Abstract: The invention is concerned with a motion picture projector or camera, with a claw for feeding the motion picture film, having at least one switch provided in one or several electric circuits of the motion picture projector or camera, which switch is controlled by said claw. An 8-mm motion picture camera in which a switch for various circuits of the camera is provided within the intercept of the claw is already familiar. In such an arrangement, contact elements of the switch are kept mutually in mesh by the claw while it engages the film or disengages from its perforations and if there is no film, the claw releases or opens these contact elements. Switching contacts of this type may be provided, e.g., in the electric circuits of the feed mechanisms or of the exposure control device of a motion picture camera. In this way, when no film is inserted, the batteries are unable to discharge.

Abstract: A phototransistor is coupled to a relay coil and the base of a switching transistor. Light impinging on the phototransistor will cause it to conduct, switching on the transistor causing current flow in the relay coil. Fluctuating light intensity on the phototransistor will cause a corresponding fluctuation of current in the relay coil. A predetermined level of current in the coil will maintain the relay closed.