Abstract: A resettable ground fault circuit interrupter most advantageously suited for use with 400-Hz aircraft electrical systems and designed to interrupt the AC power between an aircraft electrical system and one or more electrical appliances being operated therein when a ground fault occurs. The circuit relies upon an imbalance sensor which is implemented in the preferred embodiment disclosed herein as a multi-turn coil of a transformer through which input wires connected to an AC input terminal are threaded so that an imbalance resulting from a ground fault can be detected by the coil. The signal generated by the coil as a result of such an imbalance is then amplified and applied to a thyristor, the conducting or non-conducting state of which determines whether or not the circuit is in a configuration for interrupting the AC signal or not interrupting the AC signal. Light emitting diodes are utilized to indicate the interruption status of the circuit.