US3749940A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Keyboard strobe filter for static keyboards
Assignee: Unisys Corp
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Filing: 1972-04-21
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Granted: 1973-07-31
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Expires: 1992-04-21
Abstract
Abstract A keyboard strobe system for a static keyboard which strobes the generated code only once for a single key depression whatever the number of contact bounces or overshoots affecting a static strobe signal. The strobe pulse for each contact closure is clocksynchronized. The system comprises a digital signal processing circuit having two retriggerable delay multivibrators, two J-K flip-flops and a plurality of logic gates.
Inventors
- 👤 G Maitrias
- 👤 P Diepart
- 👤 P Gransart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 17:16
CPC Classifications
H; H03; H03K; H03K3/00; H03K3/01; H03K3/013; H03M; H03M11/00; H03M11/02
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
180 words
A digital signal processing circuit capable of producing a single clock-synchronized strobe pulse in response to an input signal from a SPST contact, said processing circuit comprising a first retriggerable delay multivibrator with an input and an output, the input of said first retriggerable delay multivibrator receiving the positive transition of the strobe signal from the keyboard contact; a second retriggerable delay multivibrator with an input and an output, the input of said second retriggerable delay multivibrator receiving the negative transition of the strobe signal from the keyboard contact; an OR gate with two inputs and an output, said OR gate inputs receiving respectively the outputs from the first and second retriggerable delay multivibrators; a four machine state loop having three inputs and an output, a first input of said loop receiving the output from said OR gate, a second input of said loop receiving the strobe signal directly from the SPST contact and a third input of said loop receiving a master clock signal, said four machine state loop producing at the output thereof a code strobe time pulse.
Claim 2
Dependent Claim
180 words
A digital signal processing circuit capable of producing a single clock-synchronized strobe pulse in response to an input signal from a SPST contact, said processing circuit comprising a first retriggerable delay multivibrator with an input and an output, the input of said first retriggerable delay multivibrator receiving the positive transition of the strobe signal from the keyboard contact; a second retriggerable delay multivibrator with an input and an output, the input of said second retriggerable delay multivibrator receiving the negative transition of the strobe signal from the keyboard contact; an OR gate with two inputs and an output, said OR gate inputs receiving respectively the outputs from the first and second retriggerable delay multivibrators; a four machine state loop having three inputs and an output, a first input of said loop receiving the output from said OR gate, a second input of said loop receiving the strobe signal directly from the SPST contact and a third input of said loop receiving a master clock signal, said four machine state loop producing at the output thereof a code strobe time pulse.
Claim 3
Dependent Claim
36 words
The processing circuit as set forth in claim 1, wherein the four machine state loop comprises two J-K flip-flops, to code said loop, said J-K flip-flops receiving at the C input thereof the master clock signal.
Claim 4
Dependent Claim
31 words
The processing circuit as set forth in claim 1, wherein said first and second retriggerable delay multivibrators are so adjusted that the period thereof covers the minimum acceptable strobe signal duration.
Claim 5
Dependent Claim
19 words
The processing circuit as set forth in claim 1, wherein said SPST contact is part of a static keyboard.
References Cited (Backward Citations)
US3471789A
Cited
US3508079A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-30 | 1977-01-29 | 1977-07-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-30 | 1981-01-29 | 1981-07-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-30 | 1985-01-29 | 1985-07-31 | $7700.00 | Window Closed / Lapsed |