Abstract: A face plate includes a passage for receiving a button cell. Disposed on the back of the face plate is a mounting plate. Between the mounting plate and the face plate, the edge of a diaphragm is gripped, the center part of which bulges resiliently outward. By means of pressure on the center part of the diaphragm, a circuit is closed. A cover having a center opening is hinged to the face plate. Through the opening there extends a pushbutton which is rotatable within limits relative to the cover and axially displaceable. Resting against the inside of the pushbutton is an annular contact element which is rotatingly integral therewith and has a contact tongue connected via a crosspiece. By rotating the pushbutton, the contact tongue can be brought into contact with a contact member disposed in a groove in the cover for turning on the hearing aid.