US3021398A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Continuous checking of circuit continuity of a signaling system
Assignee: AT&T Inc
•
Filing: 1960-05-26
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Granted: 1962-02-13
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Expires: 1980-05-26
Abstract
No abstract record available.
Inventors
- 👤 Cecil H Barnett
- 👤 Wayne V K Large
- 👤 Harold M Pruden
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:15
CPC Classifications
H; H04; H04M; H04M3/00; H04M3/22; H04M3/26; H04M3/28
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) | 1965-02-12 | 1965-08-14 | 1966-02-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1969-02-12 | 1969-08-14 | 1970-02-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1973-02-12 | 1973-08-14 | 1974-02-13 | $7700.00 | Window Closed / Lapsed |