Ultrasonic distance scaling apparatus

Claim 1

DISTANCE SCALING APPARATUS INCLUDING IN COMBINATION A LENGTH OF MATERIAL, MEANS ADAPTED TO BE ENERGIZED TO VIBRATE SAID LENGTH AT A FIRST POINT, A PLURALITY OF SOURCES OF REFERENCE SIGNALS HAVING RESPECTIVE FREQUENCIES RELATED BY PREDETERMINED FACTORS, MEANS RESPONSIVE TO SAID SOURCES FOR ENERGIZING SAID VIBRATING MEANS TO PRODUCE VIBRATION PROPAGATED ALONG SAID LENGTH AT THE SPEED OF SOUND IN SAID MATERIAL, A PICK OFF DEVICE POSITIONED ALONG SAID LENGTH AT A SECOND POINT AND ADAPTED TO PRODUCE A SIGNAL IN RESPONSE TO SAID VIBRATION, MEANS FOR RESOLVING SAID PICK-OFF SIGNAL INTO COMPONENT SIGNALS CORRESPONDING TO SAID RESPECTIVE FREQUENCIES, MEANS FOR SHIFTING THE PHASE OF SAID REFERENCE SIGNALS, MEANS FOR COMPARING SAID COMPONENT SIGNALS WITH THE REFERENCE SIGNALS OF CORRESPONDING FREQUENCIES SHIFTED IN PHASE TO PRODUCE ERROR SIGNALS PROPORTIONAL TO THE PHASE DIFFERENCE BETWEEN THE COMPONENT SIGNALS AND THE RESPECTIVE REFERENCE SIGNALS OF CORRESPONDING FREQUENCIES SHIFTED IN PHASE AND MEANS