Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1981-02-19
1983-06-28
Curtis, Marshall M.
Communications: electrical
Audible indication
Percussion-type sound producer
340711, 400477, G11C 1900
Patent
active
043908667
ABSTRACT:
A keyboard having a plurality of selectively operable matrix elements, each having an actuated and an unactuated state. The state of each matrix element is sequentially scanned and sensed and temporarily stored in a memory. A level detector is coupled to the matrix elements and to the memory means for comparison of the sensed state to a threshold level and for producing an output representative of each comparison. Feedback circuitry is coupled to the memory means for transmitting a feedback signal representative of the previous scan state of each matrix element. The level detector responds to the feedback signal to vary the relative levels of each of the sensed states and its respective threshold level in response to the previous scan state of the matrix element currently scanned.
REFERENCES:
patent: 3648117 (1972-03-01), Yamamoto et al.
patent: 3745536 (1973-07-01), Klehm, Jr.
patent: 3750113 (1973-07-01), Cencel
patent: 3918051 (1975-11-01), Bernin et al.
patent: 4037225 (1977-07-01), De Vall
Buckman Thomas W.
Curtis Marshall M.
Illinois Tool Works Inc.
Mondul Donald D.
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