Position sensing and control means

Claim 1

A CONTROL SYSTEM FOR PROVIDING AT A PRIMARY STATION A CONTROL SIGNAL CORRESPONDING IN MAGNITUDE TO THE AMOUNT OF DISPLACEMENT AND IN SIGN TO THE DIRECTION OF DISPLACEMENT OF A CONTROLLED MOVING OBJECT WITH RESPECT TO A SUBSIDIARY REFERENCE STATION REMOTE TO SAID PRIMARY STATION, SAID CONTROL SYSTEM COMPRISING MEANS FOR PERIODICALLY TRANSMITTING AN OUTGOING ULTRASONIC WAVE TRAIN TOWARD SAID SUBSIDARY REFERENCE STATION AND SAID OBJECT, SIGNAL RETURN MEANS AT SAID SUBSIDIARY REFERENCE STATION AND AT SAID OBJECT AND RESPONSIVE TO RECEPTION OF EACH SAID TRANSMITTED ULTRASONIC WAVE TRAIN FOR TRANSMITTING A RETURNING ULTRASONIC WAVE TRAIN TOWARD SAID PRIMARY STATION, AT LEAST ONE OF SAID SIGNAL RETURN MEANS INCLUDING MEANS FOR GIVING A DISTANCE-INDEPENDENT SIGNAL CHARACTERISTIC TO EACH SAID WAVE TRAIN RETURNED THEREFROM TO RENDER SAID EACH SAID WAVE TRAIN DISCRIMINATABLE BY SAID CHARACTERISTIC, AND NOT MERELY BY DIRECTION OR TIME OF RECEPTION, FROM A WAVE TRAIN RETURNED FROM THE OTHER OF SAID SIGNAL RETURN MEANS, AND LOGIC MEANS AT SAID PRIMARY STATION FOR UTILIZING SAID DISCRIMINATABILITY TO INDICATE IN THE FORM OF A CONTROL SIGNAL THE SIGN AS WELL AS THE MAGNITUDE OF THE TIME INTERVAL BETWEEN THE ARRIVAL OF DIFFERNET RETURNING ULTRASONIC WAVE TRAINS RESULTING FROM THE SAME OUTGOING ULTRASONIC WAVE TRAIN.