US2847662A - Signalling system for automatic fire alarm installation - Google Patents

Signalling system for automatic fire alarm installation Download PDF

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Publication number
US2847662A
US2847662A US496880A US49688055A US2847662A US 2847662 A US2847662 A US 2847662A US 496880 A US496880 A US 496880A US 49688055 A US49688055 A US 49688055A US 2847662 A US2847662 A US 2847662A
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United States
Prior art keywords
relay
circuit
alarm
current
fire alarm
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Expired - Lifetime
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US496880A
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English (en)
Inventor
Lindgren Erik Gustaf
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
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Telefonaktiebolaget LM Ericsson AB
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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
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/06—Monitoring of the line circuits, e.g. signalling of line faults
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/06—Electric actuation of the alarm, e.g. using a thermally-operated switch

Definitions

  • the present invention relates to a signalling system for an automatic fire alarm installation.
  • signalling systems for fire alarm installations in which one or more two-wire circuit systems are continuously kept under current and normally open temperature responsive alarm switches bridge the two wires of the circuit systems. These alarm switches close their contacts in response to an excessive temperature caused by fire, thereby short-circuiting the two wires whereby an energizing circuit is closed for an alarm device.
  • One of the objects of the present invention is to provide a signalling system for fire alarm installations of the general kind above referred to, which discriminates between changes in the circuit system caused by a line fault and changes caused by closing of an alarm switch due to fire and which indicate the cause of the change in the circuit by different signals.
  • Such arrangement affords the advantage of eliminating the annoyance of a false fire alarm.
  • Another object of the invention is a signalling system the signals of which indicate the approximate location of the fire thereby expediting the required steps for extinguishing the fire.
  • Still another object of the invention is to provide a signalling system in which the total area to be supervised is divided in sectional areas each of which is individually supervised by the associated detecting and indicating means whereby the approximate location of a fire or another cause causing an excessive temperature can be more readily located.
  • Fig. 1 is a diagrammatic circuit system of the entire installation according to the invention
  • Fig. 2 shows a network modifying the detecting means of the installation
  • Fig. 3 shows another modification of the detecting network.
  • the signalling system and installation comprises a two-wire circuit system, the two wires or branches of which are designated by a and b, and a central control installation including four relays 1, 11, 12, 13 and four signalling lamps 14, 15, 16 and 17.
  • Relay 1 is a common control relay controlling contact arms 20, 8, 9, and 21. Relay 1 is shown energized and it is assumed that in accordance with the conventions used for the diagrammatic showing of relays and the contact arms thereof, the contact arms move into the direction away from the relay coil when the relay deenergizes, that is, contact arm 20 will move to the left and the other contact arms to the right. As is evident, the contact 2,847,662 Patented Aug.
  • the indicating means of the installation comprise a lamp 14 controlled by a relay 1 and lamps 15, 16 and 17 controlled by relays 11, 12 and 13 respectively.
  • each installation has its own control relay 1 but the indicating relays 11, 12 and 13 may be common to several circuit systems a and b, in which event they are connected to the several systems as shown for one system.
  • a direct current circuit is normally closed from the positive pole of a source of current through branch a, the coil of relay 1, branch b including relay contacts 2, 3, 4 and 5 connected in series and a resistance 6 to the negative pole. If there is a break in line branches a and b or a short-circuit between them, the flow of current through the coil of relay 1 is interrupted or at least decreased. As a result the relay releases and its contacts 2, 3, 4 and 5 are opened due to the movement of contact arms 8, 9, 10 and 21 to the right. Branch b is now divided into three sections each of which is connected through contact arms 8, 9 and 10 to supervisory relays 11, 12 and 13.
  • control relay 1 due to a break in the circuit will not close an energizing circuit for any of the supervisory relays as the circuit of each of the relay coils includes one of the alarm switches 7 which are still open.
  • signalling lamp 14 is closed due to a movement of contact arm 20 to the left as previously described. Ignition of lamp 14 indicates that there is a fault in the circuit.
  • FIGs. 2 and 3 show networks which eliminate the aforementioned rare but possible source of false alarm.
  • a current direction dependent impedance means 18 shown as a rectifier is connected in series with each of the alarm switches 7. If new the supervisory relays 11, 12, and 13 are connected to a source of current producing a polarity shifting direct current or an alternating current, release of control relay 1 due to deenergization by the closing of an alarm switch 7 willpermit fiow of'current in one direction only through the closed alarm switch and the respective supervisory relay. However, when current is supplied due to a direct short-circuit between theline branches a flow of current in-both directions will reach the respective supervisory relays.
  • the supervisoryrelays used in this arrangement are of the well-known kind which does not respond to current flowing in both directions, but to unidirectional current only. Consequently a direct short-circuit caused by a'fault rather than by a fire effecting closing of an alarm switch will be correctly indicated as a line fault by the closing of circuit of lamp 14 by relay 1.
  • a voltage dependent resistance19 is connected in series with each of the alarm switches 7.
  • Such resistance for instance a siliceous carbide resistance, decreases its resistance value as the voltage across the resistance increases.
  • a source of current supplies the supervisory circuit including relays 11, '12 and 13 with current of varying voltages, namely a normal voltage and a voltage higher than normal. If the current strengths, which in the event of a short-circuit reach a supervisory relay, are proportional to the voltages that occur through a short-circuit due to a line fault; the respective supervisory relay cannot respond due to its arrangement. However, when the relation between the current strengths is greater than the relation between the voltages which occur when alarm switch 7 is closed, the respective supervisory relay responds and closes the circuit of its signal lamp 15, 16 or 17.
  • a signalling system for an automatic fire alarm installation comprising, in combination, a closed two-wire energizing circuit means, a plurality of cross connections across the two wires each including a detecting temperature sensitive switch contact biased into the open position but closing in response to an ambient temperature above a predetermined value, a common control relay means having and controlling a plurality of pairs of relay contacts, the coil of said relay means and one contact of each pair being included in series in said two-wire circuit means, the said series contacts being closed in the energized state of said relay 0nd contact of a respective pair, and a plurality of indicating means each controlled by a respective one of said supervisory relay means whereby, upon deenergization of said control relay means only due to a fault in said twowire circuit means, said circuit means is separated in a plurality of networks by opening of said series contacts, each network including a respective supervisory relay means and at least one open detecting contact and whereby, upon.
  • said two-wire circuit means are separated in said several networks and the respective supervisory relay means is energized for actuating its signal means over said other contact of the respective pair of relay contacts.
  • said impedance means comprises a rectifying means.
  • each of said cross connections includes a voltage responsive impedance means, said supervisory relay means being arranged to be actuated only in response to a current strength caused by a voltage due to a closing of a detecting contact.
  • said impedance means comprises a resistance means having a characteristic decreasing the resistance value thereof in response to an increasing voltage.
  • said resistance means comprises a siliceous carbide resistor.

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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)
US496880A 1954-04-01 1955-03-25 Signalling system for automatic fire alarm installation Expired - Lifetime US2847662A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE333751X 1954-04-01

Publications (1)

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US2847662A true US2847662A (en) 1958-08-12

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ID=20308174

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Application Number Title Priority Date Filing Date
US496880A Expired - Lifetime US2847662A (en) 1954-04-01 1955-03-25 Signalling system for automatic fire alarm installation

Country Status (5)

Country Link
US (1) US2847662A (fr)
CH (1) CH333751A (fr)
DE (1) DE1022500B (fr)
FR (1) FR1121427A (fr)
GB (1) GB769249A (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3066487A (en) * 1958-05-12 1962-12-04 Bendix Corp Combustion starter having overspeed safety
US3083358A (en) * 1957-04-25 1963-03-26 Sound Diffusion Auto Thermatic Detecting and indicating apparatus, particularly for fire
US3144589A (en) * 1959-09-16 1964-08-11 Gen Electric Control system
US5532675A (en) * 1994-12-29 1996-07-02 Linda Johnson Alarm tester

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2308711A (en) * 1995-12-15 1997-07-02 Cga Direct Thatch temperature monitor

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1537211A (en) * 1922-09-07 1925-05-12 John H Wootton Signaling system
US2605342A (en) * 1948-12-10 1952-07-29 Sherman D Spurling Fire alarm system
US2695994A (en) * 1952-06-25 1954-11-30 Gen Sonics Corp Supervised signaling system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE748751C (de) * 1937-12-21 1944-11-09 Elektrische Alarmanlage mit einer oder mehreren UEberwachungsschleifen
DE956117C (de) * 1954-10-23 1957-01-10 Olaf Ingemar Harald Ekman Alarm- oder Kontrollanlage

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1537211A (en) * 1922-09-07 1925-05-12 John H Wootton Signaling system
US2605342A (en) * 1948-12-10 1952-07-29 Sherman D Spurling Fire alarm system
US2695994A (en) * 1952-06-25 1954-11-30 Gen Sonics Corp Supervised signaling system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3083358A (en) * 1957-04-25 1963-03-26 Sound Diffusion Auto Thermatic Detecting and indicating apparatus, particularly for fire
US3066487A (en) * 1958-05-12 1962-12-04 Bendix Corp Combustion starter having overspeed safety
US3144589A (en) * 1959-09-16 1964-08-11 Gen Electric Control system
US5532675A (en) * 1994-12-29 1996-07-02 Linda Johnson Alarm tester

Also Published As

Publication number Publication date
DE1022500B (de) 1958-01-09
CH333751A (de) 1958-10-31
GB769249A (en) 1957-03-06
FR1121427A (fr) 1956-08-14

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