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Coordinate input system and input implement used in the system

DC
  • US 5,134,689 A
  • Filed: 08/24/1988
  • Issued: 07/28/1992
  • Est. Priority Date: 08/24/1987
  • Status: Expired due to Term
First Claim
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1. A method of determining the position of an implement on a tablet and the pressure of the implement on a surface of the tablet, the implement including a tuned circuit with a predetermined resonant frequency and a pressure responsive reactance connected in circuit with the tuned circuit, the pressure responsive reactance having a value that changes as a function of the pressure of the implement on the surface of the tablet, the tablet including coils arranged in two coordinate directions, comprising the steps of:

  • sequentially exciting at least some of the coils with AC energy having approximately the same frequency as the resonant frequency, the tuned circuit interacting with the AC energy to change the AC current flowing in at least some of the coils so the AC current change at the resonant frequency in at least some of the coils arranged in the two coordinate directions designates the implement position on the tablet and the pressure of the implement on the surface, the AC current change designating the implement on the surface being derived from the same coils of the tablet; and

    responding to the changes in the AC current flowing in said same coils that designate the implement position on the tablet and the pressure of the implement on the surface to indicate the implement position and the pressure of the implement on the surface at positions indicated by the implement on the surface.

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