An isolation circuit according to an embodiment of the present invention includes an isolation switch and a controller. The isolation switch may be coupled with a network system line (for example, in a fire detection system, a signaling line circuit, an initiating device circuit or a notification appliance circuit) at a first side of the system line and at a second side of the system line. The controller, upon detection of a short circuit on the system line, may receive a current level signal that is based on (or derived from) electrical current on the system line and a voltage level signal that is based on (or derived from) a voltage on the system line. Based on at least one of these signals, i.e., based on the current and/or voltage levels on the system line, the controller may determine whether the current or voltage is excessive. If either current or voltage are determined to be excessive, e.g., by comparison with a predetermined threshold, the controller may isolate the first side from the second side by opening the isolation switch if it is not already open. If, on the other hand, neither the current nor the voltage are excessive, the controller may cause the isolation switch to close or to remain closed, thus un-isolating the first side from the second side so that they are in electrical communication with each other.

The isolation circuit may further include a current monitor coupled between the system line and the controller. The current monitor may sense the electrical current on the system line and generate the current level signal based on the sensed electrical current.