Patent ID: 7292418

Claim:
A circuit for interrupting power to an appliance, comprising: a current detector providing an imbalance signal when current through first and second power supply lines is unbalanced by more than a predetermined amount; an interruption switch for interrupting current flow through at least one of the first and second supply lines; a ground fault detection sub-circuit configured to open the interruption switch upon receipt of the imbalance signal; a fault-inducing switch connecting the first and second supply lines and causing a current imbalance between the first and second supply lines when closed; an over-voltage detection sub-circuit configured to receive a signal indicative of voltage supplied to the appliance, and further configured to close the fault-inducing switch when the supplied voltage exceeds a voltage threshold V TRIP ; at least one TEST switch, the closure of which causes the over-voltage detection sub-circuit to receive a signal indicative of a supplied voltage exceeding V TRIP ; and at least one externally visible light-emitting component, and wherein the over-voltage detection sub-circuit is further configured: to determine, upon closure of the TEST switch, whether a signal corresponding to a supplied voltage exceeding V TRIP has been detected, to close the fault-inducing switch upon determining that a signal corresponding to a supplied voltage exceeding V TRIP has been detected, and to activate the at least one light-emitting component so as to indicate a malfunction upon determining that a signal corresponding to a supplied voltage exceeding V TRIP has not been detected.