Patent US2957950A successfully refreshed from Google Patents.
US2957950A
Expired / Lapsed
US
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Transistor selective ringing circuit
Assignee: AT&T Inc
•
Filing: 1954-11-18
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Granted: 1960-10-25
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Expires: 1974-11-18
Abstract
No abstract record available.
Inventors
- 👤 Erwin W Holman
- 👤 William C Schmidt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 08:34
CPC Classifications
H; H04; H04Q; H04Q5/00; H04M; H04M19/00; H04M19/02; H04M19/04
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US2343759A
Cited
US2658112A
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US2686227A
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US2654002A
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US2642500A
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US2889410A
Cited
US2824175A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1963-10-25 | 1964-04-25 | 1964-10-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1967-10-25 | 1968-04-25 | 1968-10-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1971-10-25 | 1972-04-25 | 1972-10-25 | $7700.00 | Window Closed / Lapsed |