Patent ID: 6021364
Filing Date: 2000-02-01
Classification: G08G

Abstract:
An apparatus for detecting the presence of a motor vehicle (105) in a detection zone (107), said apparatus comprising:a first electro-acoustic transducer (201) for receiving a first acoustic signal radiated from said motor vehicle and for converting said first acoustic signal into a first electric signal that represents said first acoustic signal;a second electro-acoustic transducer (203) for receiving a second acoustic signal radiated from said motor vehicle and for converting said second acoustic signal into a second electric signal that represents said second acoustic signal;spatial discrimination circuitry (305) for creating a third electric signal, based on said first electric signal and said second electric signal, that substantially represents the acoustic energy emanating from said detection zone;frequency discrimination circuitry (317) for creating a fourth signal based on said third signal; andinterface circuitry (119) for creating an output signal based on said fourth signal such that said output signal is asserted when said motor vehicle (105) is within detection zone (107) and whereby said output signal is retracted when said motor vehicle (105) is not within said detection zone (107).