Patent US3668660A successfully refreshed from Google Patents.
US3668660A
Expired / Lapsed
US
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Touch wire displays
Assignee: Plessey Handel und Investments AG
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Filing: 1970-12-16
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Granted: 1972-06-06
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Expires: 1990-12-16
Abstract
Abstract Each touch-wire contact is connected, by a screened cable in series with a resistor and a 150 K Hz sine wave produced by the generator. A field-effect transistor detection circuit is connected across the resistor. The transistor is not provided with bias and is thus normally cut-off. When a human finger touches the touch-wire contact an a.c. waveform is applied to the base of the transistor causing it to conduct. An important feature of the circuit is the connection of the screen of the screened lead to the generator thereby preventing the cable capacitance from shunting the touch mechanism.
Inventors
- 👤 Laurence Ernest Watten
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 09:20
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/96; H03K17/962; H03K17/965; H03K17/975; H03K17/98
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
150 words
An electronically responsive manual keyboard system comprising: a plurality of human touch activated keyboard contact means arranged electrically in pairs, a plurality of alternating current driven capacitance bridge circuits each having its capacitative arms formed by a circuit including one of a pair of said touch activated contact means, a plurality of two-input differential amplifiers each individually connected as a bridge detector circuit and arranged to provide (1) a first output condition when a particular one of a pair of touch activated contacts is activated, (ii) a second output condition when the other of said pair of touch activated contacts is activated and (iii) a null output condition when neither of said pair of touch activated contacts are activated and a binary coding arrangement to which the outputs from all of said differential amplifiers are connected and adapted to produce a binary coded indication of an activated touch contact means.
Claim 2
Dependent Claim
150 words
An electronically responsive manual keyboard system comprising: a plurality of human touch activated keyboard contact means arranged electrically in pairs, a plurality of alternating current driven capacitance bridge circuits each having its capacitative arms formed by a circuit including one of a pair of said touch activated contact means, a plurality of two-input differential amplifiers each individually connected as a bridge detector circuit and arranged to provide (1) a first output condition when a particular one of a pair of touch activated contacts is activated, (ii) a second output condition when the other of said pair of touch activated contacts is activated and (iii) a null output condition when neither of said pair of touch activated contacts are activated and a binary coding arrangement to which the outputs from all of said differential amplifiers are connected and adapted to produce a binary coded indication of an activated touch contact means.
Claim 3
Dependent Claim
48 words
An electronically responsive manual keyboard system as defined in claim 1 wherein each of said pairs of human touch activated contact means are connected to the inputs of said differential amplifiers by way of co-axial leads the screens of which are connected to the source of alternating current.
References Cited (Backward Citations)
GB846018A
Cited
US3293640A
Cited
US3437795A
Cited
US3482241A
Cited
GB1185676A
Cited
US3492440A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-06 | 1975-12-06 | 1976-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-06 | 1979-12-06 | 1980-06-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-06 | 1983-12-06 | 1984-06-06 | $7700.00 | Window Closed / Lapsed |