Patent US1687220A successfully refreshed from Google Patents.
US1687220A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electric-wave producer
Assignee: AT&T Inc
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Filing: 1923-10-16
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Granted: 1928-10-09
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Expires: 1943-10-16
Abstract
No abstract record available.
Inventors
- 👤 Samuel S Mackeown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 20:57
CPC Classifications
H; H03; H03F; H03F1/00; H03F1/02; H03F1/04
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1931-10-09 | 1932-04-09 | 1932-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1935-10-09 | 1936-04-09 | 1936-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1939-10-09 | 1940-04-09 | 1940-10-09 | $7700.00 | Window Closed / Lapsed |