Pulsed ultrasonic detector

Claim 1

IN A SYSTEM FOR DETECTING VEHICLES AS THEY PASS THROUGH A DETECTION ZONE DEFINED BY A BEAM OF REPETITIVE SOUND PULSES, THE COMBINATION COMPRISING, TRANSMITTING MEANS FOR TRANSMITTING SAID BEAM OF SOUND PULSES, RECEIVING MEANS FOR RECEIVING SAID PULSES UPON THEIR BEING REFLECTED FROM SOUND REFLECTING SURFACES LYING WITHIN A GIVEN RANGE OF DISTANCES FROM SAID TRANSMITTING MEANS, SAID RECEIVING MEANS INCLUDING AN AMPLIFIER FOR AMPLIFYING SAID REFLECTION PULSES, GATING MEANS FOR CONTROLLING SAID AMPLIFIER TO BE RESPONSIVE ONLY THROUGHOUT A LIMITED TIME INTERVAL OCCURRING FOR A PREDETERMINED TIME AFTER THE TRANSMISSION OF EACH SOUND PULSE, OUTPUT CIRCUIT MEANS CONNECTED TO THE OUTPUT OF SAID AMPLIFIER AND BEING CONTROLLED THEREBY TO A DISTINCTIVE CONDITION TO INDICATE THE PRESENCE OF A VEHICLE WITHIN SAID DETECTION ZONE, SAID GATING CIRCUIT MEANS INCLUDING A DELAY LINE BEING ENERGIZED AT ONE END THEREOF BY SAID TRANSMITTING MEANS AT THE TIME OF TRANSMISSION OF EACH SOUND PULSE, SAID DELAY LINE HAVING A PLURALITY OF OUTPUT TAPS CLOSELY SPACED AND CONNECTED IN PARALLEL, SAID TAPS BEING SO POSITIONED ALONG SAID DELAY LINE THAT THEIR COMMON OUTPUT COMPRISES A GATING SIGNAL WHICH ENCOMPASSES THE EXPECTED RECEPTION TIME OF REFLECTION PULSES FROM REFLECTING SURFACES WITHIN SAID GIVEN RANGE OF DISTANCES, SAID SIGNAL ACTING UPON SAID AMPLIFIER AND CONTROLLING IT TO BE RESPONSIVE.