Airborne distance measuring equipment

Claim 1

IN AN INTERROGATOR-TRANSPONDER-RESPONSER SYSTEM FOR AIRBORNE AIRCRAFT IN WHICH PAIRS OF SHAPED PRECISELY-SPACED HIGH-FREQUENCY PULSE SIGNALS ARE TRANSMITTED AT RANDOM INTERVALS BY GROUND STATION TRANSPONDERS AT LEAST SOME OF WHICH SIGNALS ARE ORDINARILY AT LEAST IN RESPONSE TO INTERROGATION SIGNALS FROM INTERROGATING AIRCRAFT, THE METHOD OF PRODUCING PAIRS OF SIMILARLY SHAPED INTERROGATION SIGNALS ABOARD THE AIRCRAFT, SAID METHOD COMPRISING THE STEPS OF RECEIVING ABOARD THE PARTICULAR AIRCRAFT FROM A SELECTED GROUND STATION TRANSPONDER RANDOMLY-SPACED PAIRS OF SHAPED HIGH FREQUENCY PULSE SIGNALS NONE OF WHICH ARE NECESSARILY IN RESPONSE TO INTERROGATION SIGNALS PREVIOUSLY TRANSMITTED FROM SAID PARTICULAR AIRCRAFT, CONVERTING SID RECEIVED PULSE SIGNALS INTO PAIRS OF SIMILARLY SHAPED PULSE SIGNALS OF A DIFFERENT HIGH FREQUENCY, AND SELECTING CERTAIN OF SAID PAIRS OF CONVERTED SIGNALS FOR TRNSMISSION OF SAID SELECTED TRANSPONDER AS INTERROGATION SIGNALS.