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US3372239A
Expired / Lapsed
US
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Voice-switched interphone system
Assignee: AT&T Inc
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Filing: 1964-07-01
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Granted: 1968-03-05
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Expires: 1984-07-01
Abstract
No abstract record available.
Inventors
- 👤 Frank J Clement
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:06
CPC Classifications
H; H04; H04M; H04M9/00; H04M9/08; H04M9/10
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1971-03-05 | 1971-09-04 | 1972-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1975-03-05 | 1975-09-04 | 1976-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1979-03-05 | 1979-09-04 | 1980-03-05 | $7700.00 | Window Closed / Lapsed |