Alarm System, Automatic

Alarm System, Automatic 

a system that converts information on the progress of a monitored process or the condition of a monitored system into a signal suitable for human perception. Generally light or sound signals are used—for example, the flashing of a lamp, the ringing of a bell, or the sounding of a siren. The conversion is carried out by an automatic signaling device, and the signal is presented for human perception by an indicating device. The signaling device compares current monitoring data continuously or periodically with limits specified in accordance with, for example, engineering requirements, safety precautions, fire-prevention regulations, and explosion-prevention requirements. When the monitored variable exceeds permissible limits, the signaling device is actuated.

A distinction is made between two-position and three-position signaling devices. A two-position device recognizes one limit, and a three-position device recognizes two limits, upper and lower. In three-position devices, the exceeding of the lower limit often constitutes a warning that hazardous or emergency conditions are being approached. To increase the reliability of alarm systems, duplicate signal circuits are often provided. Measures are also taken to eliminate the possibility of a false signal owing to a malfunction of a component of the signaling device.

A. V. KOCHEROV