Patent US2220371A successfully refreshed from Google Patents.
US2220371A
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US
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Electrical signaling system
Assignee: American District Telegraph Co
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Filing: 1937-10-09
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Granted: 1940-11-05
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Expires: 1957-10-09
Abstract
No abstract record available.
Inventors
- 👤 Richard M Hopkins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 21:03
CPC Classifications
H; H04; H04L; H04L12/00; H04L12/28; H04L12/40; G; G08; G08B; G08B25/00; G08B25/01; G08B25/04; G08B25/045
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) | 1943-11-05 | 1944-05-06 | 1944-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1947-11-05 | 1948-05-06 | 1948-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1951-11-05 | 1952-05-06 | 1952-11-05 | $7700.00 | Window Closed / Lapsed |