Abstract: An electronic circuit breaker for use in A.C. power circuits is provided with means for varying the overload current response level at which the circuit breaker removes power from the load. The load current is conducted through a primary winding of a transformer, and a circuit breaker switch is responsive to voltage across the secondary winding of the transformer exceeding a predetermined magnitude corresponding to the selected overload current level to remove power from the load. A lockout circuit prevents reapplication of power other than by a manual reset switch. The overload current response level corresponding to the predetermined magnitude of the voltage across the secondary winding is variably selected by varying the inductive coupling between the primary winding and the secondary winding. The primary winding is wound about one leg of a magnetic core and the secondary winding is wound about another leg of the magnetic core.