From 20$ do-it-yourself kits to high tech security systems that need to be installed by professionals, alarm systems are all build around the same few basic concepts.

We will try to examine these concepts and as you’ll probably see the most simple and cheap burglar alarm systems are also the most effective. Usually the basic burglar alarm system is a very simple electric circuit that is built into an enter way.

In a burglar alarm the “switch” detects the act of intrusion such as opening a door or a window.
The magnetic sensor in a closed circuit consists of only few components , the most basic design usually has:

•    a battery to power the circuit
•    a spring-driven switch built into a door
•    a magnet in the door lined up to the switch
•    a separately powered buzzer

When you close the door the magnet closes the switch and the circuit is complete but the buzzer circuit stays open, if you open the door you move the magnet, the springs snaps the switch back in it’s position. This cuts of the current and sounds the alarm.

There are two types of circuits usually used when building an alarm system : a closed-circuit system and an open-circuit system. Closed-circuit systems are usually better given the fact that a crook can deactivate it by cutting the connected wires.

Some cheap burglar alarms use a button as the switch . The button is embedded in the door frame , when someone opens the door the button is realesed changing the circuit and causing the alarm to go off.
All of these circuits guarantee the security at the points where a burgler can enter the building but let’s see what we can do if he manages to pass trough the door alarm.
To detect an intruder who’s already inside the house you need a “motion detector”.

Basic motion detectors are common these days and also reasonably priced you can see them every day at shops doors for example.

In typical cheap burglar alarm systems however the control panel wont sound the alarm immediately to give the owner time to go and enter the security code. If the security code is not entered tough the control panel will activate the alarm.

There are few things security systems usually do when detecting an intruder such as activating:
•    flashing outdoor lights
•    a siren
•    a telephone auto-dialer that can either dial the police and play a recorded message giving them the address either dial the security company that will have information the information and call the police.

Home security industry is growing constantly and the competition between companies now made the prices drop, even a cheap burglar alarm system that can cost no more then 100-200 $ can be a good protection for your home.

To find out about specific alarm systems check with your local sellers.

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