A secondary battery provided with a safety element comprising a conductive current interrupter and an insulation holder at thereof bottom. When the image detecting unit moves on the base via the frame, the post is in the first position and has no contact with the image detecting unit. Thus these poor electrical properties of the conventional semiconductor device with a shallow junction depth resulting from the shrink of design rules can be solved. The cover presses a front surface of the cartridge toward the rear surface, and presses a second side surface of the cartridge toward the first side surface.