Browse Prior Art Database

Touch Actuated Keyboard

IP.com Disclosure Number: IPCOM000085713D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Nassimbene, EG: AUTHOR

Abstract

This touch keyboard is compact, reliable and can be implemented as an overlay coordinate data input device.

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Touch Actuated Keyboard

This touch keyboard is compact, reliable and can be implemented as an overlay coordinate data input device.

A rectangular grid is arranged of elongated conductors spaced apart by 0.635 cm (1/4 inch) and insulated from each other. Each square or "cell" of the grid is defined by two horizontal and two vertical conductors which are located within the span of the average finger pad, as indicated by the shaded outline 10. Logical circuitry is arranged to resolve each actuation.

A keyboard for a four-operation electronic calculator application comprises horizontal conductors 11,12...16 and vertical conductors 21,22 ...25 which are insulated from each other. Successive pairs of conductors are associated by AND gating circuits 31-35 and 41-44. These gating circuits are conventional but chosen so that any unilateral conducting elements (diodes, for example) are properly poled for direct-current flow as later defined. Each AND gating circuit 31-33 is connected to a sensing circuit 51, of which only one is shown. The AND gating circuits 41-44 are each connected to a similar sensing circuit 63, only one of which is shown.

The base electrode 56 of the input transistor 58 is held positive until a selection is made on the keyboard by a finger touching conductors 11,12 and 23,24 as indicated by the shaded outline 10. This brings the base electrode 66 of transistor 68 to ground through a resistor 60 in the base bias circuit for the input transistor 66 of the sensing circuit 63. At the same time the base electrode 56 of the input transistor 58 is co...