Key input circuit

Details Key input circuit Key input circuit

1979-11-14

1981-12-08

Robinson, Thomas A.

Communications: electrical

Audible indication

Percussion-type sound producer

364707, G08C 900, G06F 738

Patent

active

043050654

ABSTRACT:
A key input circuit includes a matrix array of key switches, a scanning signal generator, and an output circuit that provides a key output signal, whenever any of the key switches is depressed, as an indication of the key switch that is so depressed. The key input circuit also includes a gating circuit for selectively enabling the scanning signal generator so that the latter only supplies a scanning signal to the key switches if one of the key switches is depressed, and ceases to supply the scanning signal when all of the key switches are released, thereby eliminating the unnecessary generation of the scanning signal as a source of signal interference.

REFERENCES:
patent: 4109315 (1978-08-01), Pan
patent: 4179588 (1979-12-01), Oliveira
Zabierowski, J., "8 Standard TTLs Form Full ASC11 _Keyboard Encoder" Electronic Engineering, pp. 33-35, Sep. 1978.

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