US2905771A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Piezoresistive semiconductor microphone
Assignee: AT&T Inc
•
Filing: 1957-05-15
•
Granted: 1959-09-22
•
Expires: 1977-05-15
Abstract
No abstract record available.
Inventors
- 👤 Fred P Burns
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:38
CPC Classifications
H; H04; H04R; H04R23/00; H04R23/006
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
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) | 1962-09-21 | 1963-03-23 | 1963-09-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1966-09-21 | 1967-03-23 | 1967-09-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1970-09-21 | 1971-03-23 | 1971-09-22 | $7700.00 | Window Closed / Lapsed |