The Inside And Out Of a Home Alarm System

Control Panel Circuit Board

Open Look at a Security Touchpad


The times when the barking dogs were the indication of any intrusion have been gone for long. In the modern era, they have been replaced by the modern alarm systems which never sleep. So have you ever thought about the components that make an alarm system functional?

Alarm System Mechanism:

An alarm system contains sensors which detect the changes in the surroundings. If and when any specific change is detected by the sensors a series of events is set into motion depending on the alarm type and function, which may or may not include the Siren’s voice operation being set to its ON state thus calling the police station etc.

The circuit of the alarm system is based on very common and easily available electrical components which change their state whenever a certain event called INTERRUPT happens. The alarm circuits can be of two types

  • Closed circuit system
  • Open circuit system

Closed circuit system:

In this type of alarm systems, whenever we close the door the alarm circuit is closed and thus it sets its routine into motion like sounding the buzzer and calling the specific authorities.

Open circuit system:

In this type of alarm system, the current begins to flow whenever a door is opened and thus the alarm starts its routine. In both the cases, the alarm is triggered by the current flow which further depends upon the door position.

Basic Door Alarm Circuitry:

blue print of alarm system grid

The most basic alarm system consists of a switch which, whenever it is closed or opened; sets on the siren and performs its routine depending on its programming. The modern alarm systems uses sensors like heat sensors, light sensors, and infrared sensors to trigger the alarm. The alarms can also be used for the protection of babies and can also be installed at the windows.

Following are the primary components of an Alarm system:

  • Master Control Panel:

The CPU resides inside it and it is responsible for controlling all the operations of an alarm system.

  • Keypad:Wireless Security Keypad

The key pad provides the users access to the alarm system so as to arm and disarm it. The functionality of the alarm system depends upon the commands given through the key pad.

  • Sensors:

Many sensors are available that are used in door alarm systems a few of which are listed below:

Door and Window sensors: Door & Window Sensor

Here is what you didn’t know about these standard devices… These sensors form the basic infrastructure of the alarm system and they are installed at every place which can be the entry point of the intruder. Whenever a change is incurred an INTERRUPT signal is sent to the Master Control Panel which in turn switches ON the alarm.

Passive infrared motion sensors (PIRs):

These sensors detect the heat and one sensor installed in the room is enough to trigger the alarm. Since this alarm is very sensitive and has a very large range thus special precautions must be taken to decide the location of its installation. It must be kept away from heat generating objects otherwise a false alarm may be triggered.


This may all be Geek language but it is interesting to take a deeper look at how the basic alarm system works.  From the signals it sends from your home to monitoring and then relaying onto the local police it is a complicated process.  Luckily as alarm systems evolve the ease of use does as well with automation gadgets added and wireless functions getting better. 

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