A Security alarm is a system designed to detect intrusion.The sensor is connected to a control unit by means of low-voltage wiring or a narrow radio frequency signal which is used to interact with the response device. The most commonly used security sensors are to mark the opening of a door or window or to detect movement through a passive infrared sensor (PIR sensor). The installation of safety alarms in new buildings is generally applied in an imprint because it is more economical, while installations for repairs (retrofitting) often use wireless systems to make them faster to install.
Security alarms are used in residential, commercial, industrial, and military properties for protection against burglary (theft) or property damage, as well as personal protection against intruders. Security alarms in residential areas show a correlation with decreased theft.
Some alarm systems serve a single purpose of burglary protection; combination systems provide both fire and intrusion protection. Intrusion alarm systems may also be combined with closed-circuit television surveillance (CCTV) systems to automatically record the activities of intruders, and may interface to access control systems for electrically locked doors. Systems range from small, self-contained noisemakers, to complicated, multirally systems with computer monitoring and control. It may even include two-way voice which allows communication between the panel and Monitoring station.