Security alarm systems are linked devices that are meant to detect intrusion. In their basic configuration, they are composed of a control box, an alerting system, an array of sensors or detectors, and a means of connecting the different components such that they can communicate with the control box.
They are used to protect residential, commercial, and industrial properties from burglaries and other criminal acts.
Alarm system components
The control box is the brain and it is also the direct link between the human occupants of a building and the electrical devices that make up the security alarm system.
Through the control box, various system configurations or instructions—such as the temporary deactivation of the alarm—may be set by the building occupants.
The alerting system is composed of sirens or flashing lights that are intended to warn building occupants and other people within the vicinity about a security breach. The alerting system is also designed to deter intruders and burglars from persisting to linger or enter the premises by increasing the likelihood of them getting caught and penalized for a criminal act.
Alarm systems are either connected by cables or communicate with each other using radio frequency (wireless).
The sensors and detectors are the systems’ eyes and ears that detect intruders. Sensors that are connected wirelessly have their own power supply or batteries.
Detecting security breaches
Through the use of different technologies, alarm system sensors are able to detect burglars and other types of intruders. These technologies include infrared motion detection, microwaves, ultrasound, microphones, vibration detection, and electromagnetic field sensors. Detectors may also include closed-circuit televisions that are intended to record the activities of intruders.
Infrared detectors are among the most commonly used for in security systems. Infrared detectors “sense” the presence of intruders by monitoring changes in the ambient temperature of a given area. Any organic creature that enters the area will cause a fluctuation in the ambient temperature, which–based on preset values—may cause the system to trigger an alarm.
Sound detectors usually use ultrasonic technology to detect an unauthorized presence in a given area. Like infrared detectors, ultrasonic detectors trigger the alarm when there are fluctuations in the sound waves in the area. Based on the principles of the Doppler Effect, fluctuations in the sound waves may be construed by the system as indicative of the presence of an intruder.
Microwave technology also uses the Doppler Effect but instead of ultrasonic vibrations, microwave sensors monitor a given area by emitting microwaves and sensing whether the reflected waves are more or less equal in intensity to the radiated waves. Any reduction in the wave properties could mean the presence of an intruder.
Broken glass detectors are designed to report whether a window or glass panel was broken by an intruder for the purpose of entering the building interior. Most glass detectors use vibrations created in the act of breaking the glass to determine whether a security breach has occurred.
In addition to these sensors, their security alarm systems also used devices that detect fire, heat, smoke, and carbon monoxide.