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Magnetic system for discriminating between vehicles and personnel based upon their characteristic frequency signatures

  • US 3,889,181 A
  • Filed: 03/08/1974
  • Issued: 06/10/1975
  • Est. Priority Date: 03/08/1974
  • Status: Expired due to Term
First Claim
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1. A moving object detector and discriminating system which indicates the presence of vehicles and persons and differentiates therebetween comprising:

  • a first channel means for indicating the presence of a moving vehicle including first bandpass filter input means adapted to pass an input signal having a frequency within a first selected frequency range;

    a first level detector electrically connected to said first bandpass filter input means, said first level detector having a selected threshold level and adapted to block signals of lesser amplitude and to pass signals having an amplitude at said threshold level and above;

    a moving vehicle presence indicator; and

    first channel interconnection means adapted to interconnect the output of said first level detector to said moving vehicle presence indicator to activate same;

    a second channel means for indicating the presence of a moving person including second bandpass filter input means adapted to pass an input signal having a frequency within a second selected frequency range;

    a second level detector electrically connected to said second bandpass filter input means, said second level detector having a selected threshold level and adapted to block signals of lesser amplitude and to pass signals at said threshold level and above;

    a moving person presence indicator and second channel interconnection means adapted to interconnect the output of said second level detector to said moving person presence indicator to activate same;

    means for simultaneously applying an input signal, having frequency characteristics representative of the presence of moving objects of the vehicle and person variety, to said first and second channel means; and

    channel interrupter means adapted to block passage of the output signal of said second level detector to said moving person presence indicator, said channel interrupter means being responsive to the simultaneous occurence of output signals from said first and second level detectors.

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