A guide to intruder alarm systems

Intruders gaining access to your home can be a terrifying prospect. It's bad enough if you're out when it happens, but even worse if you're in, maybe upstairs asleep. In this article we briefly outline the options available to homeowners wanting to install an intruder alarm to improve their home's security.


  • DO get your system professionally (use of NSI/SSAIB registered alarm companies is advised) designed, installed and then regularly serviced.
  • DO get into the habit of setting your alarm whenever you go out, and ideally ‘part set’ it when you are asleep
  • DO check, between service visits, that alarm sensors are not damaged, and that movement sensors are not obscured by dirt or objects placed by them.
  • DO check (via a ‘walk test’ that activates the sensor LED indicator) that movement sensors continue to pick up moving persons at their expected range, as they can fail/deteriorate with age
  • DO keep spare batteries to hand for wireless devices
  • DO keep any keyholder details (stored in the system or at an ARC) up to date, especially when you/they may be on holiday, or they become unable to act on your behalf, e.g. due to illness
  • DON'T leave details of alarm operating codes or spare unsetting devices by the control panel, or in insecure areas of your home
  • DON'T let pets into areas protected by alarm movement sensors
  • DON'T ignore (annoy any neighbours) false alarms. If your system creates false alarms it needs checking, repairing or re-designing

What different types of intruder alarm systems are available?

Alarm systems come in various forms. At their simplest they may be battery powered (temporary) systems that may prove useful for protecting a shed or outbuilding. More usually they are permanently installed and powered from mains electricity with battery back-up. Whatever its basic type, all alarm systems will essentially consist of a series of detection devices connected to an alarm control panel, either by wires or (increasingly in homes) by wireless links and a means of alarm ‘notification’.

Alarm systems have various options for notifying someone of an alarm activation, the intention being to bring someone to a premises to head off/stop, and thus limit the effects of, crime and otherwise re-secure them.

The most basic form of notification is the activation of a warning device (e.g. a siren) on site, but unless someone is present to hear and respond to ‘such ‘audible only’ alarm systems the benefits are limited. Whilst most ‘audible only’ systems can be connected to simple devices (speech diallers or home security APPS) that can send messages (voice, text, e-mail, etc.) to home owner’s, or nominated ‘keyholder’s’, home &/or mobile phones such systems do have drawbacks. To be truly effective, alarm systems should be connected by an Alarm Transmission System (ATS) that uses landline &/or mobile phone links to connect your home to a permanently manned Alarm Receiving Centre (ARC) who will ‘remotely monitor’ your system.

There are lots of different ATS available, the main difference between them being how quickly/reliably they can alert an ARC to a lost connection. We recommend use of ‘Grade’ 4 ATS, as these alert an ARC to such issues within 3 - 6 mins; but ‘grade’ 3 and 2 ATS are often promoted which may be cheaper, but can take 5hrs or 25 hrs, respectively, to self-report failure.

An ARC will retain phone contact numbers of the home owner and keyholders, and then seek to alert them to any activation or system fault. If certain criteria are met as to the nature of the alarm system, its installer and ARC, an alarm system can be allocated a Police Unique Reference Number (URN) - which permits the ARC to ask the police to attend in the event of an alarm activation that qualifies for routine police response.

Who should fit an intruder alarm?

Whilst use of DIY fitted alarms may be tempting, any system that is being relied upon to provide good security should be designed, installed and then maintained by an alarm company on the approved list of one of two bodies, i.e. The National Security Inspectorate (NSI) or the Security Systems and Alarms Inspection Board (SSAIB). This not only helps ensure adherence to applicable British Standards and Police requirements, but also means they are insured, are subject to annual audits, employ staff subject to criminal record checks and participate in a formal dispute resolution service. It will also mean that the value of you alarm system is more likely to be recognised by your insurer.

Cost of installing an intruder alarm

This varies enormously, reflecting the type/sophistication of the required system and the size of a home. Whilst a DIY fit basic wireless alarm can cost as little as £200 - 500, you should expect to pay £800 – £1500 for a professionally fitted ‘audible only’ system and in the region of £1500 - £2500 for an ARC monitored police response system. For the latter monthly/annual monitoring fees are also levied.

Is it worth just getting a ‘dummy’ alarm box?

The short answer is generally ‘no’, as criminals can usually tell the difference between a working alarm system and a non-working siren ‘box’ simply installed on the outside of your home.

What detection devices are available?

The most common form of detection devices used nowadays are magnetic door contacts, which activate when a door is opened, and movement sensors, which pick up movement in an area. The most common form of movement sensor is a Passive Infra-Red (PIR) detector which detects movement of a warm object such as a human being but may, if too sensitive/located in wrong area, pick up warm air from heaters/sunshine on windows and the like. To help limit false alarms Dual Technology movement sensors are increasingly used, these containing both a PIR and Micro-Wave (Radar) detector, both having to be tripped before an alarm signal is sent.

Manually operated Hold Up Alarms (HUA) are often also fitted.

How do I identify ‘at risk areas’ in my home?

A competent alarm installer will help you do this, and for certain types of system ‘regulated’ installers are required to carry out a formal security risk assessment to help them design an appropriate system. To do so, they will need your co-operation in disclosing information about your valuables, habits and expectations – all the more reason to use an knowledgeable, honest and reliable ‘regulated’ provider, e.g. an NSI or SSAIB listed alarm company.

That said, in general you should look to provide suitable detection at, or close to, all possible legitimate/likely forced entry points to your home. This will typically involve fitting alarm contacts to perimeter doors and movement sensors nearby and close to externally accessible windows.

What alarm ‘extras’ are available?

Most alarm systems permit the connection of additional devices to a system, such as water leakage and fire detection devices. Social alarm devices may also be available, e.g. as used by some elderly/vulnerable people to call for assistance – typically via a worn pendant device/switch. However, these are more usually installed as stand-alone systems.

CCTV images can enhance security at many homes, and it is increasingly possible to connect CCTV cameras/systems to intruder alarm systems and transmit images elsewhere for viewing/response. Note. Cameras that view other people’s property or public areas may contravene The Data Protection Act and related guidance issued by the Information Commissioners Office (ICO), see https://ico.org.uk/for-the-public/cctv/

Where can I get more information on alarms?

Part of Aviva (Aviva Risk Management Solutions) undertakes security (and other) risk surveys for some of our customers and maintains a library of information sheets on many risk control topics, including intruder alarms. This library is available to view/download from the ‘Knowledge Store’ tab at http://www.aviva.co.uk/risksolutions/

Bodies like the NSI and SSAIB also have website based information, see www.nsi.org.uk and www.ssaib.org



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