A circuit breaker includes an operating mechanism having powerful mechanism springs to achieve the requisite contact pressures for high current carrying capacity. A single crank of a rotary handle through a relatively small arc of 120.degree. resets the operating mechanism via a reciprocating slide and a latching mechanism, while loading the mechanism springs. Return of the handle to its original position shifts the line of action of the springs such as to abruptly straighten a toggle and achieve rapid closure of the circuit breaker contacts. The latching mechanism is equipped with plural circuit breaker tripping capabilities, together with a lockout and bell alarm switch accessory.