Patent US4170590A successfully refreshed from Google Patents.
Patent US2921138A successfully refreshed from Google Patents.
US2921138A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telephone systems
Assignee: British Telecommunications PLC
•
Filing: 1956-06-05
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Granted: 1960-01-12
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Expires: 1976-06-05
Abstract
No abstract record available.
Inventors
- 👤 Baker George Thomas
- 👤 Smith John Lawley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:40
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/42; H04M3/50; H04M3/51; H04M3/523; H04M15/00; H04M15/04; H04Q; H04Q3/00; H04Q3/42
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US1857833A
Cited
US2298519A
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US2534500A
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US2567812A
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US2620399A
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US2558187A
Cited
US2764634A
Cited
US2679551A
Cited
US2700148A
Cited
US2819345A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1963-01-11 | 1963-07-13 | 1964-01-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1967-01-11 | 1967-07-13 | 1968-01-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1971-01-11 | 1971-07-13 | 1972-01-12 | $7700.00 | Window Closed / Lapsed |