Appliances Renovation

Digital Home Security System, Do all it yourself (Control panels, Detectors, Monitoring)

Control panels

There are no specific British Standards for control panels (or alarm devices themselves), although elements of BS 4737 relate to features found in alarm equipment. This is likely to change with the introduction of European Standards which will, for the first time, require individual components to meet levels of performance and construction.

It is very important to understand how an alarm system is operated if false alarms are to be avoided. To reduce this risk, manufacturers have been making instructions easier to follow and many panels now incorporate a Liquid Crystal Display (LCD) giving plain English step- by-step instructions to guide users through the arming, resetting and disarming procedures.

Precautions to prevent tampering are also built in. The control panel should incorporate an anti-tamper device to deter anyone from trying to prise the lid or attack it in any way. Each zone, the wiring and detectors will also be protected from attack, triggering the alarm if there is any interference with the system.

The control panel will also feature a device to set the alarm and turn it off. This may be a keyswitch (operated by key only) or a keypad, where you will need to use a code (usually four digits) to carry out any procedure.

Most panels allow you to divide your home into zones and set all or part of the system. It will also enable you to set the entry/exit time delay. This is the amount of time you have to enter and turn off the alarm or set the alarm and close the door behind you. It will vary but can be as little as two seconds to over a minute.

Make sure it is set to give you enough time to enter or exit the front door (or your final exit) and disarm/arm the system. The delay will be signalled by a sounder and can instill panic if you have forgotten the code or can’t find the key to turn the panel off before the alarm sounds!

The panel will also contain an alarm sounder of its own and should have a 12v rechargeable stand-by battery to take over powering the alarm, for at least eight hours, in case of a power cut. If a primary battery is used as a stand-by, it must be able to run the system for four hours to comply with BS4737. If this runs out, however, it will trigger an alarm condition.

The alarm panel will operate using a 230v mains supply — you should never see a professionally-installed wired alarm panel with a plug attached. It should always be wired in. In addition, alarm panel cabling and existing mains wiring should never be run in the same trunking.

The trend today is to have the control panel hidden away, perhaps in a cupboard, where it is out of sight and not immediately accessible to an intruder. The system will have one or more remote keypads positioned at prominent places around the house which can be used for all the day-to-day programming . Usually not much larger than a light switch, they provide an attractive and discreet system which is relatively easy to operate.

Detectors

The most popular type of detector to protect complete areas — rooms and hallways — is a passive infra-red device (known as a PIR). Also essential to the system are magnetic contacts (small, flush or surface-mounted devices which protect doors and windows) and one or more personal attack buttons which activate the alarm in an emergency even when it is switched off.

Personal attack buttons usually have a red circular or rectangular push button which triggers the alarm and can only be turned off with a special key.

Other devices used may be ultrasonic or, rarely used alone in domestic situations, microwave. Some detectors now combine two of these technologies, typically PIR plus microwave, in an effort to reduce false alarms, and these are proving very successful in difficult environments.

A very important addition to an alarm system is a smoke alarm. There are smoke detectors which can be wired into an alarm system (the latest Building Regulations specify smoke alarms as a standard requirement in new and newly converted homes) or you can buy a battery-operated smoke alarm, easily fitted.

Monitoring

Most modern panels are able to provide a means of monitoring the alarm. A special device called a digital communicator is installed in the control panel and is able to send a digitally encoded signal, via a normal telephone line, to the central monitoring station.

For an alarm to be acted upon and a message to be passed to the appropriate emergency services (police, fire or medical), the receiving equipment must receive and acknowledge the correct sequence of signals.

Bells and sounders

The bell box can be of polycarbonate or, for high security applications, produced in aluminium and treated steel and powder coated. (BS4737 requires the housing to be of 1.2mm mild steel, 1 mm stainless steel, 3mm polycarbonate or equivalent.) Bell boxes should be fixed as high as possible on the house front and may now include a strobe light which will continue to flash after the bell has stopped ringing after the statutory 20 minute maximum period.

The alarm should also trigger if the bell box is tampered with. This is caused by a self-actuating bell module (SAB) which, if the mains cable is disconnected or cut, will bring in its stand-by battery to sound the alarm.

Bell boxes are also increasingly being fitted with a separate timed cut out (from two to 18 minutes approximately) so that if the SAB takes over operation of the sounder, it does not continue to ring, unless automatically reset by the system, for longer than 20 minutes at a time.

There is a good reason for this. If an alarm is considered to be constituting a statutory offence under The Environmental Protection Act (Section 80), local authorities have the power to fine the owners of the alarm up to £5,000. The Noise and Nuisance Bill increases these powers to enable officers to enter premises under certain conditions.

In addition, the London Local Authorities Act can oblige owners of offending alarms to fit cut off devices. This applies as much to DIY systems as to professionally installed ones, so beware.

As well as being fitted with anti-tamper devices, bell boxes may also have an anti-foam device which activates the alarm if foam is pumped into the box through the louvres at the side. Some bell boxes are being produced without louvres which also overcomes the problem.

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