Methods of and apparatus for measuring distances

Claim 1

INTERROGATOR APPARATUS FOR USE IN CONJUNCTION WITH A RESPONDER IN A SYSTEM EMPLOYED FOR MEASURING DISTANCS, SAID APPARATUS COMPRISING MEANS FOR GENERATING A PULSE, MEANS FOR EXPANDING SAID PULSE IN ORDER TO PRODUCE AN EXPAND PULSE HAVING A CHARACTERISTIC WHICH VARIES ACCORDING TO A PREDETERMINED NON-REPETITIVE PATTERN, MEANS FOR TRANSMITTING FIRST SIGNAL DERIVED AT LEAST IN PART FROM SAID EXPANDED PULSE FOR RECEPTION BY THE RESPONDER TO CAUSE THE LATTER TO TRANSMIT A RETURN SIGNAL HAVING A CHARACTERISTIC PATTERN RELATED TO THAT OF SAID FIRST SIGNAL, MEANS FOR COMPRESSING SAID RETURN SIGNAL AS RECEIVED BY SAID INTERROGATOR SAID COMPRESSING MEANS INCLUDING MEANS FOR CROSS CORRELATING SAID RETURN SIGNAL WITH A PATERN REPRESENTING AT LEAST A PORTION OF THE EXPANDED PULSE AND COMPRISING A MAGNETOSTRICTIVE MEMBER, INPUT TRANSDUCER MEANS RESPONSIVE TO SAID RETURN SIGNAL AND COUPLED TO SAID MEMBER TO PRODUCE STRAINS THEREIN, AND MEANS INCLUDING OUTPUT TRANDUCER MEANS COUPLED TO SAID MEMBER FOR DEVELOPING A COMPRESSED RETURN SIGNAL, AT LEAST ONE OF SAID TRANSUCER MEANS BEING ADJUSTABLE ALONG SAID MEMBER TO COMPENSATE FOR PHASE SHIFTS, AND MEANS RESPONSIVE TO THE TIME INTERVAL BETWEEN SAID PULSE AND THE RESULTING COMPRESSED RETURN SIGNAL FOR MEASURING THE DISTANCE BETWEEN SAID INTERROGATOR AND SAID RESPONDER.