Interrogation of key switches using pulse width detection

Details Interrogation of key switches using pulse width detection Interrogation of key switches using pulse width detection

1977-09-26

1980-03-18

Caldwell, Sr., John W.

Communications: electrical

Audible indication

Percussion-type sound producer

340305S, G08C 2500, G06F 302

Patent

active

041941888

ABSTRACT:
In a keyboard having two depressable key switches which receive pulses of a first given width and transmit in response thereto pulses whose width is a function of the mechanical travel of the key switch, the travel of the key switches is detected by feeding a pulse of a first given width alternately to the key switches, sensing for the width of pulses transmitted by the key switches in response to receipt of the pulses of first given width. When the width of a pulse transmitted by one of the key switches in response to the receipt of one of the pulses of the first given width exceeds a second given width which is less than the first given width, there is fed a series of the pulses of first given width only to such one key switch and none of the pulses to the other of the key switches. Then, there is indicated that such one key switch has been reliably depressed if for a given period of time all the pulses transmitted by such one key switch in response to the series of pulses have at least the second given width.

REFERENCES:
patent: 3825926 (1974-07-01), Brownback
patent: 3973256 (1976-08-01), Stoesser et al.
patent: 4020391 (1977-04-01), Baxter
patent: 4106011 (1978-08-01), Melanson et al.
patent: 4110748 (1978-08-01), Marino
Electronics, May 15, 1975, pp. 83-85.

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