US3775761A - Fire detecting system with spurious signal rejection - Google Patents

Fire detecting system with spurious signal rejection Download PDF

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Publication number
US3775761A
US3775761A US00239633A US3775761DA US3775761A US 3775761 A US3775761 A US 3775761A US 00239633 A US00239633 A US 00239633A US 3775761D A US3775761D A US 3775761DA US 3775761 A US3775761 A US 3775761A
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United States
Prior art keywords
voltage
detectors
conductors
fire
alarm
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Expired - Lifetime
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US00239633A
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English (en)
Inventor
A Kobayashi
A Yokota
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Nittan Co Ltd
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Nittan Co Ltd
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/185—Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B25/00—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems
    • G08B25/01—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems characterised by the transmission medium
    • G08B25/04—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems characterised by the transmission medium using a single signalling line, e.g. in a closed loop

Definitions

  • ABSTRACT I A fire detecting system having a plurality of fire detec- [30] Foreign Application Priority Data tors connected across conductors for applying a volt- AprxlS, 1971 Japan .Q 46/23446 age thereto The detecwrs each include Switching 1 means which is closed upon operation of a detectorv 52 us. c1. 340/228 R, 340/411, 307/117, and Opened "P reduction of thevolmge on the 7 5 M ductors below a predetermined value. Voltage is sup- [51] Int. Cl. .I G08b 17/06 plied to the by means which responds to [58] Field of Search
  • This invention relates to a tire detecting system hav-
  • Some of the fire detecting systems whichhave been widely used include fire detectorseach having a controlled switch, such as a silicon controlled rectifier (hereinafter referred to as SCRU, which is closed in response to actuation of the fire sensing; means but is not opened again'unless the voltagethereacro ssis reduced below'a specific value; such detectors are advantageous in that the alarm is continuous eventhough the fire maybe sensedzfor a short time, but they also have an attendant disadvantage in that a; continuous alarm is provided when the detectoris actuated erroneously by amomentarily inducedvoltage, a short pass of (Smoke thrsus i dt t r' SPsiQs QsHSW wind, or any other cause otherthan fire. uch an erroneous alarm often cai ses substantial confusion and,
  • the fire detecting system in this invention includes a plurality offire detectors connected in parallel betweena pair of conductors and a e entral unit connectedto one end :of saidconduc'tors and eachof the detectors have a normally open switch which is connected between said conductors and closed in response to detectionoffire to short both the conductors.
  • the central unit includes a dc.
  • FIG. 1 is a schematic circuit diagram of one embodiment of a system in accordance wi th this invention
  • iwFlG. 2 is a simplified circuit diagram of the voltage stabilizing circuitof FIG. 1
  • I "FIGS. 3 and 4 are waveform diagrams which will aid in understanding the operation of the system of FIG. 1.
  • the tire detecting system accordingly thi invention includes a central unit 1 having a a o oi .7 detectors 2-11, 2- 2, connected in parallel between put terminals land 4, and a plurality of tire a pair of conductors 3 0and extending from the output terminals Sand
  • the fire detector 2 includes a fire sensor whichsenses a product of fire, such as smoke or temper ure, to produce an output and a normally open switehesnch an SCR 26, is closed by'the output of thefsensor to short the conductors 30 anddt) and is never restored to its non-conductive state unless the voltage qthereacross Y -is reduced below a specific va ue, 7
  • Thecentral unit comprises a power source section 5,
  • the po er source section ,5 includes a dc. voltage source rolsucn abattery and a normally closed pushbptton switch 11 connected in series with the voltage I source and used for restoration of the system when actuated.
  • f i v it e multivibrator section ,6 includes resistors 12, 13, .14 and ]1; 5;capacitors .16 and 17, NPN transistors 18 and 19 and diodes 20and The collector of transistor is'connected through the resistor 12 to the positive terminalof the power source, the emitter is connected to thenegative terminal of the power source and the negative output terminal 4 of the central unit 1, and thef bagseis connected to the cathode electrode .of the diode 2l which has its anode electrode connected through thieresistor 14 to the positiveterminal ofthepower'source.
  • Ihetransistor 19 has its collector connecte to thepositive terminal of the power source throughthe resistor 15, its emitter connected to the anod felectrodeof diode 2 3, and its base connected to 1 Yr; thjode electrode of the diode 20 which has its anodefelec'trode connected through the resistor 13 to the positive terminal of the power source.
  • the capaciis'ieonnectedbetween the junction A of the resistor l 2andt' he transistor 18'and the junction B of the resistor :"13 and the diode 2 0,and the capacitor 17 is between the junction C of the resistor 14 and the diode 21 and the junction D of the resistor 15 transistor 19-
  • the base electrode of the transistor also connected through a resistor 22 to the negative terminal of the power source and the base electrode of thetransisltor 19 is also connected to the cathode electrode of Zener diode 24 which has its ode connected to the negative terminal.
  • an deelectrodeofthe diode 23 is connected to K ve outputterrninal 3 of the central unit.
  • the I or l 9 and the diodes 23 and 24 enclosed by brokenhnesi) constitute a known stabilized voltage source for the fire detectors cooperation with the power source section 5 and is shown more clearly in FIG. 2.
  • the integrating circuit section 7 includes Zener diodes 27 and 31; capacitors 28 and 32 and a resistor 29.
  • the Zen er diode 27 has its cathode connected to the positive terminal of the power source and its anode to thejunction l).
  • the alarm section 8 includes a PNP transistor 33 having a base electrode connected to the cathode electrode of the Zener diode 31, an emitter electrode connected to the positive terminal of the power source and a collector electrode connected through a series connection of resistors 35 and 36 to the negative terminal of the source.
  • An NPN transistor 37 has a base electrode connected to the junction between the resistors 35. and 36, a collector electrode connected through a parallel connection of a relay unit 41' and an audible alarm 42 to the positive terminal of the source, and an emitter electrode connected directly to the negative terminal thereof.
  • This section further includes a resistor 34 connected between the emitter and base electrodes of the transistor 33 and a resistor 38 connected voltage is supplied from the voltage source 10 through the voltage stabilizing circuit 9 included in the multivibrator section 6 to the respective fire detectors 2-1, 2-2, connected in parallel between the conductors 30 and 40.
  • the voltage stabilizing circuit 9 which is schematically shown in FIG. 2 is of a type well-known in the art and therefore further description is not deemed necessary.
  • the emitter electrode of the transistor 18 is directly connected to the negative terminal of the source, a current flows through the resistor 14 and the diode 21 into the base electrode of the transistor 18 and keeps the transistor 18 in the ON condition. Accordingly, currents flow through the resistors 12 and 14 respectively.
  • the capacitor 16 is charged up to the Zener voltage of the Zener diode 24, making the junction B positive, and the capacitor 16 is charged up to the source voltage, making the junction D positive.
  • the emitter electrode of the transistor 19 is shorted through the SCR 26 to the negative terminal of the source 10,
  • the transistor 29 is driven into the ON state and the positive terminal of the charged capacitor 17 is connected to the negative terminal of the source 10. Consequently, the potential at the base electrode of the transistor 18 which is connected to the negative terminal of the capacitor 17 through the diode 21 is momentarily lowered to the potential of the emitter. Therefore, the transistor 18 is driven into the OFF state and exhibits a high impedance.
  • junctions A and C become positive.
  • the transistor 18 is driven again into the ON state and exhibits a low impedance. Therefore, the positive terminal A of the charged capacitor 16 is lowered to the negative terminal potential and, consequently, the base potential of the transistor 19 is also lowered momentarily to the potential of the emitter. Thus, the transistor 19 is driven again into the OFF state and exhibits a high impedance.
  • the voltage across the Zener diode 24 is also reduced to about zero volts and, therefore, the output voltage applied between the conductors 30 and 40 is similarly reduced to restore the actuated SCR 26 of the fire detector concerned to its original open state. Thus, the system is restored to its original condition.
  • the same operation is repeated until the cause of actuation is removed. Every cycle of such operation, detected by the voltage across the resistor 15 which is produced in response to conduction of the transistor 19 is accumulated successively in the capacitor 28 with a delay determined by the resistor 29 and the capacitor 28 and, every time the voltage across the capacitor 28 exceeds the Zener voltage of the Zener diode 31, it is transferred to and accumulated in the capacitor 32.
  • the Zener diode 27 connected across the resistor 15 serves the function of a voltage limiter to pass a voltage higher than its Zener voltage but to block undesirable low voltages.
  • FIG. 3 represents the voltage waveform appearing across the resistor 15.
  • voltages V V and V are the voltages for restoring the detector
  • the pushbutton switch 11 in the power source section 5 is pushed to interrupt the source voltage supply for a moment.
  • the system of this invention can distinguish the cause of actuation of the detector and give an alarm only when an actual fire occurs.
  • a fire detecting system comprising a plurality of fire detectors connected in parallel between a pair of conductors, a central unit connected to one end of said conductors, each of said detectors having a normally open switch connected between said conductors, said normally open switch being closed in response to actuation of said detectors and restored only by the reduc- 2.
  • said first means includes a multivibrator having stable and unstable states and initiating operation in response to closure of said switch, and a circuit connection for supplying said operating voltage to said detectors through a path in said multivibrator which is conductive during said stable state but nonconductive during said unstable state.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Fire Alarms (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)
  • Emergency Alarm Devices (AREA)
US00239633A 1971-04-15 1972-03-30 Fire detecting system with spurious signal rejection Expired - Lifetime US3775761A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP46023446A JPS5136119B1 (enrdf_load_stackoverflow) 1971-04-15 1971-04-15

Publications (1)

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US3775761A true US3775761A (en) 1973-11-27

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ID=12110715

Family Applications (1)

Application Number Title Priority Date Filing Date
US00239633A Expired - Lifetime US3775761A (en) 1971-04-15 1972-03-30 Fire detecting system with spurious signal rejection

Country Status (9)

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US (1) US3775761A (enrdf_load_stackoverflow)
JP (1) JPS5136119B1 (enrdf_load_stackoverflow)
AU (1) AU452761B2 (enrdf_load_stackoverflow)
CA (1) CA948290A (enrdf_load_stackoverflow)
CH (1) CH554031A (enrdf_load_stackoverflow)
FR (1) FR2133747B1 (enrdf_load_stackoverflow)
GB (1) GB1332270A (enrdf_load_stackoverflow)
IT (1) IT954665B (enrdf_load_stackoverflow)
ZA (1) ZA721943B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4102194A (en) * 1976-09-20 1978-07-25 Dickey-John Corporation Electronic bin temperature monitor
US4287515A (en) * 1979-04-27 1981-09-01 Baker Industries, Inc. Fire detection system with multiple output signals
US4814748A (en) * 1987-11-09 1989-03-21 Southwest Laboratories, Inc. Temporary desensitization technique for smoke alarms
US4916432A (en) * 1987-10-21 1990-04-10 Pittway Corporation Smoke and fire detection system communication

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52116920A (en) * 1976-03-27 1977-09-30 Taisei Corp Method of preventing sedimentation of sludge in underground petroleum storing tanks and apparatus therefor
JPS5471710U (enrdf_load_stackoverflow) * 1977-10-31 1979-05-22
JPS62229394A (ja) * 1986-03-14 1987-10-08 ニツタン株式会社 異常警報装置

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2903682A (en) * 1955-12-28 1959-09-08 Petcar Res Corp Flame detector system
US3147464A (en) * 1961-10-16 1964-09-01 Warren L Spielman First-out annunclator having input and supply control of indicator switching means
US3503067A (en) * 1964-09-29 1970-03-24 Etablis Pour Applic Electroniq Remote identification system
US3621262A (en) * 1968-02-15 1971-11-16 Francais Detection Eletr Alarm device gas discharge tube
US3694670A (en) * 1971-10-26 1972-09-26 Joseph M Marzolf Easily switched silicon controlled rectifier
US3719836A (en) * 1971-06-23 1973-03-06 C Possell Pressure sensitive sensor and control unit and method of using same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2903682A (en) * 1955-12-28 1959-09-08 Petcar Res Corp Flame detector system
US3147464A (en) * 1961-10-16 1964-09-01 Warren L Spielman First-out annunclator having input and supply control of indicator switching means
US3503067A (en) * 1964-09-29 1970-03-24 Etablis Pour Applic Electroniq Remote identification system
US3621262A (en) * 1968-02-15 1971-11-16 Francais Detection Eletr Alarm device gas discharge tube
US3719836A (en) * 1971-06-23 1973-03-06 C Possell Pressure sensitive sensor and control unit and method of using same
US3694670A (en) * 1971-10-26 1972-09-26 Joseph M Marzolf Easily switched silicon controlled rectifier

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4102194A (en) * 1976-09-20 1978-07-25 Dickey-John Corporation Electronic bin temperature monitor
US4287515A (en) * 1979-04-27 1981-09-01 Baker Industries, Inc. Fire detection system with multiple output signals
US4916432A (en) * 1987-10-21 1990-04-10 Pittway Corporation Smoke and fire detection system communication
US4814748A (en) * 1987-11-09 1989-03-21 Southwest Laboratories, Inc. Temporary desensitization technique for smoke alarms

Also Published As

Publication number Publication date
GB1332270A (en) 1973-10-03
CH554031A (de) 1974-09-13
CA948290A (en) 1974-05-28
AU4079072A (en) 1973-11-01
IT954665B (it) 1973-09-15
JPS5136119B1 (enrdf_load_stackoverflow) 1976-10-06
AU452761B2 (en) 1974-08-23
FR2133747A1 (enrdf_load_stackoverflow) 1972-12-01
DE2218198A1 (de) 1972-10-26
FR2133747B1 (enrdf_load_stackoverflow) 1973-07-13
ZA721943B (en) 1972-12-27
DE2218198B2 (de) 1973-05-10

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