US3778796A - Fire alarming system - Google Patents

Fire alarming system Download PDF

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Publication number
US3778796A
US3778796A US00120178A US3778796DA US3778796A US 3778796 A US3778796 A US 3778796A US 00120178 A US00120178 A US 00120178A US 3778796D A US3778796D A US 3778796DA US 3778796 A US3778796 A US 3778796A
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United States
Prior art keywords
conductors
detector
fire
alarm
receiver
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00120178A
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English (en)
Inventor
Y Honda
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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
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • 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

  • a fire alarm system having a plurality of detectors ar. 1,1 7 Japan 45/268 2 connected to a pair of conductors, a receiver and a power supply connected to said conductors and an if alarm connected to the power supply and said conduci S 184 tors so that an alarm is sounded upon activation of a l l 0 6 detector, each detector upon activation producing a preselected AC signal for transmission to the receiver 56 R f d and the receiver includes band pass filters activated by l 1 e erences e particular frequencies and having associated indicat- UNITED STATES PATENTS ing means so that the activated detector and therefore 3,160,866 12/1964 Meili 340/237 S UX the location of the fire or smoke can be immediately 3,530,450 9/1970 Walthard et al.
  • This invention relates to a fire alarm system and'more particularly to an alarm system including novel and improved means fordetecting the specific area in which fire has occurred.
  • one object of this invention is to provide a fire alarm system including a number of fire or smoke detectors connected in parallel on a single communication line and having novel and improved means for detecting and indicating the detector which is excited.
  • each of the detectors is provided with an oscillator which generates an AC signal having its own characteristic frequency when excited and the receiver includes means for detecting the frequency of the received signal and indicating the detector which has generated the signal. Therefore, the system of this invention can generate an alarm signal and at the same time indicate the detector being excited.
  • FIG. 1 is a block diagram representing a general configuration of the fire alarm system according to this invention
  • FIG. 2 is a circuit diagram representing an embodiment of the detector used in the system of this invention.
  • FIG. 3 is a circuit diagram representing another embodiment of the detector used in the system of this invention.
  • FIG. 4 is a circuit diagram representing an embodiment of the receiver used in the system of this invention.
  • FIG. 5 is a circuit diagram representing a modification of the detector shown in FIG. 3;
  • FIG. 6 is a circuit diagram representing a part of a further embodiment of the detector used in the system of this invention.
  • FIG. 7 is a circuit diagram representing a modification of apart of the detector shown in FIG. 2;
  • FIG. 8 is a circuit diagram representing a modifica tion of the-circuit shown in FIG. 5;
  • FIG. 9 is a circuit diagram representing a modification of the circuit shown in FIG. 6.
  • FIG. 1 there shown is a general configuration of the fire alarm system wherein a number of fire or smoke detectors 3-1, 3-2, 3-3, 3-n are connected in parallel between a pair of conductors l and 2 which are in turn connected to a receiver 4.
  • the each detector 3 includes a normally open switch circuit (not shown) which is closed when the detector senses heat or smoke, and the receiver 4 includes a power supply and an alarm device (not shown) connected in series between the conductors land 2. Therefore, when the switch circuit in the detector is closed, the alarm circuit is energized to give an alarm, as in the case of prior systems.
  • each detector also includes means for generating an AC signal having a predetermined characteristic frequency, and sending it to the receiver through the conductors l and 2, when the detector is excited or the switch circuit is closed, and the receiver 4 also includes a number of bandpass filters corresponding to the respective characteristic frequencies of the detectors and corresponding indicators, such as lamps, which are energized respectively by the signals passing the respective filters connected thereto. Therefore, if one of the detectors senses heat or smoke, an AC signal having a characteristic frequency of said detector is sent to the receiver and this signal passes one of the filters in the receiver which has a corresponding pass-band and energizes the indicating lamp associated with said detector.
  • FIG. 2 representing an embodiment of this invention using a bimetallic fire detector 3
  • three resistors 23, 24, and 25 are connected in series between a pair of conductors l and 2 which are connected to the receiver 4 (FIG. 1) and to which a predetermined voltage is applied from the power supply in the receiver.
  • a normally open switch 22 is connected in parallel with the resistor 24.
  • the switch 22 is interlocked with a bimetallic heat sensing element 21 so that it is closed when the element 21 senses a predetermined temperature.
  • the resistor 24 is short-circuited by the switch 22 and a current which is enough to energize the alarm device in the receiver 4 is caused to flow through the conductors l and 2.
  • the junction of the resistors 24 and 25 is connected through a capacitor '53 to one end of the primary winding of a transformer 52 the other end of which is connected to the base electrode of a transistor 51.
  • One end of the secondary winding of the transformer 52 is connected through a capacitor 54 to the second conductor 2 and also through a resistor 56 to the first conductor 1, and the other end of the transformer 52 is connected through the collector-emitter path of the transistor 51 to the ground.
  • the second conductor 2 is also grounded as shown in the drawing.
  • the transistor 51, transformer 52 and capacitor 53 and 54 and resistors 55 and 56 which are surrounded by a dashed square 5 constitute a blocking oscillator having a characteristic frequency determined by the values of these elements.
  • the heat sensing element 21 senses heat and closes the switch 22
  • the biasing voltage of the transistor 51 is changed to drive the oscillator 5 into oscillation at its own characteristic frequency.
  • the AC signal of this frequency is sent through the capacitor 54 and the resistor 56 to the receiver 4 and sensed in the manner to be described.
  • the ionization smoke detector 6 includes a closed ionization chamber 61 having a pair of electrodes 611 and 612 and a radioactive source 613 and closed to the external air, an open ionization chamber 62 having a similar pair of electrodes 621 and 622 and a radioactive source 623 and opened to the external air so as to allow smoke to come in and a field effect transistor 63.
  • the ionization chambers are connected in series between the pair of conductors 1 and 2 and the junction between the both chambers is connected to the gate electrode of the field effect transistor 63.
  • the source-drain conduction path of the field effect transistor 63 which includes a load resistor 64 is also connected between the pair of conductors l and 2.
  • the source electrode of the field effect transistor 63 is connected through a zener diode 65 to the control electrode of a silicon controlled rectifier (SCR) 66 whose conduction path is connected through a potentiometer 67 between the conductors l and 2.
  • SCR silicon controlled rectifier
  • the impedance of that chamber is varied and thereby changes the gate potential of the field effect transistor 63. This results in increase of the drain-tosource current of the field effect transistor and accordingly in an increase of the source potential of the transistor.
  • the potential exceeds the zener voltage of the zener diode 65, it is applied to the control electrode of the SCR 66 and drives it into conduction. Therefore, the conductors 1 and 2 are short-circuited through the SCR 66 to energize the alarm device in the receiver 4.
  • the oscillator portion 7 consists of a tuning fork oscillator circuit including a diode 71, a tuning fork 72, capacitors 73 and 74, resistors 75, 76, and 77 and a transistor 78.
  • a tuning fork oscillator circuit including a diode 71, a tuning fork 72, capacitors 73 and 74, resistors 75, 76, and 77 and a transistor 78.
  • one leg of the tuning fork 72 is connected through a piezoelectric element attached thereto and through a diode 71 to the movable contact of the potentiometer 67 and the other leg of the tuning form 72 is connected through another piezoelectric element attached thereto and to the base electrode of the transistor 78.
  • the tuning fork itself is connected directly to the second conductor 2 and the base electrode of the transistor 78 is connected through a parallel connection of the capacitor 73 and the resistor 75 to the conductor 2.
  • the base electrode also is connected through the resistor 76 to the collector electrode of the same transistor 78 and to the anode electrode of the diode 71.
  • the emitter electrode of the transistor 78 is connected through a parallel connection of the capacitor 74 and the resistor 77 to the conductor 2.
  • This oscillator circuit has a characteristic frequency determined by the mechanical characteristics of the tuning fork 72 and the electrical values of the other elements.
  • the biasing voltage of the oscillator circuit at the movable contact of the potentiometer 67 changes and the oscillator circult is driven into oscillation when the biasing condition is fulfilled.
  • This AC signal having its own characteristic frequency is amplified by a resonance circuit consisting of a capacitor 25 and the primary winding of a transformer 26 and the signal induced into the secondary winding of the transformer 26 is transmitted to the receiver 4.
  • Capacitors 27 and 28 are inserted for blocking the DC component.
  • the receiver 4 includes an alarm device shown in a dashed block 8 and consists of an electromagnetic relay 8] having a normally open contact, a power supply 82 and a parallel connection of an indication lamp 83 and a sound generator 84 connected in series with the relay contact and the power supply.
  • One terminal of the coil of the relay 81 is connected to the first conductor 1 and the other terminal is connected through a low-pass filter consisting of capacitors 11 and 12 and a choke coil 13, surrounded by a dashed square 10, to a voltage source 45.
  • the receiver 4 also includes a high-pass filter 9 consisting of capacitors 91 and 92 and a choke coil 93 and having the input connected to the conductors l and 2 and the output connected through an amplifier 14 to a frequency discriminating network 40.
  • the frequency discriminating network 40 consists of a number of discriminating channels respectively corresponding to the detectors 3-1, 3-2, 3-3, 3-n (FIG. 1). For purposes of simplification, only three channels are shown in the drawing. Moreover, for the purpose of explanation, it is assumed that the first, second, and third channels, respectively, correspond to the detectors 3-1, 3-2, and 3-3 and the detectors 3-1, 3-2, and 3-3 include oscillator circuits having characteristic frequencies of f,, f and f respectively.
  • Each frequency discriminating channel consists of a bandpass filter 41, an amplifier 42, a rectifier 43 and an indicator 44.
  • the passfrequencies of the filters 41-1, 41-2, and 41-3 of the first, second and third channels are previously selected to be f f and f respectively.
  • the DC component of the signal generated by the detector passes the low-pass filter 10 and energizes the alarm device 8 and at the same time the AC component of the signal having the characteristic frequency passes the high pass filter 9, is being amplified by the amplifier 14, and is fed to the frequency discriminating network 40.
  • the output of the amplifier 14 only passes the bandpass filter 41-1, having the passfrequency f, and is amplified by the amplifier 42-1, rectified by the rectifier 43-1 and indicated by the indicator 44-1 such as an indicating lamp. Since the other bandpass filters 41-2 and 41-3 do not pass the frequency f, the signal is only processed in the first channel and indicates that the detector 3-1 has sensed the fire.
  • the alarm device 8 when any of the detectors senses a fire, the alarm device 8 is activated and the detector is indicated by the indicator 44 of the frequency discriminating network 40. This is also true even when a plurality of detectors are excited simultaneously.
  • FIGS. 5 and 6 represent two examples thereof.
  • an AC source 30 having a characteristic frequency is connected to the primary winding of a transformer 31, the secondary winding of which is connected in series with the conduction path of the SCR 66 of the ionization type smoke detector 6 shown in FIG. 3.
  • a DC conduction loop including the alarm device 8 is completed and at the same time a signal from the AC source 30 is coupled through the transformer 31 to the loop and superimposed on the DC component to be sent over the conductors 1 and 2.
  • Both AC and DC components are processed in the same manner described in conjunction with the circuit of FIG. 4.
  • an AC source 30 which is always in oscillatory condition as in the case of the AC source 30 in FIG. 5, is coupled through a transformer 31 to a closed circuit consisting of the secondary winding of the transformer 31, the primary winding of a transformer 32 and a pair of oppositely poled diodes 33 and 34.
  • the secondary winding of the transformer 32 is connected through DC blocking capacitors 35 and 36 to the conductors 2 and 1, respectively.
  • the center tap of the secondary winding of the transformer 31 is connected through a normally open switch 37 to the second conductor 2 and the center tap of the primary winding of the transformer 32 is directly connected to the first conductor 1.
  • the normally open switch 37 corresponds to the switch 22 of FIG. 2 or the SCR 66 of FIG.
  • FIGS. 7, 8, and 9 represent modifications of the circuits of FIGS. '2, 5, and 6 which are provided with speakers.
  • the transformer 52 is provided with the tertiary winding 57 and the speaker 58 is arranged to be driven by the tertiary winding 57.
  • a transformer 59 is connected in series with the conduction path of the SCR 66 and the speaker 58 is arranged to be driven by the secondary winding of the transformer.
  • the speaker 58 is arranged to be driven by the tertiary winding of the transformer 32.
  • the site of a tire and area of the fire can be quickly determined at the receiver and specific fire fighting instructions can be issued immediately.
  • a fire alarm system comprising a plurality of fire detecting units for sensing heat or smoke, a receiving station including a direct current power supply, a pair of conductors connected at one end to said power supply, connections between each detecting unit and said conductors, each of said units including an AC generating device having a preselected frequency, heat or smoke detecting means electrically coupled with said generating means and with said conductors, and means including DC blocking means coupling said generator to said conductors whereby actuation of one of said detecting means at least partially shunts said conductors to increase the flow of current therethrough and causes an AC signal to be applied to said conductors, and said receiving means includes r'neans responsive to an increase in current in said conductors to produce an alarm, frequency discriminating means responsive to said AC signals and a plurality of indicating means interconnected with said discriminating means, each of said indicating means being selectively activated by said discriminating means upon activation of one of said detecting units to identify the location of the detecting unit producing an alarm.

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  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Fire Alarms (AREA)
  • Fire-Detection Mechanisms (AREA)
US00120178A 1970-03-31 1971-03-02 Fire alarming system Expired - Lifetime US3778796A (en)

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Application Number Priority Date Filing Date Title
JP2684270 1970-03-31

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US3778796A true US3778796A (en) 1973-12-11

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US (1) US3778796A (OSRAM)
CA (1) CA939778A (OSRAM)
DE (1) DE2115759B2 (OSRAM)
FR (1) FR2083678B1 (OSRAM)
GB (1) GB1320651A (OSRAM)
ZA (1) ZA71780B (OSRAM)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3946374A (en) * 1970-08-13 1976-03-23 Sci Systems, Inc. Rate-of-change combustion and contamination detection device
US3952294A (en) * 1973-03-19 1976-04-20 General Time Corporation Smoke detection alarm system
US4287515A (en) * 1979-04-27 1981-09-01 Baker Industries, Inc. Fire detection system with multiple output signals
US4435698A (en) 1980-06-11 1984-03-06 Hekatron Gmbh Circuit arrangement for the transmission of measurements to a central, especially in a fire alarm system
EP0093095A3 (en) * 1982-04-23 1986-12-30 Cerberus Ag A method and an apparatus for identifying a detector giving an alarm in a loop circuit having a predetermined number of detectors connected in parallel
EP0362985A1 (en) * 1988-09-05 1990-04-11 Apollo Fire Detectors Limited Improved address setting means for fire detectors
US5889468A (en) * 1997-11-10 1999-03-30 Banga; William Robert Extra security smoke alarm system
US20090251322A1 (en) * 2006-02-24 2009-10-08 Airbus France Fire detection system and aircraft equipped with such a system
US20090322526A1 (en) * 2008-06-25 2009-12-31 Lontka Karen D Arrangement and method for communicating with notification appliances
US20250037560A1 (en) * 2021-11-26 2025-01-30 Dryad Networks GmbH Forest fire early detection system with piezo/bimetallic sensor, and method for operating a forest fire early detection system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2321747B (en) * 1997-01-30 2000-10-18 Rafiki Protection Limited Alarm system

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2607220A (en) * 1947-04-14 1952-08-19 Philip W Martin Means for measuring conditions in deep wells
US2662933A (en) * 1951-04-26 1953-12-15 Bell Telephone Labor Inc Multiplex carrier telegraph system
US3160866A (en) * 1957-02-19 1964-12-08 Cerberus G M B H Electric alarm system
US3357009A (en) * 1964-12-14 1967-12-05 Miller Peter Condition-responsive system for impressing distinctive frequency alarm tone on transmission line
US3388389A (en) * 1964-06-09 1968-06-11 Davis Foreman Alarm systems
US3484775A (en) * 1965-10-20 1969-12-16 Wallace Dean Cline Theft prevention system
US3530450A (en) * 1966-05-09 1970-09-22 Cerberus Ag Fire alarm systems with monitoring device for fire alarms connected in groups to a central station

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR983536A (fr) * 1949-02-03 1951-06-25 Installation radio-électrique de sécurité

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2607220A (en) * 1947-04-14 1952-08-19 Philip W Martin Means for measuring conditions in deep wells
US2662933A (en) * 1951-04-26 1953-12-15 Bell Telephone Labor Inc Multiplex carrier telegraph system
US3160866A (en) * 1957-02-19 1964-12-08 Cerberus G M B H Electric alarm system
US3388389A (en) * 1964-06-09 1968-06-11 Davis Foreman Alarm systems
US3357009A (en) * 1964-12-14 1967-12-05 Miller Peter Condition-responsive system for impressing distinctive frequency alarm tone on transmission line
US3484775A (en) * 1965-10-20 1969-12-16 Wallace Dean Cline Theft prevention system
US3530450A (en) * 1966-05-09 1970-09-22 Cerberus Ag Fire alarm systems with monitoring device for fire alarms connected in groups to a central station

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3946374A (en) * 1970-08-13 1976-03-23 Sci Systems, Inc. Rate-of-change combustion and contamination detection device
US3952294A (en) * 1973-03-19 1976-04-20 General Time Corporation Smoke detection alarm system
US4287515A (en) * 1979-04-27 1981-09-01 Baker Industries, Inc. Fire detection system with multiple output signals
US4435698A (en) 1980-06-11 1984-03-06 Hekatron Gmbh Circuit arrangement for the transmission of measurements to a central, especially in a fire alarm system
EP0093095A3 (en) * 1982-04-23 1986-12-30 Cerberus Ag A method and an apparatus for identifying a detector giving an alarm in a loop circuit having a predetermined number of detectors connected in parallel
EP0362985A1 (en) * 1988-09-05 1990-04-11 Apollo Fire Detectors Limited Improved address setting means for fire detectors
USRE37255E1 (en) 1988-09-05 2001-07-03 Apollo Fire Detectors Limited Address setting means for fire detectors
US5889468A (en) * 1997-11-10 1999-03-30 Banga; William Robert Extra security smoke alarm system
US20090251322A1 (en) * 2006-02-24 2009-10-08 Airbus France Fire detection system and aircraft equipped with such a system
US8094030B2 (en) * 2006-02-24 2012-01-10 Airbus Operations Sas Fire detection system and aircraft equipped with such a system
US20090322526A1 (en) * 2008-06-25 2009-12-31 Lontka Karen D Arrangement and method for communicating with notification appliances
US20250037560A1 (en) * 2021-11-26 2025-01-30 Dryad Networks GmbH Forest fire early detection system with piezo/bimetallic sensor, and method for operating a forest fire early detection system

Also Published As

Publication number Publication date
FR2083678A1 (OSRAM) 1971-12-17
CA939778A (en) 1974-01-08
DE2115759B2 (de) 1973-02-01
ZA71780B (en) 1971-10-27
GB1320651A (en) 1973-06-20
DE2115759A1 (de) 1971-10-28
FR2083678B1 (OSRAM) 1974-10-31

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