US1616639A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High-frequency sound-transmission system
Assignee: AT&T Inc
•
Filing: 1921-06-03
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Granted: 1927-02-08
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Expires: 1941-06-03
Abstract
No abstract record available.
Inventors
- 👤 Clarence A Sprague
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:05
CPC Classifications
E; E04; E04B; E04B1/00; E04B1/99; G; G10; G10K; G10K15/00; G10K15/02
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) | 1930-02-07 | 1930-08-09 | 1931-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1934-02-07 | 1934-08-09 | 1935-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1938-02-07 | 1938-08-09 | 1939-02-08 | $7700.00 | Window Closed / Lapsed |