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Techniques: Burglar Alarms for Guarding Your Garage

We've talked about security before, but after a spate of thefts David Atkinson offers a timely technical guide to alarms and how you can best use them to safeguard your classic bike...

The following article is written with the best intentions. Whilst I know exactly what I am trying to tell you, if anything is unclear please ask for clarification as I may be too technical in my terminology here and there.

No doubt many of you keep your pride and joy in damp and draughty sheds and garages, and possibly have more than a few worried moments on how it should be protected. One option is the installation of a burglar alarm and that is not as difficult as might be imagined, but they should be installed to BS4737. The notes below will also allow you to install one in your home as well. It will not make you into instant experts but the installation should be within the realms of anyone capable of tinkering with a motorcycle.

You are not allowed to have police calling systems on a self-installed basis and anyone requiring or being told by their insurance company that they have to have one would be best advised to contact a reputable company by way of Yellow Pages. A service agreement would then have to be entered into. I would also suggest a bona-fide supplier as opposed to the local DIY shop. Believe it or not, but I have been shocked at the prices charged by the multi-nationals as opposed to what I can buy the equipment for.

There are many abbreviations used for equipment within the industry and initially I will try and identify them with their abbreviations and various anomalies.

They're watching you right now... Above, clockwise from the right:

  • Passive Infra Red unit, PIR. Not ideally recommended for garages or areas where draughts and quick temperature changes can take place
  • Shockguard. May be fitted to walls and window frames. This unit can be adjusted to operate in varying types of environment. This detects attempts at intrusion, ie chipping through walls or breaking window frames. It is not necessarily proof against intrusion through a door being opened if used solely on its own and not in conjunction with a door contact
  • Dual Tech Unit. This has the joint Micro-Wave and PIR technology built in. These are better suited to garage applications but do tend to cost more than PIR units


    Magnetic contacts are, as their name implies, contacts which use a magnet within close proximity of the contact. This is to attract the reed switch within and contrary to many opinions they do not have to touch in order to work. There are various types of magnetic contacts; the concealed type is, again as its name implies, concealed. These are normally used in houses and never on outward opening doors. Surface contacts are normally used on shed, garage or outward opening doors and are more robust than the concealed type. Roller shutter contacts are normally aluminium. and are used on large roller shutter doors, up and over type doors or generally doors which may not be as snug fitting as the average house door. This type of contact is normally waterproof and capable of being driven over without being damaged.


    Passive Infra-Red or PIRs. These do not, as is often thought detect movement but work on a variation in ambient temperature, either up or down within a designated period of time. They are non-adjustable for range but some types allow the lens to be changed so as to give a different type of coverage, ie fan shaped beams, curtain type beams, corridor beams etc. They normally start with a range of around eight metres upwards. These I would never recommend for use in a garage due to the invariable amount of draughts that blow round the entrance doors and under the eaves.

    Dual-tech Units

    These are a passive infra red unit incorporated with a micro-wave unit. These pick up heat and also movement. The theory being that if a draught, which would be capable of activating a PIR was present, the movement side would not be there and the micro-wave unit within would not false alarm. Conversely, if something fell over in the garage, the movement side would activate and there would be no variation in temperature. The PIR side would then stop the false alarm. This type is what is best suited to a garage environment. The micro-wave section is adjustable for range and this is due to the fact that gases in fluorescent lighting, running water in plastic rainwater pipes and glass are capable of being penetrated by the micro-wave beam.

    Self-actuating Bell / Siren

    Often referred to as an SAB. These units, unlike their portrayal in films, have a permanent power fed to them and will sound if pulled off the wall or the feed wire is cut. They are triggered by a command from the control unit and are only allowed, without special dispensation, to sound for a maximum of 20 minutes. This is due to the pollution by noise act, but they can be adjusted to ring for a lesser period of time if required.


    Normally a six core flexible cable, although many people run an eight core cable so as to save doubling up on cable runs. One thing that throws many people is the fact that burglar alarms are series circuits NOT parallel as in house wiring and lighting circuits on cars and motorcycles. The voltage is a nominal twelve volts and the wiring is not allowed to run in the same conduits as normal mains wiring. Circuits should ideally be as few detectors as possible per circuit and never more than one space detection unit per circuit, nor should space detection be mixed with contacts.

    Control Box or C/U

    These range from various cheapies that control a few circuits up to very expensive multi-processor units that can manage a few hundred circuits. They are powered from the mains with a step down transformer and battery back up which must be capable of managing an eight power failure.

    Don't write the code number of the back of the door. A polycarbonate digital control unit. (There are many companies engaged in the manufacture of alarm equipment and this photograph is not intended to show bias to any particular company!). They all have emergency standby batteries that are on a permanent trickle charge, which have to give a minimum of an eight hour standby time in the event of a power failure.

    Siting of the units is normally down to where it will fit best, but PIR units or Dual-Tech units should not look towards a window if it can be avoided. Likewise do not site them above a radiator. They are best sited in a corner, they have a minimum of a 90-degree angled beam, and if looking into a room from a corner then maximum coverage will be achieved. A rough rule of thumb that I used to work to was: if I can't see the unit, the unit can't see me. So don't store things in front of them.

    When installing the alarm system, most garages will probably have only a side entrance door and a main door. I would then suggest that the protection be: one dual-tech unit, one small surface contact and one heavy duty contact for the main door. Remember that if you have conventionally opening doors they are invariably rebated so only the first opening door needs to be alarmed. The control units are capable of being programmed to allow normal entry and exit without an alarm sounding, and the space protection unit would be on what is termed 'walk through'.

    You may now think 'how will it function if they break the door down?' The answer is: it will only be on walk-through until the entry time runs out and it will then alarm. If however entry is gained through perhaps the roof, window or perhaps a door other than the normal entry door, there will be an immediate alarm.

    For those with multiple sheds, a larger alarm could be used with controlling keypads in each section which only turn off the section that is in occupation. If you are connecting to an existing house alarm, all cabling should be within what is classed as the protected area and if it means an external run, then it should be in conduit. It is also possible to use a single circuit on a house alarm to control another alarm in the garage which would then operate the main alarm.

    They are only door contacts. Don't be alarmed. Above, clockwise from the right: Door Contacts. Varying types showing concealed, indoor applications, pencil type, again indoor and requiring a junction box for connection, small surface, suitable for outward opening doors and garages. Brown version for the colour conscious, white concealed showing size, 20mm diameter bit needed for hole. A larger type of surface contact for up and over doors. There are also heavy duty aluminium contacts for floor fixing

    Those of you in the unfortunate position of not having a mains supply need not be too downhearted; there are radio contacts which will transmit to a receiver within the house or point decided for the installation of the main control unit. Unfortunately there is not, to the best of my knowledge, a radio transmitted dual-tech unit. There is however a radio PIR and the batteries normally last at least a year and will signal when their batteries require replacing.

    This summary is just the tip of the iceberg regarding alarms and every case should, ideally, be looked at individually. There are external alarms, which can cover the approaches to your garages. There are also units that, if connected to a telephone line, will call telephone numbers of your choice and play a message, also of your choice. These can also call mobile numbers and if the first number chosen does not answer they will try another designated number. If there is no reply on any of the numbers it would be as though you had an audible only alarm. These units are allowed to be installed without a service contract but they must never be programmed to dial 999.

    The average material cost for an alarm system like the ones I've described should be less than 200 plus VAT. This would be for good quality equipment which would be capable of being used on both domestic and industrial premises. You may also fit smoke detectors or, because of possible dust pollution, rate to rise heat detectors. These would be on 24 hours a day, irrespective of the alarm being set or unset.

    Good luck everyone.

    Triple Exemption. I like the sound of that. Self actuating bell/sounder incorporating a strobe lamp. These now have to cease sounding after a maximum of 20 minutes. This is under the Pollution By Noise Act. Motorcycle exhausts are exempt, especially triples...

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