US4414538A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Keyboard sense gate
Assignee: AT&T Teletype Corp
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Filing: 1981-12-07
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Granted: 1983-11-08
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Expires: 2001-12-07
Abstract
Abstract Twenty-five capacitive keyswitches 16a-e are arranged in a matrix having five row conductors 12a-e and five column conductors 14a-e. A series of five pulses are fed to each row conductor 14a-e in succession through AND gates 41a-e controlled by a counter 34. Each time a row conductor 12a-e is pulsed, all of the column conductors 14a-e are scanned. When one of the column conductors 14a-e is scanned, the associated coupling transistor 54a-e is turned on and the associated discharge transistor 50a-e is turned off. The remaining coupling transistor 54a-e of the remaining columns 14a-e are off and the remaining discharge transistors 50a-e are on.
Inventors
- 👤 Paul G. Schnizlein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 07:31
CPC Classifications
H; H03; H03M; H03M11/00; H03M11/20
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
247 words
A circuit for scanning a plurality of keyswitches (16a-y) arranged in a matrix having a plurality of row conductors (12a-e) and a plurality of column conductors (14a-e), each of said row conductors (12a-e) being sequentially energized so that upon actuation of a keyswitch (16a-y) connecting an energized row conductor, a signal is coupled to a corresponding one of the column conductors (14a-e); a plurality of sense gates (22a-e) each of which is associated with one of the column conductors (14a-e), each of said column sense gates (22a-e) comprising: means (50a-e) when placed in a dicharge mode for selectively discharging, in response to a first control signal, any signal present upon the associated column conductor (14a-e); means (54a-e) when placed in a conductive mode for selectively coupling, in response to a second control signal, any signal upon the associated column conductor (14a-e) to a sense conductor (24), said selective discharge means (50a-e) and said coupling means (54a-e) being alternatively operative; means (18) for sequentially supplying said second control signals to said column sense gates (22a-e) so as to sequentially place said coupling means (54a-e) of each of said sense gates (22a-e) in the coupling mode and for placing the remaining sense gates (22a-) in the discharge mode; and a coding circuit (60, 62, 64, 66) responsive to signals identifying the matrix position of a keyswitch (16a-y) location currently being scanned and to the signal upon said sense conductor (24) for generating a coded representation of the actuated keyswitch.
Claim 2
Dependent Claim
247 words
A circuit for scanning a plurality of keyswitches (16a-y) arranged in a matrix having a plurality of row conductors (12a-e) and a plurality of column conductors (14a-e), each of said row conductors (12a-e) being sequentially energized so that upon actuation of a keyswitch (16a-y) connecting an energized row conductor, a signal is coupled to a corresponding one of the column conductors (14a-e); a plurality of sense gates (22a-e) each of which is associated with one of the column conductors (14a-e), each of said column sense gates (22a-e) comprising: means (50a-e) when placed in a dicharge mode for selectively discharging, in response to a first control signal, any signal present upon the associated column conductor (14a-e); means (54a-e) when placed in a conductive mode for selectively coupling, in response to a second control signal, any signal upon the associated column conductor (14a-e) to a sense conductor (24), said selective discharge means (50a-e) and said coupling means (54a-e) being alternatively operative; means (18) for sequentially supplying said second control signals to said column sense gates (22a-e) so as to sequentially place said coupling means (54a-e) of each of said sense gates (22a-e) in the coupling mode and for placing the remaining sense gates (22a-) in the discharge mode; and a coding circuit (60, 62, 64, 66) responsive to signals identifying the matrix position of a keyswitch (16a-y) location currently being scanned and to the signal upon said sense conductor (24) for generating a coded representation of the actuated keyswitch.
Claim 3
Dependent Claim
73 words
The circuit of claim 1 wherein said discharing means comprises a discharge transistor connected between the associated column conductor (16a-e) and the common potential of the circuit, said discharge transistor (50a-e) being responsive to said first control signal; and said coupling means comprising a coupling transistor (54a-e) connected between the associated column conductor (16a-e) and said sense conductor (24) and said coupling transistor being rendered conductive in response to said second control signal.
Claim 4
Dependent Claim
42 words
The circuit of claim 2 wherein said first control signal is connected directly to said coupling transistor (54a-e), said second control signal is the inversion of said first control signal and said second control signal is coupled to said discharge transistor (50a-e).
Claim 5
Dependent Claim
14 words
The circuit of claims 1, 2, or 3 wherein said keyswitches (16a-e) are capacitive.
Claim 6
Dependent Claim
52 words
The circuit of claim 2 wherein said first and second control signals are generated by a column address counter (20) and said short duration signal is switched to each of said rows by a row address counter (34), said column address counter (26) scanning each of said columns for each row address.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-07 | 1987-05-09 | 1987-11-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-07 | 1991-05-09 | 1991-11-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-07 | 1995-05-09 | 1995-11-08 | $7700.00 | Window Closed / Lapsed |