Distance measuring circuit

Claim 1

APPARATUS FOR DETERMINING THE TIME RELATIONSHIP BETWEEN FIRST AND SECOND REPETITIVE ELECTRICAL SIGNALS EACH HAVING A FIRST REPETITION FREQUENCY COMPRISING MEANS FOR GENERATING A FIRST OSCILLATORY ELECTRICAL SIGNAL AT A FREQUENCY OF OSCILLATION SUBSTANTIALLY HIGHER THAN SAID FIRST REPETITION FREQUENCY, MEANS FOR GENERATING A THIRD REPETITIVE ELECTRICAL SIGNAL AT A SECOND REPETITION FREQUENCY LOWER THAN SAID FIRST REPETITION FREQUENCY, MEANS FOR GENERATING A SECOND OSCILLATORY ELECTRICAL SIGNAL HAVING A FREQUENCY RELATED TO SAID SECOND REPETITION FREQUENCY BY THE SAME FACTOR WHICH RELATES THE FREQUENCY OF SAID FIRST OSCILLATORY SIGNAL TO SAID FIRST REPETITION FREQUENCY, MEANS FOR HETERODYNING SAID FIRST AND SECOND OSCILLATORY SIGNALS TO DERIVE A SIGNAL AT A FREQUENCY EQUAL TO THE DIFFERENCE BETWEEN THE FREQUENCIES OF SAID FIRST AND SECOND OSCILLATORY SIGNALS, MEANS COUPLED TO SAID HETERODYNING MEANS FOR COUNTING CYCLES OF SAID DIFFERENCE FREQUENCY SIGNAL, MEANS COUPLED TO RECEIVE SAID FIRST AND SAID THIRD REPETITIVE SIGNALS FOR PROVIDING A SIGNAL TO START SAID COUNTING MEANS EACH TIME SAID FIRST AND THIRD REPETITIVE SIGNALS ARE IN COINCIDENCE, AND MEANS COUPLED TO RECEIVE SAID SECOND AND SAID THIRD REPETITIVE SIGNALS FOR PROVIDING A SIGNAL TO STOP THE CYCLE COUNTING IN SAID COUNTING MEANS EACH TIME SAID SECOND AND SAID THIRD REPETITIVE SIGNALS ARE IN COINCIDENCE.