Patent US1638925A successfully refreshed from Google Patents.
US1638925A
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US
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High-frequency signaling system
Assignee: AT&T Inc
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Filing: 1922-08-16
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Granted: 1927-08-16
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Expires: 1942-08-16
Abstract
No abstract record available.
Inventors
- 👤 Espenschied Lloyd
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 21:52
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/38; H04B1/40; H04B1/50
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) | 1930-08-15 | 1931-02-14 | 1931-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1934-08-15 | 1935-02-14 | 1935-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1938-08-15 | 1939-02-14 | 1939-08-16 | $7700.00 | Window Closed / Lapsed |