Working principle of Burglar Alarm

The burglar alarm is one of the most reliable means to secure a house or a work place. It is becoming more and more popular among the homeowners because of the consistency with which it performs. Today, there are different types of home security systems available in the market and they perform in different ways to detect potential intrusions.

What is a burglar alarm?
Basically, the burglar alarm is a device that monitors the designated area or areas to detect the presence of suspicious elements. The system takes the help of the sensor to detect such elements. Once found, the system sends emergency signals to the user or to the monitor station if the user so intends.

The components of Burglar Alarm

The security alarm system generally consists of a number of elements that work together to enhance the security of a place. The basic components of a burglar alarm system are:

  • Control panel
  • Keypad
  • Sensor
  • Siren
  • Flashing light
  • Motion detector

How the entire system works?

The work of the home security system begins with the sensors and motion detectors. These devices are installed in different places that they monitor in their own ways. However, they send emergency signals to the control panel once they detect something that surpasses their tolerance level.

The control panel of the system works like the brain and decide the next step of action. Basically, there are two different things that the control panel performs. It can set off an alarm located near the house to alert the homeowner and the neighbors.

However, if the system is monitored from a centralized station, the control panel will send signals there without setting off any audible alarm. In the basic models, the control panel uses the standard telephone line to send the security message. However, some of the latest models do use the GSM and internet to dispatch signals. So, they don't need any wires.

The keyboard provided with the home security system enables the users to arm, disarm and program the security system according to their wish. Most of the time, users are given multiple keyboards so that they don't have to rush from one place to another to find the keyboard in emergency.

Burglar Alarm Working

Sensors of the Burglar Alarm

There are different types of sensors used in the burglar alarm system. Some of them are used outdoors while others are suitable for indoors.

Indoor sensors:

PIR: The Passive Infrared (PIR) sensors are very commonly found in most burglar alarm systems. It is passive in the sense that it captures the heat emitted from the objects. Therefore, it needs a clear sight of vision. As human body emits more heat, the sensor can detect the presence of intruders.

Ultrasonic detectors: These sensors send ultrasonic sound waves and receive them as they bounce back from the fixed objects in the room. So, if any object moves the wave length changes and the sensor detects moving object.

Microwave detectors: This type of sensor emits microwaves and detects discrepancies in the signals through the receiver.

Photoelectric beam systems: These sensors also emit infrared light beams. However, they observe whether there is any obstruction in its way.

Outdoor sensors:

Vibration sensors: These sensors are mounted on walls or other structures. They detect any vibration that occurs when that structure is attacked.

Passive magnetic field detection: These sensors can be buried and it monitors the area with the help of electro-magnetic field.

E-field: These sensors too, work in a similar fashion; however they are more programmable and can provide vigilance up to 4 meters of height.


There are different other types of sensors available for the burglar alarm systems. However, the users must consider their pros and cons to find out the sensor appropriate for their specific needs.


  1. Leonard Emeka, 17. May 2012, 10:40

    Can i build burglar alarm without sensor? If possible, can I have the schematic diagram and the operational principle?

  2. admin, 17. June 2012, 22:06

    Hi Leonard,

    You can not build a burglar alarm system without any sensor. Because the sensor is basic part of burglar alarm systems. I can publish new guides about this type questions.

  3. Mr. shankar khot, 8. November 2012, 14:55

    Can you tell me how burgler alarm and smoke detector works?with its IS Symbols.

  4. ritu sood, 5. January 2014, 8:14

    can you pls tell the construction, working,principle, etc. for making of burglar alarm using 555ic. need to make report on it urgently.

  5. Vinothkumar.V, 2. August 2014, 8:58

    i need all kind of burglar alarm’s circuit diagram and working principle


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