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Graphic tablet and method

  • US 4,492,819 A
  • Filed: 12/30/1982
  • Issued: 01/08/1985
  • Est. Priority Date: 12/30/1982
  • Status: Expired due to Term
First Claim
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1. A method for determining the position of an instrument on a surface having a plurality of grid conductors oriented in X and Y directions, all X conductors interconnected by resistors, said plurality of X conductors having a pair of terminals, a first X terminal connected to a first X conductor and a second X terminal connected to a last X conductor, all Y conductors interconnected by resistors, said plurality of Y conductors having a pair of terminals, a first Y terminal connected to a first Y conductor and a second Y terminal connected to a last Y conductor, said method comprising the steps:

  • a. generating an electrical signal;

    b. transmitting said signal from said instrument into said surface to cause respective signals to appear at each of said terminals;

    c. forming a ratio of signal levels detected at the X conductor terminals;

    d. generating a digital signal proportional to said ratio to thereby indicate the X position of said instrument;

    e. forming a ratio of signal levels at the Y conductor terminals; and

    f. generating a digital signal proportional to said ratio to thereby indicate the Y position of said instrument.

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