Radar altimeters

Claim 1

A DISTANCE MEASURING DEVICE OPERABLE OVER A PREDETERMINED RANGE COMPRISING: SAWTOOTH GENERATING MEANS OPERABLE IN RESPONSE TO A FIRST SIGNAL; DOUBLE INTEGRATING MEANS, COMPARATOR MEANS CONNECTED TO RECEIVE SIGNALS FROM SAID SAWTOOTH GENERATING MEANS AND SAID DOUBLE INTEGRATING MEANS AND TO PRODUCE AN OUTPUT SIGNAL WHEN THE INSTANTANEOUS MAGNITUDE OF THE SAWTOOTH SIGNAL IS EQUAL TO THE OUTPUT OF SAID DOUBLE INTEGRATING MEANS; GATE GENERATING MEANS OPERABLE IN RESPONSE TO THE OUTPUT SIGNAL FROM SAID COMPARATOR MEANS FOR PRODUCING FIRST AND SECOND GATES HAVING A FIXED TIME RELATIONSHIP; SIGNAL GENERATING MEANS FOR GENERATING A SECOND SIGNAL SOME TIME AFTER TIME THE OCCURRENCE OF SAID FIRST SIGNAL; FIRST COINCIDENT GATE MEANS CONNECTED TO RECEIVE THE SECOND SIGNAL FROM SAID SIGNAL GENERATING MEANS; MEANS CONNECTING THE FIRST GATE FROM SAID GATE GENERATING MEANS TO SAID FIRST COINCIDENT GATE MEANS WHEREBY SAID FIRST COINCIDENT GATE MEANS PRODUCES AN OUTPUT SIGNAL PROPORTIONAL TO THE LEADING EDGE OF SAID SECOND SIGNAL; MEANS CONNECTING THE OUTPUT SIGNAL FROM SAID FIRST COINCIDENT GATE MEANS TO THE INPUT OF SAID DOUBLE INTEGRATING MEANS; SECOND COINCIDENT GATE MEANS CONNECTED TO RECEIVE THE SECOND SIGNAL FROM SAID SIGNAL GENERATING MEANS; MEANS CONNECTING THE SECOND GATE FROM SAID GATE GENERATING MEANS TO SAID SECOND COINCIDENT GATE MEANS WHEREBY SAID SECOND COINCIDENT GATE MEANS PRODUCES AN OUTPUT SIGNAL PROPORTIONAL TO THE MAGNITUDE OF SAID SECOND SIGNAL WHEN SAID SECOND GATE AND SAID SECOND SIGNAL ARE TIME COINCIDENT; MEANS CONNECTING THE OUTPUT SIGNAL OF SAID SECOND COINCIDENT GATE MEANS TO SAID SIGNAL GENERATING MEANS SO AS TO HOLD THE MAGNITUDE OF SAID SECOND SIGNAL CONSTANT; RANGE SWEEP MEANS HAVING AN INPUT AND AN OUTPUT; MEANS CONNECTING THE INPUT OF SAID RANGE SWEEP MEANS TO THE OUTPUT OF SAID SECOND COINCIDENT GATE MEANS, THE OUTPUT SIGNAL FROM SAID SECOND COINCIDENT GATE MEANS HOLDING SAID RANGE SWEEP MEANS INOPERATIVE; AND MEANS CONNECTING THE OUTPUT OF SAID RANGE SWEEP MEANS TO SAID DOUBLE INTEGRATING MEANS, WHEREBY SAID RANGE SWEEP MEANS, WHEN OPERATIVE, SWEEPS THE OUTPUT OF SAID DOUBLE INTEGRATING MEANS TO A LIMIT IN ONE DIRECTION, SAID RANGE SWEEP MEANS FURTHER HAVING MEANS OPERATIVE UPON SAID DOUBLE INTEGRATING MEANS REACHING SAID LIMIT IN ONE DIRECTION TO SWEEP THE OUTPUT OF SAID DOUBLE INTEGRATING MEANS TO A LIMIT IN AN OPPOSITE DIRECTION.