Circuit arrangement for a keyboard

Details Circuit arrangement for a keyboard Circuit arrangement for a keyboard

1979-02-23

1980-11-18

Robinson, Thomas A.

Communications: electrical

Audible indication

Percussion-type sound producer

340166R, G06F 302

Patent

active

042348722

ABSTRACT:
A circuit arrangement for a keyboard is disclosed, in which the switches of the keyboard are each connected in series with a respective LED to form a switch matrix, the rows of which are connected to a multiplexer and the colums of which are connected to an evaluation device. The LED's serve as decoupling diodes, and furthermore form a diode matrix of an optical indication field by which the commands entered into the keyboard through activation of its switches, or other information, can be made optically visible. Upon activation of a transistor switch, a resistor is switched parallel to a measurement resistor, whereby an LED is lighted at the point of intersection of the activated matrix row and matrix column.

REFERENCES:
patent: 3732389 (1973-05-01), Kaelin et al.
patent: 3811025 (1974-05-01), Bach
patent: 3990070 (1976-11-01), Spence
patent: 4065754 (1977-12-01), Miura et al.
patent: 4077036 (1978-02-01), Avakian et al.
patent: 4092640 (1978-05-01), Satoh
"Scanned Optical Keyboard", J. E. Fox, IBM Tech. Dis. Bull'n., vol. 20, No. 9, Feb. 1978, pp. 3615-3616.

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