Appts. for sensing adjustment of variable impedance device

摘要

The variable impedance device has an integral switch. As the variable impedance device is adjusted, a wiper alternately operates the switch between open and closed states. This is detected to indicate when the device is being adjusted. The device comprises an elongated resistive element and an elongated switching element mounted co-extensively and parallel to each other. A conductive sliding wiper is operable to electrically connect both elements at any point along their respective lengths to corresp. elongated conductive elements. The switching-element comprises a series of conductive areas that are electrically connected together and separated by an alternating series of non-conductive areas. A variable impedance device with an end-of-travel return mechanism includes a movable actuator rigidly attached to the wiper and constrained to move between two endpoints. A spring engages the actuator near each end point such that when there are no other forces acting on the actuator the spring pushes the actuator back a predetermined distance from each end point. As the actuator traverses this distance, the integral switch pref. undergoes at least one state change.