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US3676877A
Expired / Lapsed
US
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Fire alarm system with fire zone locator using zener diode voltage monitoring
Assignee: MITTAN CO Ltd
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Filing: 1971-04-07
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Granted: 1972-07-11
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Expires: 1991-04-07
Abstract
Abstract A fire alarm system having a plurality of detectors operably to actuate a single receiver to sound an alarm upon the presence of fire, said detectors each having a zener diode interposed in the conduction path so that at least part of the current flows through the zener diode, each zener diode having a voltage differing from the zener diodes of the other detectors and said receiver including means sensing the specific zener diode voltage of an actuated detector in order to determine the detector that has been actuated.
Inventors
- 👤 Tetsuo Kobayashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:00
CPC Classifications
G; G08; G08B; G08B25/00; G08B25/01; G08B25/018; G08B17/00
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
115 words
A fire alarm system, comprising a plurality of detecting units for sensing a fire and generating an electric signal and a receiving unit for receiving said electric signal and producing an alarm, each of said detecting units having a conduction path including a normally open switch which is closed when a fire is sensed, each of said detecting units including a zener diode connected in conjunction with said conduction path so that at least a part of conduction current of said switch flows through said zener diode, said receiving unit including means for indicating a voltage across said zener diode, and said zener diode having a zener voltage peculiar to each of said detecting units.
Claim 2
Dependent Claim
115 words
A fire alarm system, comprising a plurality of detecting units for sensing a fire and generating an electric signal and a receiving unit for receiving said electric signal and producing an alarm, each of said detecting units having a conduction path including a normally open switch which is closed when a fire is sensed, each of said detecting units including a zener diode connected in conjunction with said conduction path so that at least a part of conduction current of said switch flows through said zener diode, said receiving unit including means for indicating a voltage across said zener diode, and said zener diode having a zener voltage peculiar to each of said detecting units.
Claim 3
Dependent Claim
41 words
A fire alarm system according to claim 1 wherein said conduction path includes said zener diode connected in series with said normally open switch and said conduction path of each detecting unit is connected in common across said voltage indicating means.
Claim 4
Dependent Claim
78 words
A fire alarm system according to claim 1 wherein said conduction path includes a second zener diode connected in series with said first zener diode and said normally open switch, said first zener diode of each detecting unit being connected in common across said voltage indicating means through a diode included in said detecting unit, and the sum of the zener voltages of said first and second zener diodes is selected to be equal throughout the detecting units.
Claim 5
Dependent Claim
59 words
A fire alarm system according to claim 1 wherein said conduction path includes a diode connected in series with said normally open switch, said zener diode being connected to the junction between said diode and said switch and the series connection of said zener diode and said switch of each detecting unit being connected across sAid voltage indicating means.
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) | 1975-07-11 | 1976-01-10 | 1976-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-11 | 1980-01-10 | 1980-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-11 | 1984-01-10 | 1984-07-11 | $7700.00 | Window Closed / Lapsed |