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Device forming tactile screen of the capacitive type

  • US 5,432,671 A
  • Filed: 08/18/1992
  • Issued: 07/11/1995
  • Est. Priority Date: 02/19/1990
  • Status: Expired due to Fees
First Claim
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1. Device forming a touch screen of the capacitive type for covering a display screen, comprisinga first group of electrically conducting transparent first electrodes insulated from each other, not exposed to the outside,a second group of electrically conducting transparent second electrodes insulated from each other to form front keys, anda substrate of a transparent dielectric material, said second group of electrodes being separated from the first group of electrodes by said transparent dielectric material, the second electrodes of the second group having substantially the same dimensions as the first electrodes of the first group and being superimposed respectively upon the electrodes of the first group while facing one another so as to form capacitors, each capacitor comprising a first electrode and a second electrode in superimposed relationship thereto, the effective capacity of a respective one of said capacitors varying when a body forming a mass reference frame is applied upon a second electrode of said capacitor, the capacitance of the body being in series with each of said capacitors, andan electronic circuit for detecting a variation in capacitance, said circuit being connected only to said first electrodes and not to said second electrodes to detect a variation in effective capacity of any one of said capacitors.

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