Patent US4608509A successfully refreshed from Google Patents.
US2808472A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Audio frequency amplifier with variable frequency characteristic
Assignee: US Philips Corp
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Filing: 1954-07-08
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Granted: 1957-10-01
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Expires: 1974-07-08
Abstract
No abstract record available.
Inventors
- 👤 Meewezen Willem Douwe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 07:43
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/189
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US2000505A
Cited
US2178072A
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US2186571A
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US2210997A
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US2264715A
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GB516358A
Cited
US2383867A
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GB668232A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1960-09-30 | 1961-04-01 | 1961-10-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1964-09-30 | 1965-04-01 | 1965-10-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1968-09-30 | 1969-04-01 | 1969-10-01 | $7700.00 | Window Closed / Lapsed |