Burglar alarms are used in houses, banks and shopping centers etc. There are numerous varieties of burglar alarms but they all are designed to do the same job. The main components of a alarm system would be a sensor, a camera, a motion detector, a buzzer a flash light and batteries.

Sensors
It is a component that is usually used to detect noise or a movement. Sensors are usually connected to the circuit. As soon as it detects the slightest noise or movement it initiates the circuit which results in triggering the buzzer and the flashing light.

Cameras
The camera as everyone knows, it is a gadget which is used to take a snap or video. You must be wondering why this is used for an alarm. Cameras help to show who and how many of them have broken in and hence resulting in identifying the burglar with ease.

Motion detector
This detector sends out bursts of ultrasonic sound waves and then waits for the reflected energy to bounce back. If there is no one interrupting the signal, the radio energy will bounce back in the same pattern. But if somebody enters the area, the reflection pattern is disturbed and the alarm sounded.

Buzzer
Buzzers are devices which are used to alert people that something has happened. These are set off as soon as the sensor or motion detectors give the signal to the circuits that something fishy is happening.

Flashing lights
These are powerful lights which flash in order to signal people that something is happening.

Batteries
Nowadays burglars are so professional that they do everything under the sun to burgle, they sometimes cut off the electricity so that you'll not be able to see them and to deactivate the alarm but with improved technology and the use of Batteries it makes it impossible for them to switch off the alarm. Even when the current is turned off your bugler alarm still functions.