Auxiliary systems typically receive fire alarm signals over their circuits. The circuits have to be monitored for integrity. Thus, trouble signals are received at the public receiving station, where there are trained, competent people on duty.

Trouble signals have to be distinct from alarm signals and indicated by both a visual and audibleThe audible signal can be common to all of the circuits monitored. signal. The audible can be silencedIf a second fault occurs on another circuit, the audible signal has to be re-sounded., but the visible signal has to stay until restoration is achieved.

NOTE: This is an unformatted excerpt from our online fire protection training library.