Abstract: A power supply control device is provided in a fire alarm system having terminals such as fire detectors and/or repeaters with comparators to detect abnormalities such as fire or an operating status of controlled apparatus, and is equipped with a reference voltage supply a source to supply reference voltage to the comparators, and a power supply control to allow the reference voltage to be supplied to the comparators only during the detecting time.

Abstract: A fire alarm system includes a receiver unit connected to a plurality of terminal unit groupings, each of the terminal unit groupings made up of a plurality of terminal units. The fire alarm system operates in one of a system polling mode, a point polling mode and a selecting mode. In the system polling mode, the receiver units polls all of the terminal units and provides a grouping response period in which each of the terminal unit groupings is permitted to respond to the receiver unit polling. If one of the terminal units of a particular grouping undergoes a status change, such a terminal unit transmits to the receiver unit a group response signal during the corresponding group response period. Then, the system enters the point polling mode, in which the terminal units of the terminal unit grouping corresponding to the group response period in which a group response signal was received are polled.