The Circuit

Home Security Systems are a simple electric circuit. To open or close a light, you simply throw a switch. In a burglar alarm it?s the same except the switch detects the movements of the intruder such as the opening a door or window.

Two categories

In a closed-circuit system, the electric circuit is closed when the door is shut. This means that as long as the door is closed, electricity can flow from one end of the circuit to the other. But if somebody opens the door, the circuit is opened, and electricity can’t flow. This triggers an alarm.

In an open-circuit system, opening the door closes the circuit, so electricity begins to flow. Also in this system, The Alarm is triggered when the circuit is completed.

Magnetic sensor
A magnetic sensor in a closed circuit consists of a few simple components.

- a battery powering a circuit
- a spring-driven metal switch built into a door frame
- a magnet embedded in the door, lined up with the switch
- a separately-powered buzzer with a relay-driven switch.

Control box

The control box is hooked up to one or more alarm circuits, but it also has its own power supply. Once the alarm is triggered, the control box won’t cut it off until somebody enters a security code at a connected keypad. In most installations the control box is kept in a veered place so that the burglar can’t even think of disabling it then the alarm goes off.