Patent US3797008A successfully refreshed from Google Patents.
US3797008A
Expired / Lapsed
US
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Fire detecting system
Assignee: Nittan Co Ltd
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Filing: 1972-01-21
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Granted: 1974-03-12
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Expires: 1992-01-21
Abstract
Abstract A fire detecting system having a voltage source, a pair of conductors extending from the source with a plurality of fire detectors connected across the conductors, means at the end of said conductors placing a constant load on the voltage source and means adjoining the voltage source for detecting loss of said load resulting from a break in one of said conductors.
Inventors
- 👤 H Yuasa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:14
CPC Classifications
G; G08; G08B; G08B25/00; G08B25/01; G08B25/018
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
169 words
A fire detecting system comprising a voltage source, a pair of conductors extending from both terminals of said voltage source, a plurality of fire detectors connected in parallel between said pair of conductors, each detector being provided with switch means for short-circuiting said pair of conductors upon actuation, a first alarm and means for sensing an increase in the current flowing through said conductors and actuating said first alarm, a first zener diode connected between the other ends of said pair of conductors, a disconnection monitor including a second zener diode connected between said pair of conductors, a second alarm, means interconnected with said second zener diode for sensing an increAse in the current flowing through said second zener diode, and a connection between the last said means and said second alarm to actuate said second alarm, the zener voltage of said second zener diode being selected to be higher than the zener voltage of said first zener diode but lower than the terminal voltage of said voltage source.
Claim 2
Dependent Claim
169 words
A fire detecting system comprising a voltage source, a pair of conductors extending from both terminals of said voltage source, a plurality of fire detectors connected in parallel between said pair of conductors, each detector being provided with switch means for short-circuiting said pair of conductors upon actuation, a first alarm and means for sensing an increase in the current flowing through said conductors and actuating said first alarm, a first zener diode connected between the other ends of said pair of conductors, a disconnection monitor including a second zener diode connected between said pair of conductors, a second alarm, means interconnected with said second zener diode for sensing an increAse in the current flowing through said second zener diode, and a connection between the last said means and said second alarm to actuate said second alarm, the zener voltage of said second zener diode being selected to be higher than the zener voltage of said first zener diode but lower than the terminal voltage of said voltage source.
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) | 1977-03-11 | 1977-09-10 | 1978-03-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-11 | 1981-09-10 | 1982-03-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-11 | 1985-09-10 | 1986-03-12 | $7700.00 | Window Closed / Lapsed |