Patent US3440351A successfully refreshed from Google Patents.
US3440351A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telephone transmitter circuit employing variable capacitance microphone
Assignee: AT&T Inc
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Filing: 1966-09-09
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Granted: 1969-04-22
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Expires: 1986-09-09
Abstract
No abstract record available.
Inventors
- 👤 Harry J Boll
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:15
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/30; H03F1/302
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US2532060A
Cited
US3005956A
Cited
US3199041A
Cited
US3372235A
Cited
US3393328A
Cited
US3383612A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1972-04-21 | 1972-10-21 | 1973-04-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1976-04-21 | 1976-10-21 | 1977-04-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1980-04-21 | 1980-10-21 | 1981-04-22 | $7700.00 | Window Closed / Lapsed |