US2539556A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Variable delay speech privacy system
Assignee: AT&T Inc
•
Filing: 1941-07-11
•
Granted: 1951-01-30
•
Expires: 1961-07-11
Abstract
No abstract record available.
Inventors
- 👤 John C Steinberg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 23:57
CPC Classifications
H; H04; H04K; H04K1/00; H04K1/02; H04K1/06; H04M; H04M1/00; H04M1/68
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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US2217864A
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US2312897A
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US2301455A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1954-01-29 | 1954-07-31 | 1955-01-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1958-01-29 | 1958-07-31 | 1959-01-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1962-01-29 | 1962-07-31 | 1963-01-30 | $7700.00 | Window Closed / Lapsed |