Abstract: A rocking beam is movable into an "on" and an "off" position by actuating means which actuate linkage means and work against the force of a spring urging the beam into an intermediate trip-position. Through a guide surface the beam actuates a toggle assembly composed of two toggle levers linked by a toggle joint and having distal joints linked with a contact actuating lever and a pawl lever, respectively. When the pawl lever is restrained by the ratchet, the movement of the toggle joint caused by moving the actuating means into the "on" or "off" position results only in the opening and closing of contacts through a movement of their actuating lever. A readiness for switching on can be obtained by resetting the actuating means from the trip-position into the "off" position.