A circuit and device protects connected equipment from a broad range of unsafe conditions of over-voltage and under-voltage by disconnecting the line voltage before surge protection components, generally MOVs, are damaged from sustained surges. However, nuisance tripping of the protective circuit is avoiding by discriminating surges that are properly handled by the MOVs and components in the load or protective device. Further, the devise are protected from sustained high voltage line conditions, which would ordinarily result in repeated cycling between the on and off states as the line voltages fluctuates slightly at or about the trip threshold, as the circuit has a deliberate hysteresis such that the turn on voltage is about 10 to 20 V lower than the shut off threshold.