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Multiple sheet detector apparatus and method

  • US 7,293,702 B2
  • Filed: 06/30/2005
  • Issued: 11/13/2007
  • Est. Priority Date: 07/01/2004
  • Status: Active Grant
First Claim
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1. An apparatus comprising:

  • a sound transmitter operative to transmit a sound wave through sheet media;

    a sound receiver operative to produce at least one receiver signal responsive to the sound wave after the sound wave has passed through sheet media;

    a filter circuit operative to filter the at least one receiver signal with respect to two reference signals which differ in phase by substantially 90 degrees; and

    at least one processor operative, responsive to at least one output from the filter circuit, to determine data representative of at least one change in phase of the sound wave caused by passage through sheet media;

    wherein the at least one processor is operative, responsive to the determined data, to determine whether sheet media through which the sound wave has passed comprises at least one of a single sheet and multiple sheets.

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