Addressable fire detection systems are normally designed as loops, with the connecting wires starting and finishing at the control panel. Detectors and interfaces are connected at intervals along these cables.
When short circuits occur on a loop, the consequences can be serious, in worst case making the affected loop entirely inoperative. The purpose of isolating circuits is to protect the loop in the event of a short circuit by disconnecting the part of the loop where the short circuit has occurred, thereby isolating the short circuit and only rendering a small part of the loop inoperative. The remainder of the loop continues to function normally. When the short circuit fault has been rectified, the isolating circuitry reconnects the affected section of the loop.
The more isolators that are installed on the loop, the smaller part of the loop is affected by a short circuit condition. By regulation there should never be more than 32 devices between isolators, but it is recommended that isolation is placed at least at every entry and exit point to a zone.