Vehicle location system

摘要

1,064,028. Ultrasonic distance-measuring. STANDARD TELEPHONES & CABLES Ltd. Nov. 13, 1964 [Nov. 16, 1963], No. 46296/64. Heading H4D. In an ultrasonic warning- system for indicating the proximity of one road vehicle to another each vehicle carries a radio receiver and at least one ultrasonic pulse-transmitter and receiver, and the ultrasonic pulse-transmitters in all vehicles are triggered substantially in synchronism by a radio pulse received from road-side radio transmitters, the distance between one vehicle and an adjacent vehicle being measured by measuring the time interval between the arrival, at the one vehicle, of the radio pulse and of the ultrasonic pulse from the adjacent vehicle. For detecting vehicles travelling in the same direction and either in front or behind, each vehicle carries a forwardly radiating ultrasonic transmitter 3a and rearwardly directed microphone 12 (constituting a first channel operating at, for example, 30 kc/s.), and a rearwardly radiating ultrasonic transmitter 4a and forwardly directed microphone 13 (constituting a second channel operating at, for example, 50 kc/s.). The time interval is measured in the two channels by electronic counters 5, 6 which are fed through gates 7, 8 with clock pulses from a generator 9. The leading edge of the demodulated radio pulse from the radio receiver, 1, sets the counters 5, 6 to zero and the trailing edge of the pulse then triggers the ultrasonic transmitters 3a, 4a and opens gates 7, 8 to start the counters 5, 6. The arrival of an ultrasonic pulse at microphone 12 or 13 closes the appropriate gate 7 or 8 to stop counter 5 or 6 respectively. The counters 5, 6 have visual read-outs 15, 14 indicating distance, each readout comprising a row of neon lamps which may be of different colours to indicate different distances. The measurement cycle is repeated at the pulse repetition frequency of the roadside radio transmitters (S) (Fig. 1, not shown), e.g. once every one to five seconds. In order to detect oncoming vehicles, a forwardlydirected microphone (not shown) may be switched into the 30 kc/s. channel in place of the rearwardly-directed microphone 12.