A faulted circuit detector (10) having an electrically isolated and remotely positioned indicator (14) detects fault currents in a monitored conductor (18). When a fault of a predetermined magnitude is detected, a light pulse is transmitted from the detector to the indicator via a fiber 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. The detector includes a temperature compensation circuit (150) and low pass filter circuit (160) so as to prevent misoperation due to varying ambient temperatures or high frequency transients. A test circuit (48, 50, 34) is also provided to allow service personnel to field-test the device with the monitored conductor in an energized state.