Alarm Systems and Sensors

For this Web site, “alarms” and “alarm systems” refer to systems selected, designed, installed, and used primarily for intrusion detection and duress protection. An electronic security system may contain other warning functions (fire, medical emergency, temperature variation, water level, and so forth), but those functions are beyond the scope of this Web site.

Sensors are designed to respond to one or more changes in some condition. In most alarm systems, the output of the sensors is the equivalent of opening or closing a switch. Sensors must have a high probability of detection (PD) for the type of intrusion they are designed for and have a low rate of unwanted alarms for all expected environmental and site conditions. Some sensors are specially designed to be used outdoors, primarily for perimeter protection. Other sensors are designed to be used indoors for protection of the interior perimeter and enclosed areas (volumetric protection). This Web site briefly discusses different sensors.