Security alarm

[GROUP 1: Components]
– Alarm control panel (ACP) or panel: Reads sensor inputs, tracks arm/disarm status, and signals intrusions
– Sensors: Detect intrusions at the perimeter or within the protected area
– Alerting devices: Indicate an alarm condition through bells, sirens, or flashing lights
– Keypads: Function as the human-machine interface to the system
– Monitoring service: Contacts a central monitoring station in the event of an alarm

[GROUP 2: Sensor types]
– Hermetically sealed reed switches: Operate with an electrically conductive switch and a magnet, allowing detection of faults
– Passive infrared detectors (PIR): Detect abrupt changes in temperature caused by an intruder’s heat energy
– Infrasound detectors: Detect infrasound waves below 20 hertz, which are inaudible to humans
– Ultrasonic detectors: Transmit ultrasonic sound waves and detect frequency changes due to object motion
– Other sensor types: Include microwave detectors, vibration sensors, and photoelectric beams

[GROUP 3: Hermetically sealed reed switches]
– Common two-piece sensor with a switch and magnet
– Switch closes or opens based on magnetic field proximity
– Used in wired or wireless door/window contacts
– Allows alarm control panel to detect faults in zones or circuits
– Provides reliable detection and integration with the security system

[GROUP 4: Passive infrared detectors (PIR)]
– Commonly found in households and small businesses
– Detect temperature changes caused by an intruder’s movement
– Trigger detection by quick temperature rise and fall
– Available in various fields of view for wall or ceiling mounting
– Require a power supply in addition to the detection circuit

[GROUP 5: Infrasound detectors]
– Detect sound waves below 20 hertz, inaudible to humans
– Can detect potential intruders testing doors or applying pressure
– Consist of a speaker, order-frequency filter, A/D converter, and microcomputer
– Used to detect burglars before they enter a house
– Sensitivity depends on home size and presence of animalsSources: