Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1977-09-29
1979-07-31
Caldwell, Sr., John W.
Communications: electrical
Audible indication
Percussion-type sound producer
200DIG1, 340365L, 4004791, G06F 302
Patent
active
041632222
ABSTRACT:
For capacitance coupled keyboard data entry means, a key switch, synchronous circuitry and phase detector in combination to yield a unique encoder output signal for a keyboard matrix. Capacitance coupling is effected prior to full key switch travel, that is, coupling actuation prior to full key downtravel and deactuation subsequent to manual key switch release, said key switch having a floating electrical coupling plate inhibited from dropping to a printed circuit board by a fixably positioned magnet. Coupling actuation providing mechanical hysterisis is effected upon key depression by a spring forcing said plate from the magnet and deactuation is effected by the magnet retracting said plate. An analog multiplexer, in synchronization with an encoder are driven by clock counter means to scan the keyboard matrix. The counter further provides distinct high frequency pulse bursts to an actuated coupled connection. High frequency analog multiplexed key switch signals are amplified and transferred upon a single line string having a phase detector in synchronization with the system. The phase detector compares an actuated key reference signal phase to the phase of an actuated key multiplexed signal filtering the latter, the reference phase being derived from said high frequency pulse bursts fed an actuated coupled key switch connection.
REFERENCES:
patent: 3623082 (1971-11-01), Stein et al.
patent: 3696908 (1972-10-01), Gluck et al.
patent: 3797630 (1974-03-01), Zilkha
patent: 3931610 (1976-01-01), Marin et al.
Amkey, Incorporated
Caldwell Sr. John W.
Cannon, Jr. James J.
Groody James J.
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