Alarm Detection Devices.

A Brief Explanation of what each Device actually does.

The Door Contact (Magnetic Reed Switch)

Commonly reffered to as a Door Contact but Known in the trade as an MRS (Magnetic Reed Switch) this device simply lets the alarm control panel know if a door, shutter or window is open or closed. They come in all shapes and sizes to suit the door/window and frame to which they are being fitted and have an operational gap from 15 up to 60mm dependant upon type. These are nearly always fitted to any external doors in the premises, but can be fitted to any door or window that requires security.

The Panic Button (PA Button)

When placed in a good location these Devices can prove a useful addition to your alarm system. Ideal locations for the hardwired devices might be by the front door, or within reach of your bed. You could also ask for the wireless pendant type which you could wear around your neck, and when pressed would work from anywhere within your property, these can have up to 100 yards range so would be handy to have while gardening for instance.

The Shock Sensor (Viper)

Quite simply this device detects shocks, and is used to hopefully detect an attempted break in by forced entry. The idea is that the shock sensor detects any vibration caused by the intruder trying to gain access and triggers the alarm system before he has actually got in. A worthwhile consideration for any door or window frame.

The PIR (Passive Infra Red Sensor)

The Passive Infra-Red sensor. Well when used correctly these detectors are in invaluable asset to any alarm system, they detect movement of heat, by looking at the room in Infra-red. The detector lens splits the room up into 20+ areas and basically any movement of heat between these areas will cause an activation of the alarm system. Their are several variants of this detector and the most common are listed below.

1. The Standard PIR is as described above.

2. The QUAD, is basically two Standard PIR detectors working together in one unit. The effect is much better reliability as both the detectors need to trigger at the same time which creates a higher resistance to false alarms. Most reputable companies fit these detectors as standard.

It should be noted that many manufacturers who claim their detector to be a QUAD are in-fact misleading, since they do not have the two inputs connected to two independent PIR channels, they simply connect them together through the one channel, which reduces their so-called QUAD to a DUAL detector. Its a very dishonest practice in my own personal opinion and in think installers should be made more aware of it.

3. The DUAL-HEX detector, (this is patented by Guardall and used in the V12 and V12AM detectors). It actually has 12-detection pads (not 4 as in a quad) arranged in a near symmetrical pattern. This allows PHASE processing of the target to a much higher level than a Quad - which allows many more common false alarm sources to be processed out.

4. The DUAL-TECH, this is two different technology detectors built into the same unit. You get the benefits of a standard PIR sensor and also a microwave movement sensing device. False alarms are almost impossible with these detectors. They simply don't trigger unless something has moved. These detectors work great even in the harshest of conditions, such as a garage or shed where the environments they are protecting can change on a daily basis. You can also get a pet immune sensor based on this technology.

The Beam Type Detector

The Beam Detector is best used when detecting movement across larger areas. They typically have ranges from 20 meters up to several hundred meters. They normally have separate transmitter and receiver units, and movement is detected by something crossing the beam created between the units.
These can be used externally to monitor the perimeter of a premises. A set of such detectors could actually be used to monitor a several hundred meter perimeter using a few correctly placed reflectors or mirrors.

The Glass Breakage Detector (BGD)

Ideal for usage in areas with several windows, or perhaps conservatories. These detectors are really single room devices, and not specified to frequently by installation companies for residential use, but they are good and useful detectors which I think should be considered more often. They trigger when glass is broken by selectively monitoring a range of audio frequencies through a microphone. A downside to this type of detection is that other things (such as a can being kicked along a pathway) can generate noises in it's detecion range which may also trigger the alarm.

The Smoke / Heat Detector

Smoke detectors are an invaluable addition to any Alarm System so long as they are correctly placed. Most houses would perhaps only need a couple (one in the Hall, and one on the Landing). Heat Detectors are perhaps best situated in the Kitchen, and possibly the lounge.