U.S. patent application Ser. Nos. 16/413,274 and 16/413,307, both of which are incorporated herein in their entirety, relate to isolating short circuit faults in a fire detection system. The '274 application describes an isolation switch that isolates a fault based on the inferred impedance on the system line in response to detecting a short circuit. The '307 application describes a similar switch that further includes determining a delay time before isolating the circuit, based on the measured voltage of the system line, recognizing that an isolator closest to the short will show a lower voltage than another isolator further from the short will, thus allowing the closer isolator to isolate the circuit so that there is no need for the further isolator to do so.

Referring to FIG. 1, a fire detection and alarm system 100 for a building 10 is disclosed. The building 10 may include two or more areas (e.g., rooms or floors) on separate detection and alarm zones 12a, 12b. The detection and alarm system 100 may include a fire detection and alarm panel 110 communicatively coupled with one or more devices 120 and configured to receive information from the devices 120. Examples of the devices 120 may include but are not limited to initiating devices such as pull stations, smoke detectors, heat detectors, carbon monoxide detectors or other types of devices for detecting hazardous conditions; and notification appliances such as strobes, horns, speakers, electronic reader boards and the like, as well as separate isolator units.