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Vehicle tracking system

  • US 5,218,367 A
  • Filed: 06/01/1992
  • Issued: 06/08/1993
  • Est. Priority Date: 06/01/1992
  • Status: Expired due to Fees
First Claim
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1. A vehicle tracking system, comprising:

  • an array of fixed cellular signal receiving and transmitting units each covering a predetermined area and forming part of a cellular telephone network, each fixed cellular unit including means for transmitting cellular voice and control channel signals identifying said unit;

    a signal processing unit for mounting in a vehicle, the unit including signal generating means for generating emergency signals on detection of an emergency condition, the signal generating means including means for continuously scanning all voice and control channel signals from any fixed cellular units within range of the vehicle during an emergency condition, means for determining the signal strengths of any received cellular voice and control signals, and means for transmitting an emergency signal from the vehicle for each set of received signals, each emergency signal including the received cellular control signals and determined signal strengths; and

    a central monitoring means for receiving said emergency signals and for computing an approximate vehicle location from said cellular control signals and signal strengths.

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