PURPOSE: To make it possible to independently and preferentially perform interruption operation, by performing interruption operation so as to be separated from and independent of the set content of a setting element and, moreover, detaching an opening and closing lever from the setting lever during interruption operation of "OFF".

CONSTITUTION: A manual lever 10 is operated to allow the protruded parts 10- A, 10-B, 10-C, which are provided on the outer periphery of said lever 10, to press the other ends of an intermediate lever 6 and an opening and closing lever 4 and the interruption operation of a switch 9 is performed manually. When the manual lever 10 is manually revolved in the direction shown by the arrow B to perform the interruption operation of "OFF", the protruded parts 10-A, 10-C are revolved from the position of the one-dot broken line to that of the solid line in the direction shown by the arrow B and the protruded part 10A pushes up the other end of the intermediate lever 6 to separate the adjusting screw 8 provided to the other end of said lever 6 from a plunger 9-A while the protruded part 10- C presses the other end of the opening and closing lever 4 and one end of this opening and closing lever 4 is revolved to the direction shown by the arrow A to be separated from a setting element 2.