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Vehicle detection system and method of operation

  • US 3,895,344 A
  • Filed: 02/12/1970
  • Issued: 07/15/1975
  • Est. Priority Date: 02/12/1970
  • Status: Expired due to Term
First Claim
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1. A method of detecting a land vehicle which comprises:

  • detecting the acoustic emanations from the vehicle, selecting a higher energy band from the acoustic spectrum of the said emanations, tracking a given spectral line of said selected band, mixing the first signal provided by the selected line with a second signal of substantially the same frequency to provide a zero beat third signal, varying the frequency of said second signal in conformity with variations in the voltage of said third signal, removing high frequency and direct current components from said third signal to form a fourth signal, developing an output signal at a predetermined frequency and amplitude of said fourth signal, measuring the signal-to-noise ratio in at least Said selected band, and adjusting the level of at least the amplitude of said fourth signal at which an output signal will be developed in conformity with said ratio.

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