US2721935A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Duplex radio telephone system
Assignee: AT&T Inc
•
Filing: 1951-12-28
•
Granted: 1955-10-25
•
Expires: 1971-12-28
Abstract
No abstract record available.
Inventors
- 👤 Louis A Dorff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:27
CPC Classifications
H; H04; H04W; H04W84/00; H04W84/02
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US1572756A
Cited
US2061699A
Cited
US2472585A
Cited
US2501091A
Cited
US2503727A
Cited
US2623164A
Cited
US2599097A
Cited
US2530815A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1958-10-24 | 1959-04-25 | 1959-10-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1962-10-24 | 1963-04-25 | 1963-10-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1966-10-24 | 1967-04-25 | 1967-10-25 | $7700.00 | Window Closed / Lapsed |