In telecommunication, the term alarm sensor has the following meanings: 1. In communications systems, a 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 , and (b) may detect events ranging from a simple contact opening or closure to a time-phased automatic shutdown and restart cycle. 2. In a physical security system, an approved device used to indicate a change in the physical environment of a facility or a part thereof.