Features of Different Types of Alarms
Most home owners who want to install an alarm system will want it to help prevent unwanted intrusion and theft through burglary. Any burglar alarm is in its basic form designed to detect intrusion and raise an alarm. There are three main ways in which this is done:
• detection of motion
• unauthorised opening of windows or doors
• visual detection of intrusion through cameras
Intrusion and unexpected motion can be detected through motion detectors signalling movement to a base unit, sensors on doors and windows signalling that they have been opened, or remote cameras sending visual evidence of intrusion.
Monitors, sensors and cameras can be linked to base units either by ‘hard wiring’ or wirelessly. Most base units will be wired to the premises’ electrical system but will also have back up from an internal battery ensuring they continue to function in the event that electrical supply is cut off either accidentally or intentionally.
Notification is the term used to describe what the alarm system does when it detects intrusion. Notification can be by siren, an audible alarm that alerts occupants, neighbours and passers by that the system has been activated. These are termed ‘Audible only’ systems.
As well as raising a localised alarm systems are available that notify a nominated person or company by telephone or text messaging; these are called Speech or Voice Dialler systems. The nominated person or company will hold a key to allow access to the premises on which an alarm has been raised. Both landline and mobile telephone networks are used.
More sophisticated is an Alarm Transmission System that broadcasts signals by radio and/or telephone to a continuously monitored receiving centre that then contacts specified persons and key holders. These are known as Monitored Alarms. Some of the options available for this type of alarm also contact Police.
Surveillance systems are typically a system of remote-controlled cameras linked by cable or wireless to a receiving unit that displays the visual information. This is monitored and evaluated by an operative who then makes a decision as to what action should be taken.
Surveillance cameras can be added to a burglar alarm system to allow occupants to visually assess any callers or intruders.
Fire alarms use smoke and heat detectors to raise an alarm when fire is detected. There are three different types of detectors normally used with fire alarm systems:
• ionisation detect small smoke particles
• optical detect larger particles
• heat detect increase in temperature
These detectors are linked to a base unit which sets of an alarm.
Most homes will now have smoke detectors either built into the domestic electrical system or added. Detectors can be hard wired into the electrical system with back up power from a battery in case the electrical supply is interrupted, or can be ‘stand alone’ units mounted on ceilings and powered by a battery that needs to be regularly changed.
It is worth remembering that a thorough risk assessment should be undertaken before any choice is made regarding which alarm is best suited to any premises. These assessments are very often carried out by companies that supply alarm systems.