How they work: With the transducer mounted at a fixed position, the extensible wire rope is attached to a moveable object. As movement occurs, the extension of the wire rope rotates an internal capstan and sensing device to produce an electrical output signal proportional to the wire rope extension and/or velocity. An internal torsion spring maintains tension on the wire rope and serves as the retraction mechanism. The sensing device may be a precision potentiometer, digital encoder or, for velocity measurement, a tachometer.