US3928847A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fast scan electronic circuit with contact bounce elimination for an automatic typing system keyboard
Assignee: CPT CORP
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Filing: 1974-02-04
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Granted: 1975-12-23
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Expires: 1994-02-04
Abstract
Abstract The present invention relates to a keyboard for a typing system. The keys are connected to a sixteen by eight matrix. The input to the matrix is provided by a one of sixteen decoder and the output by a one of eight multiplexer. The specific positions of the decoder and multiplexer are determined by a character counter which generates the keyboard code and ultimately a keyboard strobe to print the character designed by the keyboard code. As the keyboard strobe is generated a data bit corresponding to that keyboard code location is entered in parallel in four memory units to create an inhibit for the keyboard strobe so that continued depression of the key without release does not cause a multiple character print-out by the print mechanism. After the key has been released each memory location is then serially cleared with a reset timer to assure that contact bounce or the like does not prematurely clear the memory and enable an additional keyboard strobe.
Inventors
- 👤 Gary W Spence
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 21:35
CPC Classifications
H; H03; H03M; H03M11/00; H03M11/20
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
260 words
A keyboard circuit comprising: a plurality of conducting means; a plurality of continuity switches having contacts for selectively interconnecting two of the conducting means; counting means for establishing a keyboard code; sensing means connected to the conducting means and connected to and controlled by the counting means for sequentially interrogating in accordance with the keyboard code the conducting means to determine whether two of the conducting means have been interconnected or disconnected by an operator of the continuity switches and for providing an output signal when two of the conducting means have been interconnected by one of the continuity switches; means responsive to the output signal for generating a keyboard strobe signal; storage means operatively connected to the counting means and connected to the sensing means, the storage means comprising at least two memory locations for each keyboard code, for recording the interconnection of two of the conducting means by the selected continuity switch wherein the output signal is electronically recorded in parallel in each memory location corresponding to the selected continuity switch said storage means also being connected to the means for generating a keyboard strobe signal for inhibiting the means for generating a keyboard strobe signal until all memory locations for the selected keyboard code have been cleared; and time delay means connected to the storage means for sequentially clearing each memory location for the selected keyboard code, each memory location being serially cleared after time intervals determined by the time delay means after the selected continuity switch has been disconnected by the operator of the continuity switcheS.
Claim 2
Dependent Claim
260 words
A keyboard circuit comprising: a plurality of conducting means; a plurality of continuity switches having contacts for selectively interconnecting two of the conducting means; counting means for establishing a keyboard code; sensing means connected to the conducting means and connected to and controlled by the counting means for sequentially interrogating in accordance with the keyboard code the conducting means to determine whether two of the conducting means have been interconnected or disconnected by an operator of the continuity switches and for providing an output signal when two of the conducting means have been interconnected by one of the continuity switches; means responsive to the output signal for generating a keyboard strobe signal; storage means operatively connected to the counting means and connected to the sensing means, the storage means comprising at least two memory locations for each keyboard code, for recording the interconnection of two of the conducting means by the selected continuity switch wherein the output signal is electronically recorded in parallel in each memory location corresponding to the selected continuity switch said storage means also being connected to the means for generating a keyboard strobe signal for inhibiting the means for generating a keyboard strobe signal until all memory locations for the selected keyboard code have been cleared; and time delay means connected to the storage means for sequentially clearing each memory location for the selected keyboard code, each memory location being serially cleared after time intervals determined by the time delay means after the selected continuity switch has been disconnected by the operator of the continuity switcheS.
Claim 3
Dependent Claim
32 words
The keyboard circuit of claim 1 wherein the storage means comprises a multiple stage shift register, each stage of the multiple stage shift register having a memory location for each keyboard code.
Claim 4
Dependent Claim
80 words
The keyboard circuit of claim 2 wherein a data flip flop is connected to the multiple stage shift register and to the means for generating the selected keyboard strobe signal which, when it is set, enters into each memory location in parallel a data bit corresponding to the keyboard code for the selected keyboard strobe signal and wherein the time delay means comprises a reset timer which is utilized to successively clear the appropriate bit location in each memory location.
Claim 5
Dependent Claim
37 words
The keyboard circuit of claim 3 wherein the reset timer is synchronized with the counting means and wherein the reset timer operates to clear information bits from each memory location upon specified cycles of the counting means.
Claim 6
Dependent Claim
56 words
The keyboard circuit of claim 3 wherein the reset timer is operatively connected to the multiple stage shift register and serially clears the bits from each memory location within a timing interval which is greater than the time necessary to eliminate contact bounce, but less than the physical reaction time of the operator of the keyboard.
Claim 7
Dependent Claim
124 words
The keyboard circuit of claim 1 wherein the plurality of conducting means comprises a matrix having a plurality of first and second conducting elements and wherein the sensing means comprise decoding means connected to the first conducting elements and connected to and controlled by the counting means for sequentially establishing a signal on each of the first conducting elements in accordance with the count in the counting means; and multiplexing means connected to the second conducting elements and connected to and controlled by the counting means for sequentially determining in accordance with the count in the counting means whether a signal has been established on any of the second conducting elements from one of the first conducting elements through one of the continuity switches.
Claim 8
Dependent Claim
27 words
The keyboard circuit of claim 1 further comprising register means for monitoring the counting means to determine in accordance with the keyboard code the selected continuity switch.
Claim 9
Dependent Claim
35 words
The keyboard circuit of claim 1 further comprising clocking means to synchronize the counting means and the storage means and to establish the rate at which the sensing means will sequentially interrogate the conducting means.
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) | 1978-12-22 | 1979-06-23 | 1979-12-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-22 | 1983-06-23 | 1983-12-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-22 | 1987-06-23 | 1987-12-23 | $7700.00 | Window Closed / Lapsed |