A faulted circuit detector (12,22) has an electrically isolated and remotely positioned indicator (14) which indicates fault currents in a monitored conductor (18). When a fault of a predetermined magnitude is detected, a light pulse is transmitted from the detector (12,22) to the indicator via a fibre optic cable (16) where, upon receipt, the pulse is converted to an electrical pulse causing the indicator to indicate a "fault" state. A reset circuit (56) within the indicator resets the indicator at regular intervals to the "normal" state as long as a predetermined minimum voltage is present on the monitored conductor. A test circuit (34,48,50) is also provided to allow service personnel to field test the device with the monitored conductor in an energized state.