How Does Burglar Alarms Work



Wired alarms are almost extinct. Wireless burglar alarms operate by either of the two means, today.

1.Connected by radio frequency

2.Connected by infra red light rays

Wired systems required power to operate continuously unlike the wireless alarms which run on battery power. There is the third type, which combines the features of the earlier two and is known as hybrid alarm.

Burglar alarms operate on simple principles. When their ‘connection' or circuit cuts, they get triggered. When intruders pass between two sensors or a door opens it is detected by their cut circuit.

Normally there are 2 types of circuits; open circuit systems and closed circuit systems. Let us not get into jargons and cliché words; closed circuit operates when the door is closed as electricity begins to flow. But when interrupted by opening doors, circuit also opens and the alarm goes off. And it is the exact reverse of this in open circuit alarms. The siren is triggered when doors are closed.

Closed circuit alarms are first choice for front doors for the fear of wiring being cut by burglars.

How does a sensor work, after all? In a wired system, a magnet pulls the spring loaded switch to close circuit when door is closed. When the door opens, spring retracts causing the circuit to break and triggering the alarm. The principle is same for wireless infrared system too. In place of magnets and wires, there are infrared sensors and emitters. If sensors don't sense infrared light for reasons like opened door or other obstructions, the circuit is broken.

Burglar Alarms are also useful in protecting cars. FM radio based car alarms are getting popular because of their simplicity. They have a two part system: a transmitter, fitted to the car and a receiver which can be out side the car (home or office). The receiver makes noise when burglars move the car a few meters out of your porch. If the wireless alarm (transmitter) is disconnected from battery, remote alarm still remains activated because the receiver still continues to make noise. So this type of burglar alarm is highly reliable.

While installing, ensure you follow specified codes by insurance companies or certify it by third parties like Underwriters' Laboratory etc. After all, you need someone even after burglar alarms are breached.