US3717862A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fire detecting system and testing means therefor
Assignee: Nittan Co Ltd
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Filing: 1970-10-09
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Granted: 1973-02-20
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Expires: 1990-10-09
Abstract
Abstract A fire detecting system embodying a plurality of ionization smoke detectors and a receiving unit for supplying electrical energy to the smoke detectors, for sounding an alarm in the event a detector is actuated and for applying predetermined voltages to the detectors to test both operability and sensitivity.
Inventors
- 👤 K Sasaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:32
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
197 words
A fire detecting system comprising a pair of conductors, a plurality of ionization detectors each having a closed ionization chamber and an open ionization chamber connected in series across said conductors and a circuit including a field effect transistor connected to said chambers to detect an impedance change upon the entrance of smoke in said open chamber, a receiving unit including a voltage supply connected to said conductors and a relay connected in series with one of said conductors, a third conductor extending from said receiving unit, each of said circuits being connected between one of said pairs of conductors and said third conductor, means in said receiving unit including an impedance and switch for selectively interconnecting the other of said pair of conductors and said third conductor directly and through said impedance, and means for indicating the voltage drop across said impedance, each of said circuits upon being actuated by its associated ionization chamber produces an increase in current in said conductors to actuate said relay, said indicating means indicating the number of detectors that have been actuated upon the insertion of said impedance between said third conductor and the other of said pair of conductors.
Claim 2
Dependent Claim
197 words
A fire detecting system comprising a pair of conductors, a plurality of ionization detectors each having a closed ionization chamber and an open ionization chamber connected in series across said conductors and a circuit including a field effect transistor connected to said chambers to detect an impedance change upon the entrance of smoke in said open chamber, a receiving unit including a voltage supply connected to said conductors and a relay connected in series with one of said conductors, a third conductor extending from said receiving unit, each of said circuits being connected between one of said pairs of conductors and said third conductor, means in said receiving unit including an impedance and switch for selectively interconnecting the other of said pair of conductors and said third conductor directly and through said impedance, and means for indicating the voltage drop across said impedance, each of said circuits upon being actuated by its associated ionization chamber produces an increase in current in said conductors to actuate said relay, said indicating means indicating the number of detectors that have been actuated upon the insertion of said impedance between said third conductor and the other of said pair of conductors.
Claim 3
Dependent Claim
197 words
A fire detecting system comprising a pair of conductors, a plurality of ionization detectors each having a closed ionization chamber and an open ionization chamber connected in series across said conductors and a circuit including a field effect transistor connected to said chambers to detect an impedance change upon the entrance of smoke in said open chamber, a receiving unit including a voltage supply connected to said conductors and a relay connected in series with one of said conductors, a third conductor extending from said receiving unit, each of said circuits being connected between one of said pairs of conductors and said third conductor, means in said receiving unit including an impedance and switch for selectively interconnecting the other of said pair of conductors and said third conductor directly and through said impedance, and means for indicating the voltage drop across said impedance, each of said circuits upon being actuated by its associated ionization chamber produces an increase in current in said conductors to actuate said relay, said indicating means indicating the number of detectors that have been actuated upon the insertion of said impedance between said third conductor and the other of said pair of conductors.
Claim 4
Dependent Claim
197 words
A fire detecting system comprising a pair of conductors, a plurality of ionization detectors each having a closed ionization chamber and an open ionization chamber connected in series across said conductors and a circuit including a field effect transistor connected to said chambers to detect an impedance change upon the entrance of smoke in said open chamber, a receiving unit including a voltage supply connected to said conductors and a relay connected in series with one of said conductors, a third conductor extending from said receiving unit, each of said circuits being connected between one of said pairs of conductors and said third conductor, means in said receiving unit including an impedance and switch for selectively interconnecting the other of said pair of conductors and said third conductor directly and through said impedance, and means for indicating the voltage drop across said impedance, each of said circuits upon being actuated by its associated ionization chamber produces an increase in current in said conductors to actuate said relay, said indicating means indicating the number of detectors that have been actuated upon the insertion of said impedance between said third conductor and the other of said pair of conductors.
Claim 5
Dependent Claim
14 words
A fire detecting system according to claim 1 wherein said impedance is a resistor.
Claim 6
Dependent Claim
68 words
A fire detecting system according to claim 2 wherein each of said circuits includes switching means interconnected with said transistor and actuated thereby, said switching means being connected between said one of said pair of conductors and said third conductor, and a resistor connected between the side of said switching means connected to said one of said pair of conductors and the other of said pair of conductors.
References Cited (Backward Citations)
US3500368A
Cited
US3564524A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-20 | 1976-08-21 | 1977-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-20 | 1980-08-21 | 1981-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-20 | 1984-08-21 | 1985-02-20 | $7700.00 | Window Closed / Lapsed |