A housing includes a case member having an opened front face, and a cover member firmly fixed with the case member to close the opened front face of the case member. The case member has a penetration hole penetrating its side face. A movable part includes an inner member disposed inside the housing to control a circuit, and an outer member being a discrete piece from the inner member and exposed outside the housing to be manipulated by a user. The outer member includes a shaft part inserted through the penetration hole.