SOLID STATE KEYBOARD

• US 3,846,791 A
• Filed: 10/02/1972
• Issued: 11/05/1974
• Est. Priority Date: 10/02/1972
• Status: Expired due to Term

• Current Assignee: Richard C. Foster
• Original Assignee: Richard C. Foster
• Inventors: Foster, Richard C.
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/294,038
• Time in Patent Office: 764 Days
• Field of Search: 340/365C 178/17D 197/9K 200/DIG.1 328/5 307/308 317/11C
• US Class Current: 341/33
• CPC Class Codes: H03K 17/9618 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 17/98 having a plurality of control members, e.g. keyboard

Abstract

A solid state keyboard having an array of immobile metal keyrepresenting contacts on an insulative board. The contacts may be formed in the shape of the alphanumeric character or other indicia to be associated therewith. The rear surface of the board may include suitable electronic circuitry, preferably in the form of integrated circuits connected to the contacts by printed circuit traces and plated through holes. The electronic circuitry includes a signal source adapted to supply a high frequency electrical signal to the contacts and threshold detectors connected to each of the contacts. When the finger of the operator makes conductive contact with one of the contacts, the signal level applied to the threshold detector will be reduced, actuating the threshold detector to achieve the desired electronic switching.

Claims

1. A solid state keyboard comprising a plurality of conductive terminals, signal source means for generating a high frequency signal, coupling impedance means connected to each of said terminals for applying said signal to said terminals and sensing means for each of said terminals for sensing a reduction in signal level at the output of said coupling impedance means, the product of the frequency of said signal and the impedance of said coupling impedance means being from about 2 X 109 Hertz-ohms to about 50 X 109 Hertz-ohms so that conductive contact of the operator'"'"''"'"'s finger on said terminal is required to reduce the signal level sufficiently to actuate said sensing means.

2. Apparatus according to claim 1 comprising an insulative board carrying said terminals on one side thereof, said signal source means and said sensing means comprising electronic circuit means having an array of printed circuit traces on the other side of said board and conductive means electrically connecting said terminals and said printed circuit traces.

3. Apparatus according to claim 2, wherein said terminals are formed in the shape of an indicia representative of the function associated with said terminal.

4. Apparatus according to claim 2, wherein said electronic circuit means comprises at least one integrated circuit carried on said other side of said board.

5. Apparatus according to claim 1, further comprising filter means in series with each of said terminals for conducting said signal to said terminals while substantially blocking the conduction of D.C. and 60 Hz from said terminals to said sensing means.

6. Apparatus according to claim 5, wherein said filter means comprises a capacitor.

7. Apparatus according to claim 5, wherein the impedence of said filter means at the frequency of said signal is substantially lower than the impedance of said coupling impedance means.

8. Apparatus according to claim 5, wherein the input impedance of said sensing means is substantially higher than the impedance of said coupling impedance means.

9. Apparatus according to claim 5, wherein each of said coupling impedance means comprises dual impedance means having a lower impedance for current flow in one direction and a higher impedance for current flow in the other direction.