US2993090A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrostatic speaker circuit
Assignee: ARF Products Inc
•
Filing: 1955-03-16
•
Granted: 1961-07-18
•
Expires: 1975-03-16
Abstract
No abstract record available.
Inventors
- 👤 Julius J Hupert
- 👤 Andrzej B Przedpelski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 14:10
CPC Classifications
H; H04; H04R; H04R19/00; H04R19/02
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
US1674683A
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US1862931A
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US2040954A
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US1961329A
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US2167462A
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US2474191A
Cited
US2616970A
Cited
US2631197A
Cited
US2697755A
Cited
FR1091147A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1964-07-17 | 1965-01-16 | 1965-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1968-07-17 | 1969-01-16 | 1969-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1972-07-17 | 1973-01-16 | 1973-07-18 | $7700.00 | Window Closed / Lapsed |