilise anLED to indicate unacceptably high levels ofbackground disturbance as an aid tocommissioning.

A socket should, preferably, be provided on thedetector to accept a plug from a hand-heldtester. Such testers are available to assist in thecommissioning and setting of sensitivitycontrols.

Detectors should not be used within areas lessthan 60% of their range if environmental falsealarms are to be avoided.

Detectors with automatic temperaturesensitivity adjustment can be used to advantagein environments of considerable temperaturevariation, particularly where high Summertemperatures occur. Generally, there must be a2°C temperature difference between backgroundand intruder body temperature for the device tooperate reliably.

Detectors should be capable of satisfactoryoperation under the following environmentalconditions:

Temperature: 10°C to + 40°C.Relative humidity: 10% to 90%

Self monitoring anti-blind PIR detectors,utilising their own infrared source to monitor,can considerably improve levels of security inhigh risk areas when used with compatiblecontrol panels. They are complementary to theother types of detector produced for use with'intelligent' control panels.

Detectors should incorporate terminals for atamper circuit. This should activate an alarm ifthe detector is physically damaged or if itscover is removed.

Where risks of physical damage exist, selectdetectors of a robust design. There is greatvariation in the physical strength of variousdetectors on the market. Covers secured by alocking screw are generally more effective thanplastic clips. Ceiling mounted detectors are lesslikely to be vandalised or masked.

Traditional PIR detectors.

130. Designed for wall, corner or sometimesceiling-mounted, the field of coverage varies from

33

Fig. 4 Wall mounted PIR detectors for general applications.

1111111_a

Lowplane

Mediumplane

1.5m 30m

Typical plan of long range coverage pattern.

1

High plane

2.5m

60m

34

Typical side view of long range coverage pattern.

L 41

2.3m

Mediumplane

High plane

5m 7m 10m 12m 15m

Typical plan view of wide angle coverage pattern.

15m

5m 7m 10m 12m 15/20m

Typical side view of wide angle coverage pattern.

4 235

4

al

I . -

t 2,

I

o

v. .; *-47;:orXer,-.;re.-91:-./FP7.011";411'er;44:':Nlicr.l*trqr%::,7,517,i;.:,es-

o

0 0 . 0' 0 .0' 0. -

Plan view of full curtain protection.

0.5m

tiir ".- .- - - .: "ir ,00 -0 0 .0 - -0 - - -t_1:. T.!"0.t, "...--gelPe;, ,, ...ye.... .c. ors/1:,;::-..0. v...4010%.-;40:::

Side view of full curtain protection.

4 4 37

Curtain of protection across windows and corridor.They are often used parallel to school computer room windows.

Long range curtain detector used in corridor application, positioned to detect transverse movement.

38

BESTCOPYAVAILABLE4 b

10m, wide angle, to 50m or greater, narrow anglelong range detectors. The field of coverage isgenerally radial from the detector with sensitivezones emanating from the floor close to the detectorand cast at intermediate coordinates rising to a zonecast at a height of about 21 m, towards theperimeter of the field of coverage. In general thesedetectors are intended to be wall-mounted at aheight of 2.5 to 3.5m.

131. A variation of this type of detector comes inthe form of a dome-shaped circular detector. It isintended for ceiling-mounting and the field ofcoverage may be variable and is therefore lessobvious to the intruder, compared with the moretraditional wall-mounted detector.

Curtain detectors

132. The optical arrangement of this type ofdetector produces a field of coverage that is uniqueto the PIR device. It cannot be emulated by themicrowave or ultrasonic detector. The field ofcoverage produces the effect of an invisible wall ofprotection. The zones being cast directly above eachother. The advantage of the curtain detector is itssuitability to specific applications. The device maybe used for example, to cast floor to ceilingprotection immediately parallel to a large glazedarea. Mounted at 900 the device may be used tocast a thin field of protection directly below aceiling containing roof lights which could be apossible means of access to an intruder.

133. Since the invisible wall of protection can beaimed very selectively into the target area it isfrequently possible to provide excellent levels ofprotection with unwanted environmental fact6rslying outside the field of view. False alarm risks arethus minimised. Generally, full curtain detectorshave a maximum range of approximately 10m.Recently introduced long range models extend toabout 45m but high level protection reducestowards the extremity of the range.

Ceiling-mounted detectors

134. Similar to PIR wall-mounted detectors, theceiling mounted detector can be used in schools forwide angle, curtain or long range protection.Additionally, detectors are available that produce acomplete 360° symmetrical field of coverage,making them ideally suited for use in assemblyhalls and other open areas where they may bepositioned directlyabove target items. Althoughgenerally intended to be used with an all-roundfield of coverage of 360°, segments may be maskedto screen specific environmental factors.

4 6

135. Being fabricated from relatively robustmaterials in the shape of a dome, they offerimproved levels of vandal resistance. Similarly,ceiling mounting may often place them out of thevandal's reach. By means of a special bezel the unitsmay be flush mounted into suspended ceilings,combining the benefits of a neat and discreetappearance with improved physical protection.

136. Ceiling-mounted detectors have a particularadvantage in spaces liable to have furniture placedaround the walls which may otherwise mask wall-mounted detectors. Also, being spherical inappearance it is difficult for the intruder toanticipate the field of coverage.

Environmental factors

137. Compared with microwave and ultrasonicdevices PIR detectors have a greater basic immunityto most random environmental factors. Thefundamental principle of operation of the PIRdetector, in its basic form, is less sensitive tomovement and random environmental factors thanmicrowave or ultrasonic methods of detection.Noise and vibration cause very little problem. Alsothe range of coverage will not penetrate glass orother common building materials. The followingenvironmental factors could effect the operation ofPIR detectors:

0 Temperature

138. At approximately 30°C PIR detectors becomeinsensitive to intruder movement. At thistemperature infrared energy radiated by a human isvery similar to background radiation andaccordingly the device cannot perceive themovements of a human. PIR detectors incorporatingtemperature compensation simply set the device tomaximum sensitivity at human body surfacetemperature. Set in this mode of maximumsensitivity the device is assisted in its detection ofhuman movements by the fact that different parts ofthe human body have slightly different surfacetemperatures. However there still needs to be atemperature differential of at least 2°C to beconfident of movement detection.

0 Relative humidity.

139. PIR detectors have a good tolerance tohumidity variation. In fact, the principle ofoperation is virtually unaffected by humidity.However at relative humidity below 10% andabove 90% problems are likely to occur. This isprimarily due to the reactions of the processingcircuitry where lack of humidity may allow static

39

Fig. 6. Ceiling mounted PIR detectors

floor

15° 0° 15°

Plan view of full 3600 coverage pattern.

detectorceiling

10.m

Side view of 360° coverage pattern.

40 4 7

2.5m

.0m

Om

detector

Plan view of wide angle coverage pattern.

16m

ceiling 4-2.4m

fp: 41-0.16;47.--X4-1.:-:,iti: ii74TotTo7i;4AT,Z0:::.:WIt.;40:10i0;41.1niz.*:-. 6::;;;;;:,"4::;;;;;. ,..,;;;spip-,;;;"4---...-z!vo:"*.:17;-"-Vier---":717;;;;;; 07::- !fie1 R; OA"' °01.

16m

Side view of wide angle coverage pattern.

4 84 1

floor

(Figure 6 continued)

8.0m

8.0m

22m

Plan view of wide angle, longer range coverage pattern.

detector

2.4

ceiling

42

''':!;;.?141,1fis;:f7:::::.?"-tr;*-7:Fa'r%,.

22m

Side view of wide angle, longer range coverage pattern.

S. 4 9

floor

5.0m

5.0m

detector

Plan view of long range coverage pattern.

Side view of long range coverage pattern.

Plan view of vertical curtain lorig range coverage pattern.

detector

ITieg;'"W:::7*A"g ;WV 1.°!

Side view of vertical curtain long range coverage pattern.

5 043

Isometric view of wide angle coverage pattern.

44

View of curtain type coverage pattern.

51

electricity to build up and high levels of humiditymay cause moisture to have an effect on theprocessing circuitry.

140. The optics of the device will become obscuredif condensation forms upon the lens or the lenscover.

O Air motion.

141. PIR detectors are not directly affected by airmovement. However if air strikes the surface of anobject within the field of view, causing a suddenslight change of surface temperature, a false alarmmay be activated. Similarly air movement directlyupon the detector may cause an alarm condition.Also glass windows may sustain a small, but rapidchange in temperature due to beams of sunlightbeing broken by swaying trees.

O Light.

142. Variation in ambient lighting levels isunlikely to activate a PIR detector. However,Tungsten halogen floodlighting and car headlightscan impose a temperature change upon the sensorthat may activate an alarm if directed into the lensof a detector. Detectors with inadequate false alarmimmunity may be activated by ordinary tungstenlight bulbs.

143. Sunlight may also activate a false alarm whenit penetrates directly into the detector. At certaintimes of the year the sun appears very low in thesky and may easily penetrate through a window andinto the lens of a detector. In exceptionalcircumstances sunlight may be reflected from apolished floor and into a detector since generally thezones of protection radiate from the detector at anangle towards the floor. Dual element, or quad,detectors have good immunity to light activatedfalse alarms, and are suited for sch000l applicationsparticularly where glazing is extensive.

O Heaters and radiators.

144. Avoid directing the detector at any source ofheat. There have been many false alarm activationscaused by heaters switching on automatically priorto building occupancy. In some instances the airturbulence created by heat can cause objects tomove thereby producing a change in backgroundradiation which may possibly produce a false alarm.Christmas decorations and hanging mobiles aretypical examples.

0 Insecticides

145. Ensure that the detector is positioned to avoidthe lens or cover being sprayed by liquid fly killeror other insecticides.

0 Physical objects

146. The PIR detector's zones of protection do notpenetrate glass or other physical objects.Accordingly such objects may form a barrier behindwhich an intruder may pass undetected. However,in practice, with optical lenses producing a densepattern of coverage, it would be extremely difficultfor an intruder to pass between solid objects withinthe field of coverage without the alarm activating.

Commissioning notes

147. Unlike microwave or ultrasonic detectors theearly PIR devices were not fitted with a sensitivityadjustment. Since glass and other building materialsform an impervious barrier to the range of a PIRdetector sensitivity is not an importantconsideration when determining the effects ofexternal environmental factors. However, some ofthe much more sensitive modern PIR detectors havea sensitivity adjustment and this must be carefullyset so as to be in harmony with its environment. Ifthe detector is set too sensitive it may activate inresponse to a cool draught, slightly cooling thesurface of an object within the field of coverage.Conversely, lack of sensitivity may permit a carefulintruder to pass undetected. An apt tradeexpression, refers to PIR detectors as "going tosleep" in warm environments. Accordingly, whenwalk testing to check sensitivity levels, it must berealised that the device will probably be far moresensitive on a cold winter's night than on a hotsummer's afternoon. Hence the actualcommissioning environment must be compared withthe variances of actual operating conditions whenthe setting of the sensitivity control is determined.Some detectors have the advantage of mobile opticsthat can be moved into position to enable thepattern of coverage to be confirmed by displaying alight that is only visible from points within thefield of coverage.

148. Proprietary test meters may aid setting ofsensitivity. Also some detectors incorporate an LEDcircuit that indicates high levels of backgrounddisturbance necessitating a reduced sensitivityadjustment. As a rule of thumb, backgrounddisturbance should not account for more than 30%of the alarm threshold value.

149. Heating, ventilation and lighting is often

45

automatically controlled and may come on prior tobuilding occupancy. This results in rapidenvironmental changes which could create a falsealarm condition. Where possible such adverseenvironmental conditions should be simulatedduring commissioning. Failing this, sensitivitycontrols should be set to compensate wherepossible.

150. Refer to commissioning as detailed withinsection 4.

151. Figures 4, 5 and 6 illustrate coverage patternsfor the various types of PIR detectors.

DUAL TECHNOLOGY DETECTORS

152. These movement detectors contain twoseparate, interconnected, devices within the samehousing. A PIR device is normally combined withanother device such as an ultrasonic or microwavemovement sensor.

153. Dual technology detectors are primarilyintended for use in environments where occasionalhigh levels of background environmentaldisturbance constitute an exceptional false alarmrisk. Before an alarm signal can be activated both ofthe two separate technology devices must sense analarm condition, either simultaneously or within adefined time lapse. Since PIR devices respond totemperature change occurring due to the motion ofan intruder and both microwave and ultrasonicdevices respond to actual physical motion, the twoseparate technologies have different sensitivity levelsto different environmental disturbances.Consequently, random factors that may activate onetechnology will not stimulate the other technology.For example, fast moving headlights may activate aPIR device, but neither ultrasonic or microwavetechnology will sense the presence of any motion,accordingly a false alarm will not be activated.

154. Since two separate technologies are used in acombined detector both of these can be used in ahighly sensitive mode. By way of an illustration, abasic stand alone microwave detector may seek adoppler frequency shift of approximately 100 hertzor more which equates to walking speed, whilstwhen this device is employed as one of thetechnologies of a dual technology combination, themicrowave sensor may be designed to produce analarm condition for a doppler frequency as low as10 hertz. Although such a high level of microwavesensitivity could be highly reactive to randomenvironmental factors, it is very unlikely that thesame random factors would cause the PIR device to

46

activate, accordingly a false alarm would not arise.

155. Two types of dual technology detectors arecommonly available. Either the PIR combined withan ultrasonic detector or a PIR combined with amicrowave detector.

156. In comparison to the PIR/microwavecombination, the PIR/ultrasonic arrangement has agreater coincidence of susceptibility to commonenvironmental disturbances, resulting in a higherfalse alarm risk. In practice, however, thiscombination can be used to excellent effect in mostdifficult environments. The coincidence of both PIRand ultrasonic technologies simultaneouslyproducing a false alarm can be virtually eliminatedby employing a PIR section incorporating doubleelement or "quad" sensor arrangements, backed upby high levels of circuit processing.

157. The adoption of two separate devices ofdifferent technology greatly increases the componentparts of the device. Accordingly the likelihood ofthe detector failing, particularly the activecomponents, is considerably more probable than inthe case of the single technology device. A separatewalk test light should confirm the operation of eachtechnology. Ideally, another light will indicatewhen a pre set ratio in the number of activations ofeach technology is exceeded during the disarmedperiod, thereby giving early warning of one devicebeing either over or under sensitive.

158. In view of the advances that have beenincorporated in stand alone PIR and also ultrasonicdetectors to achieve high levels of fales alarmimmunity, the viability of using the more expensivedual technology devices needs to be carefullyanalysed. There is a strong opinion that singletechnology offers higher levels of security than dualtechnology. However in the most adverseenvironmental conditions, dual technology detectorshave a valuable role to play. Lightweight buildingssuch as portable classrooms situated in exposedlocations are just one possible application. Evendual technology devices have their limitations, in anextremely adverse environment at least onetechnology is likely to be in an almost permanentalarm mode thereby reducing the device to that ofsingle technology.

159. Dual technology detectors generally impose agreater electrical current demand on the alarmsystem and as a consequence this increases thevoltage drop on cable runs. When a dualtechnology detector is used to replace a singletechnology detector because of persistent false alarmactivation, care should be taken that any additionalcurrent demand imposed upon the system will notgive rise to an unacceptable increase in voltagedrop.

5 3

160. The PIR/ultrasonic combination generally hasa broad pattern of coverage extending up to amaximum of about 10m. PIR/microwavecombinations have various options regarding thefield of coverage, including long range to a distanceof approximately 60m.

161. As a rule of thumb, dual technology detectorsare approximately 2-2-1- times more expensive thansingle technology devices.

162. To more fully appreciate the nature of dualtechnology detectors it is necessary to gain anunderstanding of each of the separate technologiesof PIR, ultrasonic, and microwave. Beforespecifying any particular dual technology detector,careful attention should be given to themanufacturer's performance specification,particularly with regard to levels of sensitivity.

163. A guide to detector requirements andenvironmental considerations may be assessed fromthe descriptive text herein regarding each of theseparate technologies.

164. Walk testing assumes a p6sition of primeimportance with dual technology detectors. It isimportant to create motion separately in radial andlateral directions through the entire field ofcoverage, both in close proximity and also at theedge of the intended field of coverage. An alarm

Flat PVCenvelope.

4C

should be activated in all areas of the required fieldof coverage by motion typical of that created by aslowly moving, cautious intruder. Figure 7illustrates typical coverage patterns for dualtechnology detectors.

SELF-MONITORING DETECTORS

165. At the date of this publication, detectormanufacturers are seeking to produce a full range ofself-monitoring detectors. Active detectors, such asthe ultrasonic device, lend themselves to this self-monitoring function since the device inherentlymonitors its own self-generated signal. To simulatethis principle in the PIR detector an active infraredtransmitter is added, for producing an infrared aurafor the passive sensor to monitor. Protection is alsoprovided against attempts to 'blind' the PIR sensor.

PRESSURE MATS

166. Pressure mats are intended to be hidden undercarpets and will activate an alarm when subjected tofoot pressure. They are manufactured in a largerange of sizes with the smallest 150mm by 600mmmat intended for insertion under a stair carpet.

Fig. 8 Typical pressure mat.

NEMIli!11111 tli.1,1

2 leads for alarm circuitkg\ 2 leads for tamper circuit

40cm typical.

5 4

20cmflatypical.

V

47

2.4m

Fig. 7 Dual technology detectors.

W-- "iOP j. "a'..T.,..:41VF'00;0'7 .01 1.7 ,V411111 rer,..-;,-.1,:, ..7,,,t, -. 0._e dr, . :Ate, -

Typical plan view of long range coverage pattern.

ss.

3/5m

48

10/60m

Typical side view of long range coverage pattern.

Microwave 'balloon'type volumetriccoverage.

Zones of infraredK\werage pattern.

2.4m

10/30m

Typical plan view of wide angle coverage pattern.

Alarm signalled whenboth microwave andinfrared patterns sensemotion simultaneously

10/20m

17'.1.0:;;-;:;:-!",t-4f;14%,`;*1.11V-ife:i.vke..7e4:

10/30m

Typical side view of wide angle coverage pattern.

Note: Ranges vary according to different manufacturers models.

495 6

Modern pressure mats consist of a very thin PVCenvelope containing a sandwich arrangement of twothin metallic foil sheets separated by a thin sheet offoam rubber. A pattern of holes in the foam permitsthe foil sheets to establish an electrical contactunder foot pressure. The foam is sufficiently spongyto separate the contacts upon release of footpressure.

167. Protruding from the envelope are four fly leadconnections. Two are connected to the metallic foilsheet and carry the alarm signal. The remainingtwo leads form the ends of a continuous wiring loopwithin the PVC envelope. Since the foot pressure ofan intruder is used to "make" an electrical contact,pressure mats have a security weakness since underfault conditions the mat could fail permanently inthe "non-alarm" mode. Accordingly regular testingis essential, particularly where mats are placed inareas with heavy foot traffic during periods ofnormal occupancy.

168. The pressure mat needs to be carefullyconcealed under the carpet to be completelyunobtrusive and at the same time strategicallyplaced for maximum likelihood of trapping theintruder. If this criterion can be fully met with themat positioned in an area away from normaloccupancy foot traffic, there is the added advantageof less physical wear upon the pressure mat and lesslikelihood of the mat outline becomingdistinguishable from above the carpet. Pressuremats are not intended to be installed beneath plasticfloor coverings.

169. Dampness can have an extremely adverseeffect. If moisture penetrates inside a pressure matthere is a likelihood of false alarms or of a failure torepond to alarms situations. Avoid siting pressuremats where footwear may deposit rain water orsnow.

170. Figure 8 shows a typical flat PVC envelopetype pressure mat, with fly leads for protective andtamper connections.

171. In determining the location of a pressure matconsideration must be given to the proposed cablewiring route. With this in mind there is anadvantage in siting the mat close to a wall ordoorway where the cable can subsequently be routedto an adjacent wall and thereby concealed from.view.

172. At the date of this publication pressure matsmay be purchased for less than £2. With thegreater availability of reliable electronic movementdetection there has been a decline in the use ofpressure mats. They have limited scope for schoolapplications.

50

173. Further requirements for pressure mats aredetailed in BS 4737: Part 3

PROTECTIVE SWITCHES

174. Protective switches are normally concealed indoors and window frames and activate an alarm,when a magnet fixed to the top of the door orwindow is moved due to the opening of the door orwindow. With a purchase price of less than £2 theyoffer a reliable cost-effective form of protection.With determined effort they can sometimes bedisabled and accordingly protective switches cannotnormally be regarded as high security devices.However they adequately meet the needs of mostschool building applications. In trade literature theymay be referred to as magnetic reed contacts (MRC)devices.

175. Protective switches have had a long history insecurity applications and a number of technicalvariations have evolved. However for all practicalpurposes the present industry standard can beregarded as the magnetic contact protective switch.The simplicity of this device provides long-termreliability without false alarms. However this is notachievable when poor quality protective switches areemployed or standards of installation practice areinadequate.

Design and operation of protectiveswitches

176. Two types of protective switch are commonlyavailable, either concealed or surface fixed, themode of operation is identical. At the heart of thedevice is a reed switch consisting of two springy,reed-like wires, having contacts at their ends.Under the influence of a magnet the contacts can bemade to touch or separate, thus activating an alarmwhen a magnet fixed in a door or window ismoved. To reduce contact resistance the reed switchcontacts should be plated in Rhodium or silver.Degradation of the switch is further reduced byencapsulating the reed assembly in an airtightenvelope which is subsequently pressurised with aninert gas. Finally the device is enclosed in aprotective plastic or aluminium enclosure. The useof separate ferrous metal screening around theprotective switch can be used to combat attempts todisable the device by placing a magnet close to theprotective switch.

177. In the most likely application, the.protectiveswitch will be installed in the top member of adoor frame. In conjunction with this a permanent

,.. 5 7

magnet will be concealed into the top of the doorhead coordinated to marry up to the face of theprotective switch when the door is in the closedposition. Under the influence of the magnetic fieldthe alarm contact reeds are held together forming aclosed circuit. Opening of the door removes themagnetic field allowing the reed contacts to springapart thus producing an open circuit which activatesthe alarm signal. This mode of operation has asecurity advantage since the device is most likely tofail into the alarm condition.

178. To facilitate connections to the alarm systemwiring, the protective switch is provided witheither four terminals or a four-core fly lead. Twoconnections provide the alarm circuit whilst theremaining two are the ends of a tamper loop insidethe switch.

Installation of protective switches

179. The installation must adhere to certain basicrequirements to effect good levels of securitywithout false alarms. A protective switch can be

most effective when it is concealed in a door frameand fully hidden from view. The installer needs toapply skill in cutting the holes and discreetlyconcealing the device together with its associatedwiring. This latter point is particularly importantsince visible wiring can draw attention of anintending intruder to the fact that a door or area isprotected. Whenever possible the wiring should beconcealed, but where any needs to be surface run itshould be on the side least likely to be noticed. Itshould also be adequately protected to minimise thepossibility of anybody tampering with it at anytime.

180. Of prime importance is the relative position ofthe protective switch and its operating magnet.Accurate alignment is most essential. The gapbetween the magnet and the face of the protectiveswitch should not normally exceed 0.5cm exceptwhere a special long gap device is used permitting agap up to 2.5cm. Where an excessive gap exists themagnetic field acting upon the reeds will beweakened and may fail to keep the reeds in contactwhen environmental factors cause slight vibrationsor movement of the door. The protective switch andits associated magnet must be compatible, therefore

Fig. 9 Concealed protective switch typical application.

Connections for alarm andtamper circuits.

Magnetic contact fitted flushin top of door frame.

fPermanent magnet fitted flushin top of door

51

Fig. 10 Surface mounted protective switch typical application.

(Permanent magnet fitted levelwith top of door

Connections for alarm andtamper circuits

,

it is essential that the magnet is matched to theparticular protective switch. Inadequate magneticforce will result in false alarms; conversely too muchmagnetic force may not permit the reeds to separatewhen the door has been opened sufficiently topermit access to an intruder.

181. For schools, the most suitable location for aprotective switch is when it is concealed in the headof a door frame, approximately 200mm distant fromthe hinge side. This will permit draught movementof the door, on its catch, or non-malicious attemptsto open the door without raising a false alarm.However the protective switch will still be sensitiveenough to activate an alarm before an opening ofany significance occurs. Exceptionally where internaldoors are securely aligned in their frames, theprotective switch may advantageously be sitednearer to the opening edge. BS 4737 requires thatthe device operates before the opening exceeds100mm. Any remedial work needed to the doorshould be carried out prior to the alignment of themagnet with the protective switch. For schools it isnot generally recommended to fit protectiveswitches to the vertical members of a door frame.

52

Magnetic contact fitted toinside face of the door framehead

The protective switch would lack sensitivity on thehinge side and present an unacceptable false alarmrisk on the catch side, unless the door is in goodalignment and securely held when locked. It isimportant that any opening fitted with a protectiveswitch incorporates a properly maintained latch orother mechanical device to hold the opening in theclosed position thereby preventing accidental falsealarms. Where locks or bolts are used it isnecessary to ensure that fire regulations are notinfringed.

182. In certain applications, surface-mountedprotective switches are the only option. Often thisapplies to metal doors and windows. To reducerisks of vandal damage and identification by thepotential intruder, surface-mounted devices shouldbe installed in as neat and unobtrusive manner aspossible. Towards this aim, some manufacturersoffer a choice of colour.

183. Protective switches are virtually maintenancefree and have a long life expectancy. Eventually, thereeds may fail or the permanent magnet may grow

1 5 9

weak. Sometimes a loose door hinge or faulty catchwill produce a false alarm.

184. During commissioning, the door or otheropening section should be moved within the limitof its securing mechanism to ensure that an alarmcannot be induced. This is particularly relevantwith metal fixtures since the magnetic field may bereduced in strength. Commissioning tests shouldalso ensure that an opening of 100mm cannot beexceeded before the device operates.

185. Protective switches are manufactured for somespecialist applications including protection to rollershutter doors.

186. Figures 9 and 10 illustrate typical applicationsfor concealed and surface type protective switches.

187. Further requirements for protective switchesare detailed in BS 4737: Part 3:

CONTINUOUS WIRING

188. Continuous wiring, in tubes, is mosteffectively used to protect against intruders gaining

entry through small windows or roof lights. Smalldiameter metal tubes, of a maximum 1 m length,are fixed across the opening at maximum spacingsof 100mm. The system of wiring passed throughthe tubes consists of an interwoven circuitconfiguration of two closed loops. If either loopbreaks, or makes shot circuit contact with the otherloop an alarm is activated. This once commonlyused form of protection has fallen into decline asvolumetric devices have taken precedence. However,continuous wiring in tubes can be effectively usedin many applications and also where volumetricprotection is installed as the main form of intruderdetection.

189. Although inexpensive in material content, thelabour-intensive task of fixing and wiring the tubesmay raise its installation cost to that of volumetricprotection. The most cost-effective applications arewhere small windows or roof lights exist in highlycompartmentalised spaces. Typically, a cateringblock may be constructed with a flat roof andpartitioned into small stores, food preparation,cooking, washing-up, office and corridor spaces.Here, continuous wiring in tubes may be cost-effective in protecting the small stores and otherspaces which typically are provided with smallwindows or roof lights. This form of protection acts

Fig. 11 Continuous wiring in tubes typical application.

100 max.

141-1.0m max.

0

0

Tube and batten frame fitted:"'inside window aperture.

Typical tube and batten frame assembly madeto size of window aperture.

6 0

53

as a visual deterrent to the casual intruder andprovides a signal at the first instant of an attemptedbreak-in. Furthermore, immunity exists against theenvironmental factors that adversely affectvolumetric protection. Unlike volumetric methodsof protection there are no electricity consumingcomponents and advantageously this method ofprotection will not impose a voltage drop on thealarm system wiring. This may be a benefit when itis necessary to economically extend protection to aremote part of a school building, or to any part of asystem that cannot support further electrical loadingwithout supplementary power supplies. Thismethod is relatively accessible and is susceptible tophysical damage, accordingly it is unlikely to beeffective when installed in areas of school pupiloccupancy.

190. Continuous wiring in tubes does not in itselfoffer high levels of security. With effort, it may bedisabled by an intruder possessing knowledge of theelectrical connections. Accordingly volumetric orother forms of protection should be provided toprotect against an intruder penetrating further intothe building.

191. Tubes across windows are generallyaesthetically unacceptable for normally occupiedspaces and in some situations may even obstruct thefire escape route. An alternative similar method ofprotection dispenses with the use of tubes. Thisform of continuous wiring suffers greater exposureto accidental damage and is unlikely to be suitablefor use in schools.

192. Figure 11 shows continuous wiring in tubesmounted to a frame fixed inside a window opening.

193. For further details of continuous wiringprotection refer to BS 4737: Part 3.

FOIL ON GLASS

194. This traditional form of protection consists ofvery thin aluminium or lead tape bonded near tothe edges of a pane of glass. When the glass iscracked or broken the tape will break and activatean alarm. Where two adjacent tapes are applied in adouble pole circuit arrangement, an alarm will alsobe activated if the two tapes make contact witheach other. The tape is specifically manufactured tobreak easily when the glass is broken and to achievethis degree of fragility its maximum permissibledimensions are 0.04mm thick and 12.5mm wide.Consequently the tape has very little resistance to

54

accidental damage and therefore great care must betaken in the installation process. Thoroughpreparation is essential and in respect of this theglass must be clean and free from condensation andgrease. The tape should not be fixed to plastic film.BS 4737: Part 3, details examples of permissiblelocations for foil.

195. One of the most commonly used arrangementsfor normal plate glass application is where themetallic foil tape is bonded as a continuous closedcircuit loop around the perimeter of the glass, withits two ends terminated at a block of terminalsfixed near one corner of the pane of glass. Tocomply with British Standards, the tape must befixed .within a zone 50mm-100mm from the insideedge of the frame. Where higher levels of securityare required or simply to facilitate the wiringinstallation, two tapes may be run in parallelconnected at the terminal block to form twoseparate closed circuits. If either tape is broken, orif the tapes touch, an alarm will be activated.

196. The foil tape should be firmly bonded to theglass as one continuous length, necesSitating thecorners to be carefully folded over, creating a 45°crease. Before the widespread use of self-adhesivealuminium foil tape, this tape was bonded to theglass with varnish and then subsequentlyrevarnished to provide a protective covering. By thesame principle, the self-adhesive aluminium tapeshould be sealed with a top coat of non-corrosivetransparent lacquer. This will guard againstaccidental damage without significantly adding tothe strength of the tape and thereby reducing levelsof security. Most accidental damage emanates fromwindow cleaning activities. It is possible for veryfine breaks to occur in the tape, producing randomfalse alarms as wind, temperature and otherenvironmental factors play upon the glass. Forschools this method of protection is notrecommended for teaching areas or other places ofpupil occupancy.

197. The foil tape must not be applied across joinsor cracks in the glass. Remedial work should beimplemented where the tape becomes detached orblistered. Wired glass, and laminated glass requiremore extensive treatment of foil tape to effectadequate security than that detailed herein for plateglass. This is because it may be possible topenetrate an area of this type of glass whilst stillleaving the perimeter of the glass pane intact.

198. Figure 12 shows a typical arrangement forfixing foil on glass. Examples are based uponrecommendations in British Standard 4737: Part 3:Section 3.2.

Fig. 12 Foil on glass.

100 max.t50 min.

100 max.50 min.

100 max.50 min.

200 max.

100 max.50 min.

300 min.

Typical arrangements for foil on glass. Extractsfrom BS 4737 are reproduced by permission ofBSI. Complete copies of the standard can beobtained from them at Linford Wood, MiltonKeynes, Bucks. MK14 6LE.

6 "455

BREAKING GLASS DETECTORS

199. Breaking glass detectors provide a cost-effective form of point of entry protection. Thereare two types, vibration and acoustic. Vibrationdevices are bonded to the glass and "feel" the highfrequency vibrations, typically 150 kHz, producedwhen the surface of glass shatters. Acousticdetectors work at audible/ultrasonic soundfrequencies and are microphone type devices that"listen" for selected frequency bands of sound thatare generated by breaking glass.

200. For multi-pane application acoustic protectionis likely to be the more cost-effective. Refer to BS4737: Part 3 for further information.

201. The following installation and commissioningnotes are intended to assist in the appropriateselection of vibration and acoustic types of breakingglass detectors.

Vibration breaking glass detectors

Detectors should be fixed close to the edge of apane of glass. A radius of coverage of 2.5m isnormally obtained.

Li] These devices are designed for use on standardfloat glass or plate glass. When used inconjunction with laminated, or toughened glassor where plastic film is applied to the glass, therange of protection will be reduced by at least50%. They should not be used on wired glass.

In order to "feel" the vibrations it is essentialthat the devices are firmly bonded to the glass.Do not attach to any protective plastic filmapplied to the glass.

The detectors should be protected against theingress of condensation. Some manufacturersproduce waterproof, or totally encloseddetectors.

In conjunction with a compatible control panel,these devices may beneficially be connected to a24 hour zone. This will provide a local alarm ifthe glass is broken during periods of occupancy.

To ensure that a faulty detector fails into thealarm mode the device should be of thenormally closed contact type. Connections for atamper circuit must be provided.

The devices will, typically, operate at afrequency of approximately 150 kHz, andincorporate circuit processing to eliminate falsealarms from ultrasound and radio frequencyinterference. Most manufacturers achieve thisrequirement to excellent effect.

56

These devices normally impose a low currentdrain upon the system wiring of approximately10 mA.

E Vibration devices have excellent tolerance tovariations in temperature and may providesatisfactory performance from 30°C to +70°C. Variations in levels of humidity arevirtually irrelevant where the devices areclassified as waterproof.

In a school they may usefully be used to protectshowcases containing valuable items such astrophies. However it is necessary to ensure thatglass is of the standard plate type.

Except where urgent security requirementsprohibit, the device should be tested in use fora minimum period of 7 days prior to itsconnection to a remote signalling system.

Commissioning should be carried out with theaid of a proprietary tester specifically matchedto the vibration detector in use. Such testers areplaced against the glass to impose a vibrationwhich simulates that of breaking glass.

Detectors should be checked regularly as theymay become detached from the glass. Alsointruders may gain access by melting a hole inthe glass, without producing significantvibrations.

202. Figure 13 shows typical locations for sitingvibration breaking glass detectors.

Acoustic breaking glass detectors

Acoustic detectors activate an alarm in responseto the sound of breaking glass. Since they mayoperate in the audible/ultrasound range theyhave a very high natural vulnerability to falsealarms being caused by extraneous sound.However, electronic processing can achieveexcellent immunity to false alarm activation.

Breaking glass produces a very wide frequencyspectrum of sound waves. By analysing thewave form produced by breaking plate glass,circuit processing seeks to recognise a definedsequence of relatively low and high bands offrequency at specific amplitudes. Only whensound is generated through this characteristicformat will an alarm be activated. Furtherdiscrimination is achieved by adding an alarmperiod. Because the breaking process of glassnormally exceeds a period of one second, butlasts less than four seconds, electronicprocessing is used to eliminate signals of lessthan one second duration or greater than fourseconds duration. The process described here is

Fig. 13 Breaking glass (vibration) detector'1,f4

*..*

Typical applications on standard glass.(Range may reduce by 50% on laminated or film protected glass.)

8m

Additional detectors may be added to suit size of glass pane.

4.0m

2.0m

3. m

Door connector trap.

2.5m

Fit a separate detector toeach pane.

6 4

El

1.10m

Glass doors can beprotected.

2.0m

57

typical and manufacturers have developed their ownpatented variations of circuit processing principles.However, the quality of the signal processing willgenerally be reflected in the product price.

LI Acoustic detectors are suitable for protectingstandard plate glass 3-12mm thick but notsuitable for toughened or wired glass.

LI They may generally be ceiling or wall-mountedup to a maximum range of 5m distance fromthe furthest points of glass under protection.

LI They impose a very low current drain upon thesystem wiring.

LI They can be very cost effective for protectingmulti-pane windows, though some acousticdetectors are insensitive to the breakage of verysmall panes.

LI Generally, they possess greater resistance tovandalism than volumetric detectors,particularly when ceiling-mounted.

LI Acoustic detectors should be provided withtamper protection and incorporate a latchingLED as standard.

(11 Being a passive device any number of detectorsmay be used in the same vicinity.

Acoustic detectors should operate within thefollowing environment range.

LI Temperature: 10°C to +50°C

LI Relative humidity: 10% to 90%

LI Environmental factors likely to create falsealarm risks are as follows:

Machinery producing ultrasonic sound

Metal to metal contacts such as letter flaps

Ultrasonic volumetric detector in closeproximity

Jets of compressed air or gas

Cracked or insecure glass

Scratching to the surface of the glass, orglass moving on glazing pins

LI A commissioning test should be carried out.Proprietary testers are available but they aregenerally matched to a particular acousticdevice.

203. Figure 14 shows a typical application foracoustic breaking glass detectors.

Fig. 14 Breaking glass (acoustic) detector. Typical application

Range of detection typically4.0m max. to furthest point ofprotected glass. Preferredrange 2.5/3.0m. Greatestsensitivity when detectorlooks directly at glass.

58

65

Combined technology, breaking glassdetectors

204. These detectors incorporate a vibration devicetogether with an acoustic sensor and both must besensitised to activate an alarm. Unlike singletechnology devices, combined detectors operate inthe lower audible frequency range, typically1-3 kHz. Since there is less attenuation of soundwavelengths at low frequencies, the range ofdetection may be as much as 7.5m. This is partlyachieved by the fact that each technology can beoperated in a highly sensitive mode without seriousrisks of false alarm.

205. The combined technology device must befirmly secured to a part of the building structureclose to, and physically connected to, the windowframe. Similarly the glass must be secure in theframe. The vibration sensor "feels" the vibrationsthat have been produced by the breaking glass andhence transmitted through the building fabric tothe point where the device is fixed to the structure.The airborne soundwaves of the breaking glass aresimultaneously used to activate the acoustic knsor.When both sensors are simultaneously activated analarm signal is produced. Draught excluded orhinged windows may not carry vibrations as well asfixed windows, thereby effectively reducing therange of detection.

206. Combined technology devices have a highimmunity to false alarms, but these activations maystill arise if the glass is subjected to an impactduring a period of high ambient noise. Also,vigorous shaking of metal shutters close to thesiting of the detector may similarly activate analarm.

207. During commissioning the device should betested to ensure that both technologies arefunctional. Two different testers are used, oneproduces a safe impact upon the glass and the other'generates a sound signal. As with all securitydevices regular testing is important. This isparticularly relevant in the case of combinedtechnology devices. In rare situations, it may bepossible for one technology to fall into the non-alarm mode without the building owner beingaware of the loss of security protection.

VIBRATION DETECTORS

208. Vibration detectors are fixed to buildingstructures and high security items such as safes andfiling cabinets. When attempted entry createsvibration of the sensor an alarm is activated. Most

.; 66

vibration detectors are designed to respond tovibrations characteristic of intruder activity whilstignoring vibrations from environmental sources.The detectors are tailored to their specificapplication, which may generally fall into the threecategories: general structures, vaults andstrongrooms; and single items such as safes andcabinets. There are two types of sensor; electro-mechanical or electronic transducer. Both types areconnected to an electronic analyser which may beintegral.or remote from the sensor. The electro-mechanical sensor is generally defined as an inertiadetector. The pure electronic device containing apiezo electric crystal is commonly referred to as aseismic detector.

Vibration detectors for generalapplications

209. Selection of the correct type of device isimperative. Both inertia and seismic devices areavailable. In each type of device manufacturers haveused ingenious patented analytical processingcircuits to discriminate against environmentalvibrations, and accordingly performancespecifications must be in harmony with applicationrequirements. Where desired protection applies tosmall numbers of vulnerable items such as doorsand window frames, detectors with an integralanalyser are most appropriate. Where whole areas ofwalls, ceilings or floors require protection, groupsof up to 8 detectors may be connected to,a single,remote analyser. This method is most frequentlyused in strong room applications. However, forgeneral purpose use, the composite sensor andanalyser arrangement is the most commonly usedform of protection. Vibration detection provides afirst line of defence against intruders. In mostapplications vibration detection is supplementary tovolumetric detection. At the date of publishing,good quality general purpose vibration detectors canbe purchased for a sum of less than £20. Figure 15shows typical applications for general purposevibration detectors. Refer to BS 4737: Part 3 forfurther information.

Application notes for vibration detectors

Decide upon the principle of detection mostsuited to the application, either inertia orseismic. Often, either type may be successfullyused in general applications. As a rule ofthumb, inertia is most appropriately attached toitems liable to be rattled or shaken by anintruder's exploratory action. Drilling, levering,cutting and hammering may most appropriatelybe detected by a piezo electric sensor.

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LI

LI

LI

LI

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Generally, inertia devices are affected by gravity Fig. 15and accordingly their possible mountingpositions are more restricted than thoseapplicable to the piezo electric device whichmay be universally mounted.

Whether inertia or piezo electric based, thedevice must be selected for its analytical circuitprocessing which should be tailored to thelikely forms of attack with immunity to theprevailing environmental vibrations.

It is necessary to decide if the detector shouldincorporate a "double knock" feature. Thisprevents false alarms from single shocks such asthat commonly created by a bird colliding witha window. Even in the double knock mode,single shocks of very high intensity or longduration will still activate an alarm.

The area of coverage may typically extend to aradius of 2.5m under favourable conditions.Hard dense materials transmit vibrations betterthan soft materials. Also joints betweenmaterials may greatly reduce the area ofprotection.

A commissioning tool, rather like a spring-loaded centre punch, greatly assists the accuratedetermination of sensitivity adjustment.However this tool should be specificallyintended for use in conjunction with thedetector being commissioned.

The device should be normally closed, withcontacts that open to the alarm condition, thus,the vibration detector would fail to the alarmmode.

In multiple installations, detectors are availablewith a "first to alarm" LED indication.

Vibration detectors must be firmly fixed to thesurface under protection. Metallic fixingmethods transmit vibrations better than plasticor fibre fixings. Vibration detectors can achievethe greatest reliability and areas of coveragewhen fixed to solid structural components.

Vibration detectors usually have the advantageof low current consumption generally, about10 mA.

The detector should incorporate a tamperprotective mechanism, to activate an alarm ifthe cover is removed or the detector isphysically damaged.

It is necessary to locate sensors away fromcondensation and direct sunlight.

The detector should operate satisfactorily in thefollowing environmental range.

Temperature: 0°C to 40°C

Relative humidity: 10% to 90%

/

Artet.

Vibration sensor and processing circuitry, shown withcover removed. Typical dimensions80mm x 24mm x 20mm.

Typical application to detect attempts to force an entry.

Typical application showing vibration detector andtamper protected door connection loop.

In vault and strong room applications up to 8sensors may normally be connected to one highquality complex analyser, selected for thespecific range of possible attacks. The analysergenerally provides a separate channel for eachsensor with an LED indicator to identify the"first to alarm" sensor and also indicate thecondition of each sensor during testingprocedures. Predominantly seismic devices areused, but where rattling or shaking motion isguarded against, inertia sensors may bepreferable with appropriate matching analysers.

210. For high security, strong room and vaultapplications, the advice of an experienced specialistis most valuable. Reputable manufacturers willprovide the necessary technical support at thedesign stage.

PROTECTION OF SAFES ANDCABINETS

211. Developed from strong room seismic devices,the modern detector specifically for use with safesand cabinets offers high levels of security.

212. The small detectors are mounted on the dooror walls of safes. All fixings must be secure and itis recommended that the base plate is eitherscrewed or, preferably, welded to the safe. Tamper-proof junction boxes ease the interconnection of twodetectors where tests indicate that both the doorand walls require separate detectors. Also, thejunction box facilitates the connection of a flexibledoor wiring loop. Some detectors can be fitted witha swivel plate which can be positioned to cover akeyhole during the alarm set period. Either seismicdisturbance or movement of the swivel plate willactivate an alarm. This will protect against theinsertion of skeleton keys or explosives. Generally,these devices combine the sensor and analyser in onesmall unit and may be connected direct to thealarm system control panel.

213. Commissioning sensitivity adjustments mustbe carried out using a proprietary test transmitterspecifically designed to match the sensor under test.The most advantageous positions for fixing thesensors for maximum range may be determinedprior to installation by the use of a rangeverification device that is used in conjunction withthe test transmitter.

214. Metal is a good carrier of vibrations anddetectors fixed to metal surfaces may have aneffective range of up to 6m. The extent of thisrange however will be seriously reduced on other,less dense materials.

6 8

215. The above is also applicable to all singularitems such as filing cabinets and data storagesystems. In this specialist field of securityprotection the advice of an experienced specialist isof value in determining the most effective form ofprotection. The requirements of manufacturersinstallation manuals and performance specificationsmust be carefully considered prior to the selectionof detectors. For maximum protection, the safeshould lie within a volumetric detector's field ofcoverage, which should also be extended along thepossible routes of access.

216. Refer to BS 4737: Part 3: Section 3.10.

217. The system should be tested continuously forseven days without producing a false alarm prior toits connection to remote signalling apparatus.

SOUND DETECTORS

218. A forced entry, and subsequent intrusionwithin a building creates noise, the magnitude ofwhich may be hardly discernible to the human ear.Different detectors have been developed for use ingeneral types of building and others specifically forstrong room applications. The type used in generalbuilding areas predominantly function in theaudible frequency range. They have a very highnatural susceptibility to false alarms and may beactivated by many extraneous factors such asthunder and passing emergency service vehicles.Accordingly they should not be directly connectedto any alarm activating controls or signallingapparatus. However, a development of this form ofdevice incorporates a manned control station towhich the detector relays, via a telephone line, thesignal that activates the alarm. The operator thendecides whether or not the sound that originatedthe alarm, and the subsequently monitored sounds,merit the issue of a full alarm. Window and doorcontacts can be incorporated to offer a verified formof alarm signal. This unique form of protection canbe most effective in combatting the relativelyignorant, noisy, vandal or opportunist intruder.

219. A monitoring and maintenance agreement tiedto the installing company is usually necessary.

220. The site installation consists of miniaturised,combined, microphone and amplifier units that arestrategically placed throughout the area underprotection. Each unit is connected to a local controlpanel. In the alarm mode, the sound picked up bythe active microphone is relayed by the local controlto the manned, remote control station.

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Fig. 16 Beam detectors

TransmitterBeams, cross each other toprevent gaps in protection.

Transmitter

Cigar shaped microwave barrier of protection.

221. Although referred to as sound detection, inoperation, this type of system may more aptly bedescribed as sound monitoring.

222. Installation and maintenance should be carriedout to the general requirements of BS 4737: Part 3.At the time of publishing there is no separatetechnical British Standard section devoted solely tothis type of detection.

223. The sound detectors for use in strongroomsand vaults need to be applied with specialistknowledge. Since they are normally connected tosome form of alarm signalling, extensive precautionsmust be observed to prevent false alarms. As aminimum precaution, a sound meter is used toconfirm that the detectors trigger level is at least15dB above the ambient noise level. They are mosteffective in strong rooms and vaults whereenvironmental sounds, such as thunder, may not beable to penetrate.62

BEAM INTERRUPTION DETECTORS

Receiver

224. With this type of detector a narrow beam ofinfrared energy or a cigar-shaped beam ofmicrowave energy is transmitted to an appropriatereceiver. When an intruder obstructs the beamfalling upon the receiver, an alarm signal isactivated. The earliest systems cast an opticallyfiltered beam from a filament lamp. This methodhad serious reliability limitations rendering itunsuitable for widespread use. With the arrival ofsolid state components, infrared and microwavesystems have vastly extended the application ofbeam protection. This method of linear protectionis most suited to external perimeters and alonginternal walls, corridors and roofs. Microwavedevices are generally intended for external use only,and often referred to as fence or barrier protection.Figure 16 shows typical arrangements for bothinfrared and microwave installations.

Transmitter Receiver

Both beams must beinterrupted tosignal alarm.

AdditionalTransmitter/Receivercombinations maybe stacked as necessaryto form a 'wall' ofprotection

Receiver

10/100m

Infrared beam protection. Also suitable for use inside buildings.

TransmitterPerimeter fence or Wall

BUILDINGUNDER PROTECTION

Microwave barrier or infra-red beam of protection.

Typical plan of perimeter protection

7 0

Transmitted signals crossto eliminate gaps inprotection.

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Hrtfrared beam protection

225. An LED provides the source of infraredenergy. The LED output is modulated, pulsed, andtransmitted as a narrow infrared beam. The receiveris tuned to match the frequency of the infraredtransmitter. Also, the signal processing recognisesthe frequency of modulation imposed upon thefundamental frequency of transmission.Accordingly, fluorescent and other stray modulatinglight sources are eliminated as false alarm hazards.Optionally, security levels can be improved whereindividual matched transmitter and receiver pairsare tuned to an exclusive, confidential frequency ofmodulation. This prevents the intruder deceivingthe receiver by the introduction of a decoy source ofinfrared radiation.

226. Before the introduction of the high powerLED transmitter fog and rain rendered the deviceunsuitable for external applications. However, inexternal applications, modulated, high-powertransmitters are operated at only one-tenth of theirattainable range and therefore have great toleranceto poor visibility weather. Some receivers have theadditional feature of issuing an early warning alertwhen there is a significant reduction in the receivedsignal due to adverse weather. Protection should beprovided against condensation which is most oftenprovided in the form of thermostatically controlledintegral low power heaters.

227. To form a wall of protection, fencetransmitters and their corresponding receivers maybe stacked above each other ensuring that the spacebetween the beams is less than human size.Immunity to false alarms from airborne debris andbirds can be achieved by connecting the normallyclosed alarm contacts of adjacent receivers inparallel. Naturally, this increases the size of targetthat may pass undetected. Some manufacturersproduce integral twin-beam transmitter units foruse in conjunction with matching twin receivers.Both beams must be simultaneously broken for analarm condition. Beam projection is difficult toconceal and is readily observed by the intruder whomay then seek an alternative route of entry.Detectors are available with obscure covers that donot reveal the direction into which the beam is cast.Circuit wiring should be protected against vandalattack.

228. An extensive range of models exist for bothinternal and external applications. In respect of this,specifiers should research the market to ascertain thetransmitter and receiver combination that is mostsuitably tailored to the particular application.

229. It is essential that beam systems are mountedto stable fixtures and protected from physical

64

movement. Mounting position must ensure thatsunlight cannot directly cast upon the receiver, atany time of the year.

230. Refer to BS 4737: Part 3: Section 3.12.

Microwave beam detectors

231. The antenna of the microwave transmitterdirects a beam of electro-magnetic energy to thereceiver antenna. The design of the antennadetermines the shape of the beam and in mostapplications a cigar-shaped propagation is used.Typically, the pattern of coverage may extend fromground level to a maximum height of approximately3m. The range options are generally 30 to 200mdistance between transmitter and receiver.

232. Microwaves are inherently radio waves andtheir behaviour may be comprehended as thatsurmised by a beam of light, capable of passingthrough non-dense objects and reflecting off metalobjects. Microwave beam detectors sense an alarmcondition when the received signal is disturbed by aphysical object moving within the beam. Someantennae are deliberately designed to possess greatersensitivity to horizontal movement than verticalmotion thereby reducing the risk of false alarmsfrom falling leaves and airborne debris. Present-daysystems are predominantly designed for external useand are constructed to withstand all environmentalconditions and may sometimes be fitted with lowpower thermostatically controlled heaters to preventthe formation of condensation. A sensitivityadjustment enables the optimum level of security tobe attained.

233. The quality of signal processing is in aconstant state of advancement. Digital processingtechniques can be used to evaluate the size andspeed of the intruder, thereby enhancing immunityto false alarms.

234. BS 4737 refers to intruder alarm systems inbuildings, and accordingly, external beamprotection is not within the scope of this BritishStandard. In respect of this, the specifier mustdetermine the technical standard of the proposedapparatus and also ensure good standards ofinstallation practice.

235. External beam detection has evolved fromapplications in high security establishments such aspower stations and oil refineries. In these traditionalapplications the alarm signal is directed to theon-site security desk. Accordingly any false alarmsare contained locally within the establishment.However, with increased criminal activity there is a

k.

trend towards installing external perimeterprotection in more general applications. This hasinstigated the requirement for external protection tobe connected to remote signalling apparatus. Priorto the connection of remote signal equipment theapproval of the local police should be sought. Thepolice may seek an assurance that every reasonableeffort has been made to eliminate the risk of falsealarms. It is advantageous to demonstrate that theselected equipment possesses good quality signalprocessing to provide high levels of false alarmimmunity. Similarly, the site installation should beto a high professional standard. Before an externaldetection system is connected to remote signalling,it should be tested for a minimum period of sevenconsecutive days without producing a false alarm.

SOME TYPES OF SPECIALIST ANDLESS USED FORMS OF INTRUDERDETECTION

236. The following forms of detection are rarelyused in schools. However, designers should beaware of these devices and indeed may want to useone or more of them to overcome a particularsecurity problem, or find thernselves responsible forthe maintenance of existing items.

Capacitive volumetric detection

237. Electrical insulators, including air, possess thephysical quality to store an electric charge. Fornumerical convenience, the amount of electriccharge storage capacity is generally measured inunits of micro farads.

238. In a closed space with a relatively constantlevel of humidity and where there is no electricalequipment operating, a reasonably constant level ofcapacitance prevails in the volume of air in theenclosed space. However, a person entering andmoving within this volume of air disturbs thebalanced conditions and the capacitance of thevolume of the space will rapidly change. Capacitivevolumetric detectors are designed to activate analarm when a person of approximately 60kg movesat walking speed through a distance of 2m.

239. With the advance of other forms in movementdetection these devices are very seldom used todayand may be adversely affected by humidity andextraneous static electricity.

240. Refer to BS 4737: Part 3: Section 3.8.

241. This form of protection must be operated for aminimum period of 7 days, without producing a

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false alarm, before its connection to remotesignalling apparatus.

Capacitive proximity detectors

242. These devices are most commonly used toprotect single items or a small group of itemswhich can be connected together by a single wire.

243. A single wire connects the detector to theprotected object. By virtue of this connection thecapacitance detector and the protected objectachieve a combined balanced, stable level ofelectrical capacitance. When a person touches orbecomes very close to, the protected object a fastrate of electrical discharge occurs resulting in a fastrate of change in the overall level of capacitance.Electronic processing analyses the rate of change andactivates an alarm when the rate of change is greaterthan that which would normally be caused byenvironmental factors. Although changes inhumidity and background static electricity alterapparent levels of capacitance, the change isnormally at a low rate and thereby rejected by theprocessing circuitry.

244. Capacitive proximity detectors are basicallyintended for connection to metallic objects.However, metallic foil fixed to materials such aswood and plastics, permits successful operation.Typically, the back of a valuable work of art maybe screened with a metallic foil that is subsequentlyconnected to a capacitive proximity detector.

245. Refer to BS 4737: Part 3: Section 3. 13.

Rigid printed-circuit wiring

246. In this form of protection hard wiring ispermanently bonded to rigid panels. A two polecircuit configuration is connected to the alarmsystem to activate an alarm upon any of thefollowing occurrences:

E the wiring is cut

adjacent wires touch

E alternative wires touch

the wiring is moved more than 50mm.

247. The rigid panels are fitted in position with thehard wiring to the inside of the protected area. It istherefore extremely difficult to tamper with theelectrical connections or force an entry withoutdamaging the wiring and thereby activating analarm.

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248. In the wake of advances in electronic methodsof protection, this traditional form of protection hasvirtually fallen into disuse. When correctly installedit has a high immunity to false alarms, but is notsuited to damp environments.

249. Refer to BS 4737: Part 3: Section 3.11.

Underground detectors

250. These are activated when a person walks overthe detectors. Although various methods haveevolved over past years, the hydraulic pressuresystem is most commonly employed and isextensively used in high security installations suchas refineries and power.stations.

251. Two fluid tubes run beneath the groundapproximately one metre apart. Bleed connectionbetween the two tubes ensures that the systemstabilises with the two tubes at equal pressure.When an intruder or vehicle moves across the twotubes a very slight pressure differential is createdbetween the tubes. A highly sensitive pressuresensor will then activate an alarm signal. Thissystem of protection has relatively good immunityto false alarms from small animals and cannot easilybe defeated by such methods as placing a plankacross the ground above the two tubes. Unlikebeam detection this underground method can besatisfactorily used in an area of uneven terrain.

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Microphonic cable

252. Such a cable is primarily intended to berouted along and interwoven with chain linkfencing, the cable acts as a transducer, convertingmechanical vibrations into equivalent electricalsignals. In most applications, the cable endsterminate at a control panel situated in an on-sitemanned security desk. When the fence is cut orclimbed, an alarm threshold is exceeded and analert signal is issued. The audible sound of theattack is reproduced at the security desk, indicatingthe type of attack. This form of protection is mostoften referred to by one of a number of proprietarybrand names.

New detection techniques

253. Developments in electronics andmicroprocessor technology will continue to bringforth new methods of intruder detection. Existingforms of sensor will benefit from "intelligence" thatwill enable the detector to monitor its owntechnical functioning and also its ambientenvironmental conditions.

254. The application of laser beams and opticalfibre techniques may advance into everyday securityapplications. Already, optic fibres are employed inhazardous environments where gases, flammableliquids and other corrosive substances renderconventional cables inappropriate.

APPENDIX 2 Atuciliary equipment

255. Apart from the main operating components ofan intruder alarm system there are other essentialparts. These serve to interconnect the entire systemand provide for the particular requirement of anyscheme.

256. This appendix describes the most commonlyused components that may typically be found in anyintruder alarm system.

Deliberately operated devices

257. Commonly referred to as panic buttons orpersonal attack switches they are designedspecifically for either hand or foot operation. Thedevices must be simple to operate but incorporatedesign features to minimise the risk of accidentaloperation. Hand operated switches have one or twosimultaneously operated buttons, shrouded forprotection against unintentional operation. Thedevices should be fitted with terminals for bothalarm and tamper connections.

258. Deliberately operated devices are most likelyto be used during periods of building occupancyand should therefore be connected to a control panelpossessing a 24-hour armed circuit. To reduce therisk of personal attack upon the user, the deviceshould be fixed in a discreet location requiring avirtual absence of noticeable movement in order forthe operator to activate the device.

259. Careful consideration must be given to thesignalling mode. In some instances a loud, localaudible alarm may pose a greater risk to the personunder attack. BS 4737: Part 2 details specificrequirements for basic systems and more complexsystems incorporating remote signalling. Wire-freesystems as detailed further herein, provide forcompletely portable deliberately operated devices.

Security Rock switch

260. This normally consists of a high-quality 5lever mortice lock into which a switch with changeover contacts is fitted. Usually the contacts used aremade (unlocked) and open (locked). The switch maybe used in the first/final entry door to signal thecommencement of an authorised keyholder's entryor completion of an authorised keyholder's exit.When used in systems incorporating remote

signalling, there is a reduced likelihood of falsealarms resulting from inadequate entry and exitprocedures. The lock switch initiates a pre-settimed entry period enabling the keyholder to enterthe premises and walk through a defined entryroute to the control panel and hence disarm itwithout initiating an alarm. Similarly, the lockswitch may be used to signal the completion of theexit procedure. The entry and exit routes betweenthe outside and the control panel are normally thesame, but it is permissible for them to followdifferent routes. In basic systems a magnetic contactincorporated in the first/final entry door signalsinitiation of entry or completion of exit. To placesole reliance on door contacts means that anintruder who attacks this door has the benefit of thetimed entry period after activating the door contactsbefore an alarm is raised. Where a lock switch isused to signal completion of exit, a magnetic doorcontact can be used to initiate an instant alarm ifthe door is forced open. This combined treatment ofthe door can only improve the level of securitywhere the keys to this point of entry are securelykept and not duplicated. Where reliance is placedsolely on a magnetic contact, fitted to the door,false alarms may arise from the exit procedure, ifthe door reopens. The door must be thereforelocked in the closed position prior to expiry of theexit time period.

261. In another application, the lock switch is usedto temporarily discomiect a section of the protectedarea where partial occupancy of a building isfrequently required. In some schools, holiday periodaccess may be required only to defined areas such asbasements, plant rooms and cleaners' stores.Accordingly, the specific areas may be convenientlyshunted out by the lock switch whilst theremainder of the school remains protected. Thereare some schools where high risk portableequipment such as computers and audio equipmentare stolen during periods of legitimate occupancy.Where this problem exists it is desirable to protectthe individual high risk areas on a 24-hour basis.The protection is only isolated at the actual times ofoccupancy of each individual computer room orother similar high risk areas. To provide 24 hourprotection under local control, the 24-hour alarmloop is used to serve the protected space and iscontrolled by a shunt lock that is fitted to the roomentrance door. The shunt lock should be connectedto a proprietary zone omit unit, or similar device,to prevent an isolated area being reconnected whilstit is in alarm mode. The multi-user nature of school

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Tamper protectedconnection boxes.

Flexible connectionloop. (May bearmoured cable)

Fig. 17 Door connection loop typical application

teaching areas increases the number of persons incharge of access thereby increasing the likelihood ofuser induced false alarms. As a further move againstfalse alarms, a door contact could be interconnectedwith the room detector to prevent an alarmactivation if the shunt lock is locked closed whilstthe door is open.

262. Refer to BS 4737: Section 4.1.

Door connecton loops

263. To facilitate flexible connection to devicesfitted to openings such as doors and windows, pre-assembled wiring loops are available. They are madefrom tinsel cable to provide a highly flexible anddurable interconnection. Where extendable loops arerequired, coiled cable, similar to that connected totelephone hand sets, are used. Where vandalismmight occur flexible metal sheathed door loops isrecommended. At least one LEA has found itnecessary to standardise on a highly vandal resistant

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armoured door loop of a type that is made to recessinto the hinge side of the door frame. These areparticularly recommended for connections to thefinal exit door where a security lock switch is fitted.

264. The interconnection between the door loopsand the system hard wiring should be made withtamper protected connection boxes, as shown inFigure 17.

265. Refer to BS 4737: Part 1: paragraph 3.3.5.

ItIIIIction boxes

266. For the interconnection of security wiring,appropriate security junction boxes must be used.Any other form of connection box invites theintruder to easily disable the alarm system. Junctionboxes should contain contact materials that will notdegenerate in the atmosphere and may typicallyconsist of nickel-plated phosphor-bronze. The covershould be impact resistant and designed to activatea tamper signal upon its removal.

PVC cables for interconnecting wiring

267. Cables must be of an adequate cross-sectionalarea to ensure that the potential difference acrossthe furthest detectors is at least equal to theminimum working voltage stated by the devicemanufacturer. Ideally, reasonable tolerance shouldbe allowed for further extensions to the system.

268. The most commonly used cable has strandedcores comprising 7, 0.2mm diameter tinned copperconductors. It is generally available in multiples oftwo cores from 4 to 12 core arrangements. To alesser extent solid core, telephone type cable is usedbut its relatively small cross-sectional area imposes agreater system voltage drop, also its singleconductor cores are less flexible and may thereforebe more susceptible to mechanical damage. Screenedor shielded cable can be used to improve physicalprotection to the cores and also reduce thesusceptibility to induced electrical or radiofrequency interference.

269. Where environmental conditions prohibit theuse of PVC cables, alternative wiring systemsshould be considered but importance should beattached to cable security and tamper sensitivejointing boxes. MICC cables and other wiringsystems, installed in accordance with the latestedition of the IEE Regulations for ElectricalInstallations, may offer suitable solutions.

270. Refer to BS 4737: Part 3

End of lines devices

271. This may refer to a resistor or any electricalcomponent that establishes a potential difference atthe point where a circuit apparently terminates.

76

272. Resistors fated at the furthest point, orapparent end of individual circuits, can be used toprove a circuit of continuity possessing a definedvalue of electrical resistance. Thus, if cables are cutor short-circuited a tamper or alarm condition canbe activated by a compatible control system.

Batteries

273. Batteries incorporated with, or mountedadjacent to the control panel are used to power thealarm system during periods when the normalelectricity supply is unavailable. In the event of analarm arising during a power breakdown, batteriesmay be required to power local and remote alarmsignalling. The important role of batteries must notbe overlooked since the vulnerability to break-insincreases during periods of power failure:

274. The power requirements of the alarm systemcan be calculated from the technical data of thedetection and alarm devices. Accordingly it ispossible to determine the ampere-hour rating of thebattery necessary to power the system in botharmed and alarm mode. BS 4737: Part 1: Para7.2.1 details an 8hr battery capacity requirementfor powering the alarm system in the normal mode.Also the associated charging equipment mustrestore the charge to the battery within 24hrs.

275. The above text specifically applies to systemsincorporating rechargeable batteries. However, othersystems utilise a primary battery and here thebattery must be capable of sustaining an alarmcondition for a minimum period of 4hrs within theservice life of the battery. The battery should bear amark stating the date at which it was installed andregular replacements must be made prior to theexpiry of the normal service life of the battery, asstated in the battery manufacturer's instructions.

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APPENDIX 3 Wire-free intruder alarm systems andportable alarms

276. In 1986, BS 6799 wire-free intruder alarmsystems was issued. Manufacturers have nowproduced systems in compliance with BS 6799 andthey have already been used in some schools where afully wired system is inappropriate.

277. LEAs have experienced problems with self-contained portable alarm systems but they may helpto defend a particular target until a proper alarmsystem is installed.

278. This appendix describes both wire-freeintruder alarm systems and also the stand aloneportable alarm.

Wire-free intruder alarm systems

279. This form of intruder alarm system utilisessome of the same detection technologies as hardwired systems. Using radio as its communicationmedium the interconnecting wiring betweendetectors, local alarms and controls is dispensedwith. Small battery powered radio transmitters areeither incorporated in the detectors, or fittedadjacent to the detectors. In the event of a detectorsensing an alarm condition a radio signal istransmitted to the control receiver whichsubsequently activates the local audible alarms andany relevant remote signalling equipment.

280. At the time of publishing, many local policeforces are reluctant to accept remote signalling callsto attend to premises where wire-free alarm systems

Fig. 18 Typical school application for awire-free intruder alarm system.

Combined PIR detector and radiotransmitter senses intruder and \signals alarm. \ \

)6

are installed. This is largely due to the high levelsof false alarms attributable to the poor quality ofearly imported wire-free alarm systems. Beforeinstalling a wire-free alarm system connected toremote signalling equipment, early liaison with thelocal police crime preveption officer is essential. Asa minimum the police are likely to insist that anysystem fully complies with BS 6799. BS 6799issued in 1986 defines five categories of wire-freealarm systems. Also the Department of Trade andIndustry Radio Regulatory Body has issuedtransmitter specification requirements. Class IV andClass V have the highest security integrity. Class Vsystems intercommunicate with each transmitterand report on its input status and battery conditionat maximum periods not exceeding 1.2 hours. AClass V system will also activate an alarm signal if areceiver has not had an input from a remotetransmitter for a maximum period of 3.6 hours.Class IV systems are required to perform both thesefunctions but within the extended period of amaximum of 8.4 hours. The other three lowerclasses of system do not possess this level of auto-reporting and thereby have a lower level of securityintegrity. Since the issue of BS 6799 manufacturershave tended to direct their development effort intoproducing Class IV and Class V systems for use infairly large commercial premises. The use of a highgain tuned receiver aerial may permit the system tobe extended to a number of building blocks allwithin reasonably close proximity. Maximum

Alarm signal received atschool keepers house.Local alarm raised.

Combined, receiver,transmitter andcontrol panel locatedin school keepers house.

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CJIMIOGINNE00000CM00000000C00

Alarm signal may beextended to monitoringstation by telephone line.

Monitoring station will pass onalarm message to appropriaterespondents. Note: local policeforces may not be agreeable toaccepting calls emanating from wire-free alarm systems.

VDU store, fitted withdoor contact and radiotransmitter.

School application for a wire-free intruder alarm system.

14/

I I 4

transmitter range is attainable when the receiver isfitted with an external high gain tuned aerial.Furthermore, if the detector transmitters arepositioned reasonably high above ground level andpreferably if they are in line of sight communicationwith the receiver aerial, maximum communicationdistances will be achieved. Dense concrete andstructural steelwork may seriously reduce attainabletransmitter ranges.

281. The importance of regular, frequent auto-reporting cannot be overstated. If a radiotransmitter is removed or its battery fails, a securityexposure will exist until the control receiver reportsthat the transmitter has not 'called in' by theperiodic time. Hard-wired systems have theadvantage of tamper circuits to address the securityexposure associated with detectors being deliberatelyremoved.

282. In order to achieve a reasonable service lifefrom batteries, transmitter power and auto-reporting rates have to be limited. Similarly activedevices such as ultrasonic detectors require toomuch power to permit a useful battery life.

283. Specially developed passive infrared detectorscontain a transmitter and aerial and also possess theability to conserve battery energy during thedeactivated period by holding the sensor in aquiescent state for a few minutes after each sensoractivation. This is particularly relevant in areas ofhigh occupancy levels where the device could bevery frequently activated. For exceptional reasons,in some situations, it may be possible to derive alocal mains power supply to drive a power packcontaining secondary batteries, which themselvescan be used to provide a supply to any commonform of detector, whilst the transmitter retains itspower source from its integral battery.

284. Class IV and Class V wire-free systems offer avery good alternative when a hardwired system isimpractical, although it must be remembered thathardwired systems offer the highest levels ofsecurity integrity. Wire-free systems have aminimum impact upon the decorations and fabric ofthe building and may often be installed where thepresence of asbestos could prevent a hard wiredinstallation. Compared with hard wired systemsthey require much less labour for the installationprocess. However, the transmitters and receiversignificantly add to material costs. The need forbattery replacement, every six months adds to themaintenance commitment. It is an advantage ofwire-free systems that personal attack buttons aretruly portable. Diligent commissioning is essentialsince many unforeseeable factors may adverselyaffect the ability of the transmitter to communicatewith the receiver at the appropriate time.

7 s

Commissioning checks should be carried out inconditions relevant to that applying when thesystem is armed throughout all periods of the year.Actual application experience on the part of theperson specifying the system and the engineerinstalling it is most vital. Interference from naturalenvironmental sources and from electrical planttogether with the effects of multi-path receptioncreate considerable problems which the experiencedengineer may find reasonably easy to identify andresolve.

285. BS 6799 provides recommendations for theconstruction and installation of wire-free alarmsystems. Explanatory details are provided for each ofthe 5 categories of wire-free alarm systemclassification. Figure 18 shows how a wire-freealarm system may be applied to a school site.

Portable alarms

286. Stand alone portable alarm units for spaceprotection generally consist of a movement detector,integral controls, siren, and strobe light. They mayscare off the casual opportunist intruder but are easyto physically damage and thus deactivate thereforeposing very little deterrent to the experiencedcriminal. In fact, portable alarms have been stolenalong with other items.

287. Some LEAs report that a number of factorsmake these portable units vulnerable to false alarms,particularly that they are often "aimed- into avolume of space by persons with no technicalknowledge in respect of detector sensitivity toenvironmental factors. The high false alarm riskrenders the units unsuitable for remote signalling tothe police.

288. Portable alarms can usefully be employed inschools that suddenly become targets for intrudersor as a temporary measure in vulnerable buildingspending the installation of a fixed intruder alarmsystem to BS 4737.

289. A new generation of low cost alarms forbonded attachment to audio-visual equipment andcomputers can be effectively used where it isnecessary to remove equipment from safe protectedareas. An ear-piercing sound is emitted when theitem is moved and latches into a continuous alarmmode until the system is reset by a key. Thedifficulties of stealing a video recorder with a loudsiren attached to it are self evident.

290. The above text describes typical portable alarmsystems. However, there is a considerable numberof different proprietary systems available.

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APPENDIX 4 Intruder alarm system control panels

291. Intruder alarm system control panels serve asan interface between the different components of thesystem and the user of the alarm system. They mustbe selected to be compatible with the extent andtechnology level of the system. Similarly they mustact as a suitable interface to any signalling ormonitoring equipment. For schools it is importantthat the controls are 'user-friendly' to the personwho may be new to the alarm system. Figure 19shows a typical example of modern control panel.

292. This appendix describes the types of availablecontrol panels.

293. It was not many years ago that intruderalarm control panels consisted of an assembly ofelectro-mechanical relays. This relatively simpleconcept has now fully entered the micro-computerera with some "intelligent" control panelsincorporating their own micro-computer. Theproblem facing today's specifier is the need to selecta control panel that is compatible to the pattern of

use of the building into which it is to be installed,yet at the same time, be user friendly and not betoo limited or Complex for the job in hand. Cost isvery much proportional to the degree of technologyemployed. Essentially, controls must be fullycompatible with the types of detection devices,together with their associated remote signallingequipment.

294. The system of wiring and any associatedoutstations, will generally be installed to suit thetype of system dictated by a proprietary controlpanel. There is no need to describe here all theproprietary types of control systems and associatedinstallation wiring methods available at the date ofpublication. However, for general guidance a briefdescription is included detailing traditional wiringfor small systems and also a typical large multiplexsystem. In any type of system, consideration shouldbe given to the almost certain need to expand orreprogramme the system to suit changes in thebuilding's pattern of use.

Fig. 19 Typical arrangement of a modern micro-processor based intruder alarmcontrol panel.

User enters personal IDcode to gain access tocontrol options. Pushbuttons used in responseto displayed prompts toset or revise controlparameters.

72

'WO alppcpupt Mat 7-_;Alr13

YES

ENTERCOMMAND

CANCEL

ZONEOMITTED

Light warns when part ofsystem is disarmed.

Typical dimensions350mm high x 250mm widex 100mm deep.

Printer socket for usewith portable printerto record history of events.

295. Under the headings of "small and traditionalcontrols" and "microprocessor based controlsystems- there are lists of optional operationalfeatures. The specifying engineer can draw from thelist to assess operational requirements for anyproject at the embryo stage. The operationalrequirements thus obtained may be comparedagainst manufacturers' specifications. Figures 20 and21 show the typical wiring systems for bothtraditional and microprocessor based systems.

Small arid traditional control systems

296. Microprocessor technology is used in alimited form and with most low cost control panelsgenerally a maximum of 6 zones is provided.Outstations for expanding each zone of the sytemare unlikely to be a feature of this limitedtechnology. However, the system possesses all thenecessary basic controls and programming optionsnecessary for a satisfactory installation. Theinstallation system of wiring is predominantly of thetraditional radial method, separate for each zone.

297. Inside the control panel, input terminals areprovided for each zone. Additionally, a nominal 12volt DC supply is provided by a pair of terminalsand two further terminals serve as connections forthe tamper loop. Finally, connections are providedfor a 24-hour personal attack loop.

298. The traditional method of wiring serves eachprotected zone by a separate radial circuit.Typically, a 3 pair PVC cable will carry the zonealarm loop, tamper loop, and DC low voltagepower supply connecting to each successivedetector, on each individual zone. A similar cableserves the local audible alarm.

299. Output terminals are provided for the localaudible alarm. One pair of terminals energises thesounder in its alarm mode and another pair providespower to the local audible alarm's integral batterycharger. This charging supply may also combine thehold-off function which prevents the sounder beingenergised by its integral battery whilst the controlpanel and its charging supply is healthy. Thus, ifthe cable serving the local audible alarm is cut, theaudible alarm will automatically be powered by itsintegral batteries to sound an immediate alarm.Additionally, a separate latching alarm output maybe used to power a strobe light until the controlsare reset.

300. There is considerable variance in the featuresoffered by intruder alarm panels of differentmanufacturers and price range. However, thefollowing list is indicative of minimum basicrequirements:

80

Terminals provided for entry/exit route withadjustable time delay.

Part set option leaving one zone only de-activated, for periods of partial occupancy.

Terminals for connection to digitalcommunicator.

Test facility enabling deliberate activation ofdetectors without raising an alarm condition.

Visual indications of alarmed zone, tamperactivation and entry/exit route time overrun.

Setting arrangements are traditonally by multi-position key switch with a keypad provided onmore sophisticated controls.

Adjustable timer, capable of 20 minutessetting, for use with local audible alarm supply.

12/15 volt regulated DC power supply able todiscriminate between normal load and chargeconditions.

301. For a primary school or other building ofsimilar size, this simple form of control system canbe effective and economical. Too much should notbe expected since low cost controls often lack thepower to drive more than a few movement detectorson any given zone. Similarly, control andprogramming options may be limited. It isadvisable to allow some spare capacity to enablefuture extensions to the detector circuits.Preferably, at least one spare zone should beallowed.

302. It is essential to compare differentmanufacturers' specifications to select a controlpanel of the optimum technological sophisticationfor the needs of the premises to be protected.Setting and switching off procedures should not becomplicated, particularly where temporary staff mayfind themselves responsible for managing the alarmsystem controls.

Microprocessor based control systems

303. Microprocessor based control panels extendthe capabilities of intruder alarm systems evenfurther. Future technological developments willcontinue to bring forth new generations of intruderalarm control panels with greater data-processingpower and more flexible, user friendly programmingprocedures. At the date of this publication,multiplex control panels, with keypad programmingand operation (setting controls) have provedthemselves reliable in service. Programming iscarried out in conjunction with a real languagewritten display that asks the user to enter theanswers to simple questions. The "intelligent"control panel is a further development with the

73

Fig. 20 Example of the traditional radial method of wiring with basic type controlpanels.

Zone

4,--Typical 6-core cable radially routedto hard wire each defined physicalzone of protection

Zone 4

Traditionalbasic typecontrolpanel withcommunicator

Fig. 21 Example of a typical wiring system used with microprocessor based controls.

6-core cablebetween eachdetector andits local \ I

outstation.

Zone 3

Zone 2

74

Typical 2-core cable linksoutstation expansion units.

Zone 4 /

"-

TJ-

"91

Typical outstation expansion unit serving upcto 10 detectors.

By means of telemetry between the controlpanel and outstation expansion units asingle 2-core cable may serve a group ofindividually programmable sub-zones.

Spare additional main zones which may beexpanded by use of outstations.

Zone 1

co

CO

C

Typicalmultiplexcontrolpanelandcommunicator

ability to monitor and report the condition of thecontrol system and any compatible, self monitoring"intelligent" detectors that are connected to thesystem. Advantageously, a technically deterioratingdetector or a near false alarm condition will bereported enabling remedial action to restore securityintegrity or eliminate a pending false alarm.Condition reporting is through a central station towhich the control panel must be dedicated.Therefore the system owner is often tied to themonitoring company's service and its related fees.

304. With keypad operation system access is bythe entering of a personal ID code. Unfortunatelysome LEAs have reported that ID codes have beenpassed on to unknown numbers of unauthorisedpersons. Therefore an important aspect ofmanagement is to ensure that personal ID numbersare regularly changed and that users are made fullyaware of the need for confidentiality. Manufacturerscan often incorporate a master key switch ifsufficient customer demand exists, but a reasonableuser attitude would dispel the need for thisrequirement.

305. Such is the extent of technical complexity ofmultiplex, or computer-based, intruder alarmcontrol panels that the purchaser of a system needsaccess to independent expertise in order to correctlyevaluate the technical performance and value formoney aspect of systems produced by competingcompanies.

306. A wide range of proprietary systems ofinstallation have evolved but a generally commonfeature is the use of telemetry and outstations, tominimise system wiring, and also form a remotepoint of connection local to the detectors in anyarea or zone. Generally, the basic multiplex systemretains the traditional method of providing separateradial cables to serve each main zone but utilisestelemetry and outstations to serve as convenientpoints of connection for local groups of detectorcircuits. Individual outstations may be programmedfor specific control options, such as 24-houroperation and timed entry/route functions."Intelligent" systems employing a higher degree oftelemetry dispense with the need for hard wiringto each major zone. Instead, normally only onesmall multi-core cable is radially routed throughoutthe building to the outstations. Effectively, zoningis achieved by giving each outstation an addressreference, that can be individually programmed,from the control panel keypad. The basicprogrammable options include 24-hour protection,entry/exit route definition and timing and, withmore advanced systems, scope for programmingvarious disarm patterns to suit required patterns forpartial occupancy.

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307. The following list schedules the basicfunctions typically possessed by a multiplex system.Additionally, the list is extended to include extrafeatures relevant to the condition monitoring andreporting, so-called intelligent controls. Thespecifier is recommended to carefully compare theoperational specification offered by products ofcompeting companies and to also consider therelative long-term cost commitment. With someproprietary systems it may not be possible tocompetitively tender maintenance and monitoringservices.Multiplex and computer-based systems operationalfunctions should:

O Comply with BS 4737: Section 4.1

Be user friendly and simple to operate by newor temporary staff.

Provide keypad operation with option foradditional remote keypads

Carry log-on codes for authorised persons to setor disarm the system with master code forprogramming system control parameters.

O Provide real language display of setting process,programming and alarmed zone identification.

Possess an event memory of settings, alarmsetc. with memory print out by an optionalintegral printer or alternatively terminalsprovided to accept a portable printer.

Allow any activation and de-activation times tobe selected.

Provide control capability to address outstationsor individual circuits derived therefrom forprogramming options. For example entry/exittimer, 24-hour protection and compatibilitywith local shunt locks. It is recommended thatmanufacturers' specifications are closelyscrutinised to determine the extent of thisfacility which is so vital to buildings withchanging patterns of use. Note: Manufacturershave their own proprietary terminology todescribe the term oustation as used herein.

Provide a facility for integral or add-on digitalcommunicator.

Provide for auto-reset option after alarmcondition. (Use of this option usually requireslocal police agreement.)

Provide self-monitoring of microprocessorsystem and auto-restart optionally available.

(11 General features should include: personal attackcircuit; timer for delay and duration of localaudible alarms; strobe light latching circuits;part set facility; visual indication of live mainssupply; audio and visual indication of alarm

75

condition or tamper activation; testing facilities.

LI The case control panel and its mountingbackplate should be protected with tampersensitive switches.

Provide high capability telemetry betweencontrol panel and outstations to minimiserequirement for hard wiring.

Additional features applicable to computer-based(intelligent) controls

Whilst an "intelligent" system functions inmuch the same way as other microprocessorbased alarm systems, their computing ability isused to provide various levels of conditionreporting upon individual detectors togetherwith the systems functioning as a whole.Similarly, flexible programming can assign atailored control panel response to fault or alarmsignal from any individual detector.

In conjunction with telephone linecommunication to a suitably programmedcomputer located in a central control station, aVDU will inform the station operator of theexact course of action relevant to any fault oralarm signal from any detector. Differentresponses can be programmed for any assigneddetector. This level of central station supportmay only be available from the companymarketing or installing the particular controlpanel. Accordingly, recurring charges cannotalways be competitively tendered.

Constant system monitoring for faultconditions, with an option for remote controlstations to isolate any failed detectors but retain

76

healthy parts of the system in-operation.

Automatic monitoring of level of backgrounddisturbance occurring at the detectors. Warningissued to control station when disturbanceapproaches the detector's alarm threshold level.This offers the opportunity for remedial work toeliminate a pending false alarm condition.

Completely flexible programming of zonegroupings enabling any selected detectors to begrouped, or regrouped into chosen zones.

Double knock option. Initial detector activatedand control station alerted. Full alarm is notraised until a second detector is activated. Thisis a compromise in the level of security but itmay greatly reduce the occurrence of falsealarms. This should not be needed in a welldesigned installation.

il Control system should incorporate a powerfulevent memory. To additionally record operatoridentification and fault information. These maybe time-logged. Option may be available for aprint-out of these conditions.

Facilities may be provided for theinterconnection of other building services suchas freezer/high temperature alarms, and otherplant controls with intelligent informationalerted to central control station.

"Intelligent" control systems are usuallydeveloped to work in conjunction with"intelligent" detectors. The specifier shouldsatisfy himself that suitable detectors areavailable for the particular application for whichthe security system is being planned.

83

APPENDIX 5 Alarm signalling local audiblealarms and remote signalling

308. When the control panel is in the alarm statusan alarm output signal is provided. This signal canbe used to activate a local audible alarm that maytypically consist of a bell or siren. Additionally,remote signalling equipment can be activated to usea telephone line to remotely signal the alarm.Usually advice of the alarm is passed on to thepolice.

309. This appendix describes the various methodsfor signalling an alarm activation starting with theexternal audible alarm.

External audible alarms

310. The audible alarm is distinctly recognised asa box, fixed to an external elevation of a buildingunder protection. In order for this unit to beeffective the following basic criteria should be met:

The housing should be resistant toenvironmental degradation and constructed todefy the attachment of hooks or ropes or theinsertion of expanding foam. Tamper switchesshould operate if the cover is removed or if theback of the unit is prised from the wall towhich it is fixed.

fl The sounder may consist of a conventional bellor a modern two-tone siren but in either casethe sound level measured at a distance of 3m,should not be less than 70dB (A). The "sound"should be distinguishable from other types ofalarm sounder at the same premises.

fl Rechargeable batteries shall be installed withinthe sounder housing. Under normal alarmconditions, the control system will power thesounder. When an attack is made upon theexternal audible alarm or its wiring from thecontrol system, the internal batteries shall beused to power the sounder. A charging circuitshall be capable of restoring the batteries within24 hrs.

3 1 1. In order to comply with the Control ofPollution Act 1974 and the Code of Practice onNoise from Audible Intruder Alarms 1982, it isdesirable that a cut-out timer is provided with thefacility to mute the sound after a maximum periodof 20 minutes operation. Where distinction fromother audible alarms is advantageous, a strobe lightmay be fitted to the housing and may continue topulse after expiry of the 20 minutes until thecontrols are reset.

Fig. 22 Local audible alarm, typical arrangement.

Cover and backplate fittedwith tamper contacts.

Outside wall.

Strobe light and lens.

Terminals.

Bell or siren.

Expanding foam detector(optional).

Rechargeable batteries.

Charging circuit.

84

1

4.s

77

312. The external audible alarm should besecurely fixed at a location in a prominent positionprotected from accidental damage or a deliberateattack. However, attention should be given to easeof access for servicing personnel such that they mayperform their tasks within the terms of the Healthand Safety at Work Act.

313. Dummy, audible alarm housings may befitted to all elevations to confuse the intruder andact as a deterrent. Figure 22 shows a typicalexternal audible alarm.

314. Refer to BS 4737: Part 1.

Internal audible alarms

315. An extremely loud, two-tone, type alarm canbe effective in disorientating the intruder andencouraging a premature retreat. Ideally, the soundlevel measured at 3m distance, should be greaterthan 70dB(A) but less than the threshold of pain of120dB(A). As a first line of defence the alarmshould be fitted with anti-tamper contacts.

316. External audible alarms, with their tamperdevices and integral secondary battery pack, may beeffectively used in internal environments. Wheredisturbance to neighbours isunlikely from aninternal alarm, the external feature of a 20 minutecut-out may be dispensed with.

317. Refer to BS 4737: Part 1.

Remote signalling apparatus

318. When an intruder is detected, most systemswill set off the local audible alarms. The ringingbells would usually alert members of the publicwho would bring the alarm to the attention of thelocal police. -However, as the number of intruderalarm systems has increased false alarms havebecome common-place.

319. In many localities local audible alarms cannotbe relied upon to reach the attention of the police.The enforcement of the Control of Noise Orderrestricts the sounding of an alarm to a maximumperiod of 20 minutes. Buildings within their owngrounds or remote from public awareness areparticularly vulnerable when reliance is solely placedupon the local audible alarm. To overcome theseproblems many systems use special equipment toraise a remote alarm.

320. Communication equipment, often in thecontrol panel, utilises a telephone line to alert an

78

alarm activation. Generally this information isrouted through to the local police via the BritishTelecom lines or to a private central control station.Local police forces have intruder alarms policieswhich entail withdrawal of police response after apredetermined number of false calls, typically fourin twelve months. This conserves police manpowerand at the same time benefits the owners of reliablewell-managed alarm systems since their credibilityaugurs well for an urgent police response. In respectof this, the transmitted information must be clearand concise, and the police should be regularlyupdated with correct keyholder details.

321. There are two common types of remotesignalling apparitus.

Auto diallers

322. Basic units may be programmed to dial anyone telephone number and subsequently play a pre-recorded tape message to the answered telephone.

323. Multi-message units are also available. Thesewill relay the appropriate taped message to any oneof three pre-programmed numbers. Usefully,intruder, fire alert, and engineering plant failurecan be incorporated. With some auto diallers it ispossible to make successive calls such that theschool keeper can be alerted immediately after the999 call.

324. For intruder alarm applications it is mostcommon for the unit to dial "999" and play a tapedmessage to the British Telecom emergency operator.Since the taped message constantly repeats itself itmay be simply connected to the local police controlroom. From here the police will usually issue aradio message to the nearest available patrol car. Itis essential that all such equipment be connectedwith the prior agreement of the local police, sincerequirements can vary from one area to another.

325. Where the telephone line used is that of thenormal occupants it is recommended for the BritishTelecom change-over switch to be fitted adjacent tothe alarm control panel. It is also useful to providea telephone line testing socket at that location.

A to diallers operational requirements

Reliability. These units contain both electricaland mechanical components that must work,first time, and every time an alarm conditionoccurs. They are not self-monitoring andregular testing is essential. The unit should bemanufactured to a very high standard and

8,7)

approved by British Telecom or other relevanttelecommunication authority. Older models areoften claimed to be unreliable.

Contingency alarm. In the event of the intruderalarm control panel signalling an alarmcondition, the occurrence of any of thefollowing shall cause the immediate activationof the local audible alarm: failure of tapemessage, telephone line fault; or line jammeddue to incoming ringing.

In conjunction with a compatible alarm controlpanel, a time delay facility may be available forthe local audible alarm. This facility should beused with care as delay can give intrudersadequate opportunity to steal, cause damage orstart a fire and escape before the alarm sounds.

The unit should incorporate a surge arrestor toprotect against the transient effects oflightning, or other induced voltage on thetelephone line.

fl The unit should be tamper protected.

Digital communicators

326. Digital communicators are made to beplugged-in and hence incorporated insidecompatible control panels or, when in their ownenclosure, be positioned adjacent to the intruderalarm control panel. Effectively, they areinterconnected between the output of the alarmcontrol panel and the input to a telephone line.When an alarm is activated, the digitalcommunicator's output locks onto the telephoneline and waits a few moments for acknowledgementof the dialling tone. Automatically, a pre-programmed telephone number is signalled. Thepublic telephone network makes contact to a centralstation receiver whereupon the receiver returns anacknowledgement signal confirming to thecommunicator a successful connection. Thecommunicator then releases a customer codefollowed by an appropriate alarm code. Thecustomer's premises is identified and the alarm codeis translated at the control station to enable theoperator to take the appropriate course of action.Typically, digital communicators are capable oftransmitting up to eight separate codes which mayinclude such items as alarm status, first and secondknock conditions, system open time, system closedtime and other signals including those relating tothe fire alarm or other services. When the fullmessage has been received the central station issuesa close down signal enabling the digitalcommunicator to release the telephone line inpreparation for a future activation. If thecommunication link fails, the digital communicator

should make at least two more dialling attempts.After which some digital communicators can pursuecommunication on an alternative pre-programmedtelephone number. An output should be providedto instigate an immediate local audible alarm ifcommunications cannot be established during analarm activation. Often in conjunction with acompatible alarm control panel, a time delay maybe available for the external local audible alarmcircuit. The digital communicator should be capableof on site re-programming such that it is simple tochange to an alternative monitoring servicetelephone number.

327. For applications where an exclusive telephoneline is not provided, connections to the digitalcommunicator should be arranged to be capable ofpermitting use of the telephone without activatingan audible fault condition during unarmed periodsof occupancy. A visual indicator on the controlpanel should indicate the apparent loss of telephoneline. It is imperative that the digital communicatoralways functions correctly under an activationsignal. In respect of this regular testing andmaintenance is essential.

328. In conjunction with computer based controlpanels, it should be possible to programme an auto-test between the digital communicator and centralstation receiver to periodically monitor the integrityof the communicator's transmitter and its associatedtelephone line. This is a feature that should be usedwith care to avoid high telephone call charges. It isextremely important that digital communicators arefully compatible with the central station receiver. Inrespect of this the technical specification should beexamined in preference to manufacturers' salesliterature. With the advent of more digital telephoneexchanges there is greater scope to make use of fastformat digital communicators.

329. Unlike the 999 auto dialler, digitalcommunicators must be used in conjunction with acentral station and the subsequent additional costsshould be considered in viability studies.

Remote signalling communication medium

330. Communications should be viewed as an all-embracing concept. Accordingly, the choicesbetween auto-dialling, digital communication ordirect line continuous computerised monitoringshould be taken together with the type of telephoneline to be used. Telephone lines are vulnerable at apoint where they enter a building. Greater securityexists when they are run underground to emergeinside the protected building.

79

Basic exchange lines

331. This low cost method utilises the normalsubscriber's telephone line that is "switched over"to the alarm system during periods of unoccupancywhen the alarm is in the active mode. The necessaryalteration to an existing telephone is simple and itis effected for a moderate charge. Auto-diallers anddigital communicators may utilise this method ofcommunication. Line faults, telephone trafficcongestion and deliberate "ringing in" by thirdparties may disable the alarm transmission. Animprovement upon this is afforded by an exclusive,ex-directory line barred for incoming calls, whicheliminates the disabling effect of "ringing in".However, this line will attract its own separatetelephone line account charges.

332. Where more than one telephone line entersthe school it may be possible to designate one lineas an outgoing calls only line. It could be used fornormal calls during the working day and switchedto the alarm system at other times.

Scan monitored exchange line

333. At the protected premises the normaltelephone line is permanently interfaced with asmall electronic outstation of a mainstationmonitoring scanner located in the local telephoneexchange. The subscriber may make full normal useof the telephone whilst the scanner silently checksthe status of the alarm system and telephone linecontinuity. In the event of a line fault or alarmcondition, the occurrence is electronically reportedfron the local telephone exchange by high integrityduplicated private lines to a secure computerinstallation located within the telephone network.From here, similar high security private telephonelines interconnect with a compatible, privatelyowned, computerised central control station.Normally the central control station will be ownedby one of the national alarm companies whosecomputerised monitoring will display theappropriate action to be followed in any alarm oralert condition. Usefully, other building servicesand engineering plant controls may alsocommunicate their status condition.

334. A variant on the above dispenses with theprivate central control station. A computerisedprocessor in a main telephone exchange will directthe signal to the police or other emergency service.Throughout the system, careful coordination ofalarm detectors and their related signals is essentialto ensure that appropriate alerts are directed to thecorrect emergency service. Naturally, the police areonly interested in genuine alarm condition reports

80

and further status monitoring such as opening,closing and general condition reporting require theservices of a private or LEA central monitoringstation.

335. Anyone proposing to enter into a contract fora proprietary communication system, as detailedabove, must assess the full technical features andthe extent of recurring charges. In respect of this, itshould be determined whether or not the telephoneline charges are incorporated in the recurringcharges levied by the monitoring company.

336. By virtue of the fact that the systemsdescribed here use the subscriber's ordinarytelephone line, scope exists for communications ofhigh security at a reasonable price. Futureinnovations are likely to increase the scope foradding the monitoring and control of additionalbuilding services.

D. ect (private) line

337. In most instances this will be the mostexpensive form of communication medium. Aprivate telephone line is permanently connected tothe alarm system. The line is continuously "live"eliminating the requirement for auto or digitaldialling.

338. This method of communication is most oftenemployed in high security applications where theprivate line is directly extended to a distantcomputerised central control station. Sometimes,the telephone line rental cost may tbe reduced whenit is possible to terminate at a local multiplexinterface extended by private long-distance wires.that are rented and operated by the owner of theremote central control station. In respect of this,some security companies have set-up their ownprivate wire networks and may include the linecosts in their overall monitoring charges.Accordingly, an assessment should be made oftelephone line rental savings against any additionalmonitoring cost charges for the use of themonitoring company's long-distance private lines.

Future communication opponunities

339. Technical advances and greater opencompetition in the communications sector willwiden the options by which intruder alarms may beextended to remote control centres. Furthermore,the full communication potential to remotelymonitor and control building services plant is yet tobe realised.

87

340. Before deciding which communicationmedium is appropriate for any application a fullup-to-the-minute technical appraisal is requiredtogether with an assessment of the long-termrecurring charges.

341. All equipment must be compatible with thesystem to which it is interconnected andaccordingly equipment should comply with therequirements of the appropriate communicationsauthority. As obsolete telephone exchangeequipment is replaced by microprocessor basedsystems the scope for advanced monitoring willincrease.

Sd81

APPENDIX 6 Central monitoring stations

342. When remote signalling equipment is used analarm signal may be automatically directed bytelephone line to a central monitoring station.Computers are invariably used at the central stationto translate the alarm signal onto VDU enablingthe operator to call the police or take otherappropriate action. It is also possible for non-alarmevents such as opening and closing times to bemonitored. The degree of sophistication is largely amatter of customer choice. Refer to BS 5979: 1987remote centres for intruder alarm systems.

343. This appendix describes the technical aspectsof central monitoring.

344. Central stations serve as the nerve centrefrom where direct contact is made to the police andother respondents to alarm signals. Their dataprocessing power can be used to provide a highlevel of technical and event monitoring to furtherimprove security. The effectiveness of a centralcontrol station depends upon the amount andquality of information transmitted between theprotected premises and the central control station.Accordingly, full system compatibility must beensured for the protected premises, thecommunication medium, and the required level ofcentral station monitoring. The entire, and oftenexpensive system, is only as good as its weakestlink.

Protected premises

345. It is essential to determine the optimumlevel of security attainable within cost limits. Localaudible alarms with or without a 999 autotapedialler may suffice for low risk, low value premises.

346. Central control stations offer a wide range ofservice options. The intruder alarm system shouldbe specifically tailored to the required monitoringservices. As a minimum requirement, the systemmust possess a digital communicator capable ofsignalling the premises identification code togetherwith an alarm signal in a format compatible withthe central station receiver and data processingfacilities. "Open" and "close" event signals canalmost be regarded as basic essentials. Alarmcontrol panels incorporating a computer based"intelligence", may enable individual detectormonitoring and other forms of central stationinterrogation. These controls may not be used to

82

full benefit unless interconnected to a central stationwith the data processing capability of performing allthe required levels of system monitoring. In respectof this, there may be a dependency upon a solemonitoring company thereby reducing futureoptions for competitive tendering of monitoringservices.

Communication link

347. Paragraph 330 "Remote SignallingCommunication Medium" details the availableoptions. Essentially, the method of communicationshould be compatible with the required level ofsecurity and be capable of carrying the requiredexchange of data between the alarm control paneland the central monitoring station. In high securityapplications the data exchanges may be made in acryptic form thereby imposing greater demandsupon the communication medium.

The central control monitoring station

348. The proprietors of central control monitoringstations are in the competitive business of trying toattract subscribers to occupy spare capacity withintheir microprocessing facility and multiplexed datalinks. With careful planning and coordination in theselection of alarm systems and communication linksit should be possible to possess the freedom ofchoice enabling the selection of a relatively low costmonitoring option. Also, LEAs as owners ofmultiple intruder alarm installations, cansuccessfully operate their own monitoring stationbased upon a single micro-computer and receiver.

349. Proprietary central control stations areconstructed to meet various approval requirementsand are generally located in high security premisesof a bunker type of construction.

350. The number of alarm systems that may bemonitored by a single central control station isvirtually unlimited, provided that physical spaceexists to extend computerised processingequipment. These hi-tech environments are virtuallypaperless and involve the minimum amount ofphysical effort by the control operator. Generally,the operating staff are engaged in routinemonitoring activities, and are employed in sufficientnumbers to respond immediately to an alarm

8 9

=MU LI 2008 i.

Fig. 23 A typical receiver that may beiMO

'D. Ig3 Il,,,

used to form the basis of a privatelyca a A _ I owned central station. In conjunction with

a microcomputer 3000 alarm system canWIF:gispr Allra Mak '14%-41.11% be monitored.

at

-

Fig. 24 A typical monitoring station owned and operated by a medium sized alarmcompany. Such a station may typically handle up to 10,000 alarm system with scopeto expand to 25,000 systems.

4.40

44111;040......... -

1111111111111111111

11111111111111\1

'Ir111111111111

9u

44,11

40,,

83

11"

Fig. 25 A typical central monitoring station owned and operated by a large nationalcompany. Stations like this may handle up to 500,000 alarm systems.

activation. However, every connected alarm systemis programmed to have priorities assigned todifferent alarm conditions and a computerisedqueuing system ensures that during exceptionallybusy periods events such as personal attacks andintruder detection take preference over events suchas "late to close" signals.

351. In response to a data transmission from theprotected premises alarm system, the central controlstation's computer produces a real language displayupon the operator's VDU. The displayed textinstructs the operator on his course of action anddetails telephone numbers to alert the local policeand relevant keyholders. Optionally, these telephonenumbers may be dialled automatically to conservethe operator's time. By carrying out a simplekeyboard operation the operator is required to logand record his actions. Where expanded monitoringoptions are utilised, fire and plant failure alerts maybe advised to the central control station andsubsequently relayed to the relevant respondents bytelephone.

352. Where an intruder alarm system condition

84

monitoring is incorporated, technical informationsuch as near false alarms or detector performancedegradation is temporarily stored and reported tothe service engineer. Often a hard copy print-out isissued.

353. By necessity, the modus operandidescribedhere is in general terms. Intending users of centralstations should ascertain for themselves thecompatibility of the services offered to their ownalarm system and security needs. Figures 23, 24

and 25 show the range of central station options.

354. Where owners of multiple intruder alarminstallations establish their own monitoring centralstation, scope exists for the efficient administrationof the alarm systems. Optional software enables themonitoring micro-computer to control service visits,raise repair and maintenance orders and furthercontrol invoice authorisation. Continued softwaredevelopment is likely to extend this range ofadministration facilities. A micro-computer with a40 mega-byte hard disc may handle up to 3,000

separate alarm systems.

91

GLOSSA IT

Hertz (Hz)

Ultrasonic frequency

Doppler effect

Masking

Reed contacts

Absolute zero

Absolute temperature

Trap protection

Walk test

Shunt out

Zone omit unitsPIR

Quad

Multiplex

Fresnel lens

Multi path reception

Catenary wire

SI Unit of frequency.Previously referred to as cycles per second.

Frequency of mechanical vibration above the range audible to the human ear.

Apparent change in frequency of sound, light, or radio waves caused by relativemotion between the points of transmission and reception of the radiated waves.

Disabling of a movement detector by positioning a physical object to shield thedetector's sensor or receiver from the intended field of coverage for motiondetection.

Electrical contacts located at the ends of reed like strips of springy metalgenerally enclosed in a vacuum envelope. Under the influence of magnet, thecontacts may make or break contact.

A theoretical temperature equal to minus 273.15°C.

A scale of temperature measured from absolute zero.Note: 0°C = 273.15K. A unit degree Celsius is exactly equal to a unit degreeKelvin.

Detectors installed strategically in circulation areas to restrict undetectedmovement throughout a protected building.

Slow walking to establish range of detection. Generally, a light on the detectorilluminates when movement is sensed.

Partial disarming of an armed alarm system. Generally provided whenoccupancy is required to a limited area of a building.

Proprietary key operated devices to shunt out an alarm circuit.

Passive infrared detector.

A term applied to a PIR detector where two, dual element sensors are used todivide each detection zone into four segments.

Electronic circuitry or equipment capable of handling a multiple am6unt ofdata.

Flat optically worked plastic. Alternative to conventional lenses.

Signals receiired from more than one direction, usually as a result of originalsignal being reflected off physical objects.

Wire of high tensile strength use to support electric cable between two points ofsuspension.

Printed in the United Kingdom for Her Majesty's Stationery Office Dd 289052 7/89 C50 398/2 12521

85

92

n ruer a arm sys ems can e very. e'ec ive in reucingincidents of break-ins and thefts. However, to be effectivethey must be

correctly designedproperly installedsensibly usedregularly maintained.

If there are weaknesses in any of these aspects, thesystem will not operate properly and be susceptible tofalse alarms.This bulletin offers advice on specification, installationand maintenance of intruder alarm systems. It describesthe operation and application of various types ofdetectors and other components used in the systems.The bulletin also contains case studies of goodinstallations in schools.

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