A system for isolating faults in emergency systems, the system comprising: first and second power lines (22, 24); a circuit controller; a first system line isolator connected between the first power line and the circuit controller and a second system line isolator connected between the second power line and the circuit controller; a plurality of zones (18a - 18n), each zone including first zone line isolators (14a - 14n) connected to the first power line, second zone line isolators (16a - 16n) connected to the second power line, and one or more emergency devices (20a - 20n) connected between respective pairs of a first zone line isolator (14a - 14n) and a second zone line isolator (16a - 16n), Wherein, during normal system operation, the first zone line isolators (14a - 14n) and the first and second system line isolators (26a - 26b) are closed and the second zone line isolators (16a - 16n) are open; Wherein the first system line isolator is adapted to detect a short circuit fault in any of the zones (18a - 18n) by sensing a spike in current and a drop in voltage and, subsequently to open, cutting off power from the circuit controller to the first power line, and wherein, in response to said loss of power on said first line, all first zone line isolators (14a - 14n) are adapted to open; Wherein, a short period of time after said opening of the first system line isolator, the circuit controller is adapted to close said first system line isolator, and wherein subsequently thereto, each first zone line isolator (14a-14n) is adapted to determine if there is a short circuit fault in the corresponding zone (18a - 18n) by applying a small current to the corresponding zone (18a -18n) and monitoring the response; said first zone line isolator (14a-14n) being further adapted to remain open if the respective zone (18a-18n) contains a short circuit fault and to close if no short circuit fault is present in said corresponding zone (18a-18n). first and second power lines (22, 24); a circuit controller; a first system line isolator connected between the first power line and the circuit controller and a second system line isolator connected between the second power line and the circuit controller; a plurality of zones (18a - 18n), each zone including first zone line isolators (14a - 14n) connected to the first power line, second zone line isolators (16a - 16n) connected to the second power line, and one or more emergency devices (20a - 20n) connected between respective pairs of a first zone line isolator (14a - 14n) and a second zone line isolator (16a - 16n), Wherein, during normal system operation, the first zone line isolators (14a - 14n) and the first and second system line isolators (26a - 26b) are closed and the second zone line isolators (16a - 16n) are open; Wherein the first system line isolator is adapted to detect a short circuit fault in any of the zones (18a - 18n) by sensing a spike in current and a drop in voltage and, subsequently to open, cutting off power from the circuit controller to the first power line, and wherein, in response to said loss of power on said first line, all first zone line isolators (14a - 14n) are adapted to open; Wherein, a short period of time after said opening of the first system line isolator, the circuit controller is adapted to close said first system line isolator, and wherein subsequently thereto, each first zone line isolator (14a-14n) is adapted to determine if there is a short circuit fault in the corresponding zone (18a - 18n) by applying a small current to the corresponding zone (18a -18n) and monitoring the response; said first zone line isolator (14a-14n) being further adapted to remain open if the respective zone (18a-18n) contains a short circuit fault and to close if no short circuit fault is present in said corresponding zone (18a-18n).