Abstract: An electronic module for ground fault circuit interrupters (GFCI) in both circuit breaker and receptacle configurations includes a signal processor having a plurality of fault signal threshold stages for differentially charging an integrating capacitor in accordance with the magnitude of the fault signal as amplified by a high gain differential amplifier. The accumulated charge on the integrating capacitor controls the generation of a trip signal. The processor also includes a highly stable grounded neutral excitation oscillator and a noise rejection network to combat nuisance tripping.