Patent US3553687A successfully refreshed from Google Patents.
US3553687A
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US
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Alarm system sensitive to cut cables and insensitive to r-f interference
Assignee: Alarmtronics Engineering Inc
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Filing: 1968-06-03
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Granted: 1971-01-05
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Expires: 1988-06-03
Abstract
Abstract IN AN ALARM SYSTEM WITH A BALANCED SHIELDED MICROPHONE CABLE A BARE DRAIN WIRE IS TIED TO THE CABLE SHIELD AT THE END OF THE MICRPHONE CABLE, THE END MICROPHONE BEING TERMINATED WITH RESISTORS SO THAT CABLE CUT BRIDGE CIRCUIT DETECTS AN UNBALANCE WHEN ANY MICROPHONE CABLE IS CUT TO PROVIDE AN ALARM SIGNAL AND REDUCE R-F INTERFERENCE.
Inventors
- 👤 Martin H Reiss
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:41
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/16; G08B13/1654; G08B13/169
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) | 1974-01-04 | 1974-07-06 | 1975-01-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-01-04 | 1978-07-06 | 1979-01-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-01-04 | 1982-07-06 | 1983-01-05 | $7700.00 | Window Closed / Lapsed |