To enable to always detect the position of an operating member during the opening/closing state of a cover member while employing a conventional opening/closing mechanism for a cover member.

A battery cover 39 which can be opened or closed to holes of a front cover 1 can move parallel to the outside plane of the cover 1 in a first direction. A sliding button 40 is provided on the cover 39 and can be moved in a second direction parallel to the first direction. The button 40 confines the movement of the cover 39 toward the first direction at a position of moving to the direction opposite to the second direction by being energized in the direction opposite to the second direction. When the button 40 is moved in the second direction against the energization to be released from the confinement and the cover 39 is moved to the first direction, the cover can rotate freely. When the button 40 exists at a position where it is moved in the second direction against the energization, a detecting switch 44 outputs a specified signal.