US2875281A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Telephone ringing system
Assignee: AT&T Inc
•
Filing: 1954-03-08
•
Granted: 1959-02-24
•
Expires: 1974-03-08
Abstract
No abstract record available.
Inventors
- 👤 Mark A Townsend
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 13:26
CPC Classifications
H; H04; H04Q; H04Q5/00
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US1795389A
Cited
US2004244A
Cited
US2088311A
Cited
US2268880A
Cited
US2261620A
Cited
US2408299A
Cited
GB749998A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1962-02-23 | 1962-08-25 | 1963-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1966-02-23 | 1966-08-25 | 1967-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1970-02-23 | 1970-08-25 | 1971-02-24 | $7700.00 | Window Closed / Lapsed |