Patent US1570741A successfully refreshed from Google Patents.
US1570741A
Expired / Lapsed
US
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Testing system for machine-switching circuits
Assignee: AT&T Inc
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Filing: 1923-08-25
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Granted: 1926-01-26
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Expires: 1943-08-25
Abstract
No abstract record available.
Inventors
- 👤 William H Harden
- 👤 Michael A Graefenecker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 19:02
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) | 1929-01-25 | 1929-07-27 | 1930-01-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1933-01-25 | 1933-07-27 | 1934-01-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1937-01-25 | 1937-07-27 | 1938-01-26 | $7700.00 | Window Closed / Lapsed |