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Input keyboard for an electronic appliance in entertainment electronics

  • US 5,164,697 A
  • Filed: 04/03/1991
  • Issued: 11/17/1992
  • Est. Priority Date: 04/11/1990
  • Status: Expired due to Fees
First Claim
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1. An input keyboard for an electronic appliance in entertainment electronicswith pushbuttons guided at right angles to the keyboard cover plate (23) and an insulating printed circuit board carrying, in positions correlated with the pushbuttons, contact linings that are to be electrically connected,and with switching devices situated between the pushbuttons and the insulating printed circuit board, where each of the switching devices is correlated with one of the pushbuttons and contains a countercontact that, whenever the pushbutton correlated with the switching device is in its depressed position, will provide a large area of electrical connection between the correlated contact linings,whereinthe countercontact (16) contains a carbonized plastic foil (14) of high electrical resistance that bears against an insulating edge (26) arranged between the printed circuit board (10) and the plastic foil and surrounding the area of the contact linings (11.1, 11.2) correlated with the pushbutton (22), the plastic foil having a certain, though very small electrical conductivity and a thickness (d) that is very small as compared with the distance (a) between the contact linings correlated with the appropriate pushbutton that are to be electrically connected,on the side of the carbonized carbon foil facing away from the contact linings there is arranged an electrically conducting layer (17) having an electrical conductivity that is very great as compared with the electrical conductivity of the carbonized plastic foil, andthe contact linings (11.1, 11.2) correlated with a given pushbutton are connected to a control circuit arrangement (6) for converting bridging resistance (Rk) of the switching device (3) into a control command (Bf, Bw) that determines both a control or adjustment function and a control or adjustment variable, the bridging resistance depending on the pressure (P) that the depressed pushbutton (22) exerts on the countercontact (16) of that pushbutton.

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