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EL-PC Keyboard

IP.com Disclosure Number: IPCOM000098363D
Original Publication Date: 1960-Aug-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Astrahan, MM: AUTHOR

Abstract

The electroluminescent photoconductor keyboard has a memory function to provide a visual indication of the last key touched. The circuit is energized from a voltage source 1 through a resistor 5. The EL-PC latch circuits 2, 3 and 4 each have an electroluminescent light source 2a, 3a and 4a, a photoconductor 2b, 3b and 4b, and a key operated switch 2c, 3c and 4c.

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EL-PC Keyboard

The electroluminescent photoconductor keyboard has a memory function to provide a visual indication of the last key touched. The circuit is energized from a voltage source 1 through a resistor 5. The EL-PC latch circuits 2, 3 and 4 each have an electroluminescent light source 2a, 3a and 4a, a photoconductor 2b, 3b and 4b, and a key operated switch 2c, 3c and 4c.

The high dark resistance of the photoconductors prevents any of the electroluminescent sources from emitting light when the circuit is initially energized. When one of the keys 2c is depressed, the increased voltage across the corresponding electroluminescent source 2a causes it to glow. The reduced resistance of the photoconductor 2b maintains the voltage across the electroluminescent source at a level sufficient to maintain it in the illuminated condition.

Depressing a second key 4c extinguishes the previously illuminated latch due to the greater drop across resistor 5 caused by the additional current for the second electroluminescent source 4a.

Because of the drop across photoconductor 2b, the voltage across electroluminescent source 2a is substantially lower than the voltage across electroluminescent source 4a, where the photoconductor is shunted by key 4c. It is this voltage differential which transfers the glow as the keys are successively actuated.

In the keyboard construction (lower drawing) a transparent insulating plate 11 supports EL-PC latches 2 and 3. A transparent flexible she...