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Coin discriminator for electronic parking meter

  • US 4,895,238 A
  • Filed: 03/25/1988
  • Issued: 01/23/1990
  • Est. Priority Date: 04/16/1987
  • Status: Expired due to Fees
First Claim
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1. A coin discriminator system for use in an electronic parking meter comprising:

  • means for accepting a deposited coin in said electronic parking meter;

    a single inductor;

    means for guiding said deposited coin past said inductor, said deposited coin causing a momentary change in the value of inductance of said inductor;

    phase lock loop electronic circuit having an input connected to said inductor, said phase lock loop electronic circuit providing a correction signal for said phase lock loop electronic circuit, said correction signal compensating for said change in the value of inductance of said inductor, said correction signal having a wave shape unique to said deposited coin; and

    microprocessor receiving said correction signal waveform for comparison to a plurality of predetermined wave shapes of a plurality of known coins to thereby identify said deposited coin, said plurality of predetermined wave shapes stored in a memory connected to said microprocessor,said phase lock loop electronic circuit having an L-C oscillator providing a predetermined input frequency and outputting a series of pulses when a deposited coin passes said inductor; and

    an integrating circuit for integrating said series of pulses and outputting said correction signal.

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