Method and apparatus for integrating manual input

  • US 6,323,846 B1
  • Filed: 01/25/1999
  • Issued: 11/27/2001
  • Est. Priority Date: 01/26/1998
  • Status: Expired due to Term
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First Claim
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1. A sensing device that is sensitive to changes in self-capacitance brought about by changes in proximity of a touch device to the sensing device, the sensing device comprising:

  • two electrical switching means connected together in series having a common node, an input node, and an output node;

    a dielectric-covered sensing electrode connected to the common node between the two switching means;

    a power supply providing an approximately constant voltage connected to the input node of the series-connected switching means;

    an integrating capacitor to accumulate charge transferred during multiple consecutive switching of the series connected switching means;

    another switching means connected in parallel across the integrating capacitor to deplete its residual charge; and

    a voltage-to-voltage translation device connected to the output node of the series-connected switching means which produces a voltage representative of the proximity of the touch device to the sensing device.

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