A symmetrical differential capacitive sensor includes a movable element pivotable about a geometrically centered rotational axis. The film feed mechanism has a transport grip having a transport grip clip and at least one transport grip tip which engages in a sprocket hole of a motion-picture film that is transported at a predefinable film transport speed by the kinematics of the transport grip. The instrument possesses two jaws that can be moved relative to one another for the purpose of generating a gripping force, at least one of the jaws having a wire-receiving device which positions a bent wire, which is to be received, in a plane substantially parallel to the direction of gripping force. The linear motion or alternatively oscillating motion of the movable assembly is converted by the motion conversion mechanism or alternatively by the retractable motion-conversion mechanism into a continuous circular motion for the rotatable rollers of the rolling foot-powered apparatus. The checksum is calculated each time the file is created andor modified. The circuit including: a delayed lock loop circuit for receiving a clock signal and generating a control signal for adjusting an internal delay of the clock signal; and means for generating a delayed clock signal in response to the control signal.