Alarm sensor

From DictionGloss

In communications systems, any device that can sense an abnormal condition within the system and provide a signal indicating the presence or nature of the abnormality to either a local or remote alarm indicator, and may detect events ranging from a simple contact opening or closure to a time-phased automatic shutdown and restart cycle. In a physical security system, an approved device used to indicate a change in the physical environment of a facility or a part thereof.