Patent US3369163A successfully refreshed from Google Patents.
US3008014A
Expired / Lapsed
US
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Electrostatic loudspeakers
Assignee: Ferranti International PLC
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Filing: 1957-09-12
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Granted: 1961-11-07
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Expires: 1977-09-12
Abstract
No abstract record available.
Inventors
- 👤 David T N Williamson
- 👤 Peter J Walker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:43
CPC Classifications
H; H04; H04R; H04R19/00; H04R19/02
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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US2855467A
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US2864899A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1964-11-06 | 1965-05-08 | 1965-11-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1968-11-06 | 1969-05-08 | 1969-11-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1972-11-06 | 1973-05-08 | 1973-11-07 | $7700.00 | Window Closed / Lapsed |