Ultrasonic vehicle detector

Claim 1

IN A SYSTEM FOR DETECTING THE PASSAGE OF AN OBJECT, SAID SYSTEM BEING OF THE TYPE WHEREIN A BEAM OF REPETITIVE ENERGY PULSES ARE PRODUCED BY TRANSMITTING MEANS AND AT LEAST A PORTION OF EACH PULSE IN THE ABSENCE OF SAID OBJECT ENERGIZES A RECEIVING TRANSDUCER A PREDETERMINED TIME AFTER ITS GENERATION BY SAID TRANSMITTING MEANS BUT WHEREIN SAID PULSES ARE BLOCKED FROM REACHING AND ENERGIZING SAID RECEIVING TRANSDUCER AT SAID PREDETERMINED TIME UPON THE PASSAGE OF SAID OBJECT, THAT IMPROVEMENT COMPRISING, AMPLIFIER MEANS FOR AMPLIFYING THE ELECTRICAL OUTPUT SIGNAL OF SAID RECEIVING TRANSDUCER, STORAGE MEANS, CIRCUIT MEANS FOR GENERATING A SIGNAL PROPORTIONAL TO THE AMPLITUDE OF THE OUTPUT OF SAID AMPLIFIER MEANS OCCURRING ONLY THROUGHOUT THE NORMAL TIME OF RECEPTION OF SAID PORTION OF SAID TRANSMITTED PULSE, CIRCUIT MEANS FOR APPLYING EACH SAID GENERATED SIGNAL TO SAID STORAGE MEANS, MEANS CONTROLLED BY SAID SIGNAL STORED IN SAID STORAGE MEANS FOR CONTROLLING THE GAIN OF SAID AMPLIFIER MEANS AND MEANS CONTROLLING SAID STORAGE MEANS TO RETAIN THE SIGNAL STORED THEREIN FOR AT LEAST AS LONG A TIME AS THE MAXIMUM TIME THAT SAID PULSES ARE EXPECTED TO BE BLOCKED BY A SLOW MOVING OBJECT.