Key circuit

Details Key circuit Key circuit

1986-09-26

1987-10-20

Caldwell, Sr., John W.

Communications: electrical

Audible indication

Percussion-type sound producer

340365R, 307296A, 364707, G06F 302, G06F 104

Patent

active

047017481

ABSTRACT:
A plurality of key switches are provided between each pair of external terminals. A logic circuit generates time-division signals sequentially. The logic circuits stops the generation of these time-division signals during a blanking period with a predetermined time duration, thereby to stop the through-current during this period. The plurality of time-division signals are input to a plurality of buffer circuits. The outputs of the buffer circuits are supplied to the external output. Detection circuits detect only the operated key switches on the basis of the time-division signals and the signals from the external terminals exclusively used for key signal inputting. A plurality of switch members are provided between each of the external terminals and the reference potential. These switch members are conductive during the blanking period to improve the drive capability for external load.

REFERENCES:
patent: 4303907 (1981-12-01), Wilson
patent: 4479191 (1984-10-01), Nojima et al.

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