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Article detection system and method

  • US 3,964,041 A
  • Filed: 07/01/1974
  • Issued: 06/15/1976
  • Est. Priority Date: 07/01/1974
  • Status: Expired due to Term
First Claim
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1. An article sensing and detection system comprising:

  • first transducer means for generating a sensing signal adapted to impinge on an article to be sensed;

    frequency sensitive circuit means generating a continuous fixed frequency modulating signal, said frequency sensitive circuit means being responsive to a signal of said fixed frequency at its input for generating a first output and being responsive to the absence of a signal of said fixed frequency at its input for generating a second output;

    first circuit means for applying said fixed frequency modulating signal to said first transducer means to effect oscillation of said sensing signal at said fixed frequency;

    second transducer means for sensing said oscillating sensing signal, said second transducer means being responsive to said oscillating sensing signal impinging on an article to be sensed for generating a feedback signal respresentative thereof and oscillating at said frequency;

    second circuit means for coupling said oscillating representative feedback signal to the input of said frequency sensitive circuit means;

    said frequency sensitive circuit means being responsive to the presence a predetermined number of cycles of said oscillating representative feedback signal at its input for generating one of said first and second outputs indicative of the detection of said article.

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