US3603949A - Fire alarm installation - Google Patents

Fire alarm installation Download PDF

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Publication number
US3603949A
US3603949A US738046A US3603949DA US3603949A US 3603949 A US3603949 A US 3603949A US 738046 A US738046 A US 738046A US 3603949D A US3603949D A US 3603949DA US 3603949 A US3603949 A US 3603949A
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alarms
conductors
fire
central station
transistor
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US738046A
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English (en)
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Beat Walthard
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Cerberus AG
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Cerberus AG
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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
    • G08B29/12—Checking intermittently signalling or alarm systems
    • G08B29/14—Checking intermittently signalling or alarm systems checking the detection circuits
    • G08B29/145—Checking intermittently signalling or alarm systems checking the detection circuits of fire detection circuits
    • 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

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  • a fire alarm installation which provides positive detection of the response or nonresponse of an individual fire alarm during the normal operational condition izgg fiyg T k thereof as well as during a checking operation.
  • Each of the inrawmg dividual fire alan'ns are provided with circuits which exhibit a US.
  • Cl MAD/2M high impedance for supply voltages of a first polarity and a low 340/409 impedance for supply voltages of a second polarity during norlnt.
  • Cl GllBb 29/00 mal operational conditions; During; alarm conditions, howlField of Search 1. 340/214, ever, the impedance-polarity relationships reverse and such is 409 detected at a remote central station.
  • the present invention relates to an improved fire alarm installation of the type incorporating a plurality of two-conductor, parallely connected fire alarms operably coupled with a central signal station.
  • Fire alarm installations of the type wherein fire alarms are arranged together in groups and are parallely connected and coupled via only two conductors with a central station have proven to be particularly advantageous because of their low installation cost.
  • Known installations of this type are supplied with direct current.
  • the individual fire alarms during their normal state or condition, exhibit a high impedance and, during their alarm state or condition, exhibit a low impedance, whereby the current flowing through the groups of fire alarms during response ofone or a number of fire alarms is directly or indirectly utilized for triggering an alarm at the central station.
  • the criteria for triggering of the alarm at the central station is designated current in contrast to no current.
  • the invention is characterized by the features that the individual fire alarms are provided with circuits which, for the normal operational condition, provide a high impedance for supply voltages of a first polarity and provide a low impedance for supply voltages of a second polarity. In the case of an alarm, these impedances reverse. Furthermore, means are provided at the central station which deliver a voltage of alternating polarity to the supply conductor and, by carrying out impedance measurements, determine the following three operating conditions of the group of fire alarms:
  • At least one fire alarm is alarmed and at least one fire alarm is not alarmed (low impedance during both polarities of the supply voltage);
  • the circuits for the individual fire alarms which, as stated above, provide a high impedance for supply voltages of the first polarity and a low impedance for supply voltages of the second polarity during the normal operational condition and, in the case of an alarm reverse these impedances, consist of at least two parallely arranged current paths which, on the one hand, can be connected via a diode of different polarity with one supply conductor and, on the other hand, can be connected via a reversing or selector switch to the other supply conductor, whereby the reversing switch changes its position during response of a fire alarm.
  • FIG. 1 is a block diagram of the invention fire alarm installation
  • FIGS. 2a to 22 are diagrams which serve to explain the mode of operation of the inventive fire alarm installation
  • FIG. 3 is a first embodiment of a fire alarm suitable for use in conjunction with the inventive fire alarm installation
  • FIG. 5 is a third embodiment of a tire alarm designed in accordance with the invention and employing individual optical indicator means;
  • FIG. 6 is a variant of the portion of the fire alarm of FIG. 5 appearing at the left of the line AA thereof;
  • FIG. 7 is an embodiment of a conductor terminal element of FIG. ll;
  • FIGS. 81: to lie are diagrams serving to explain the mode of operation of the conductor terminal element shown in FIG. 7;
  • FIG. 9 is a block diagram of a central signal station.
  • the fire alarm installation depicted by way of example in FIG. it consists of a number n of two-poled fire alarms M M M, which are arranged parallel to one another and connected via two supply conductors l and 2 with a central signal station 82.
  • the individual fire alarms M M M are of identical construction and essentially consist of a circuit which, in the normal operational condition, exhibits high internal resistance for supply voltages U of a first polarity and a low internal resistance for supply voltages of a second polarity and which, in the event of an alarm, reverses this resistance relationship.
  • a circuit which fulfills these conditions is illustrated in a simplified form in the block of the fire alarm designated M
  • the circuit comprises two diodes 3 and 43, each of which is provided with a respective series connected resistor and 6.
  • the diodes 3 and 4 are oppositely poled, whereby the anode of diode 3 and the cathode of diode 4 collectively form one pole of the fire alarm and are connected to the supply conductor 1.
  • a switch 7, depending upon its position is connecting the resistor 5 or 6, respectively, with the other pole of the fire alarm or the supply conductor 2.
  • the position of switch 7 is determined by a nonillustrated apparatus which, as a function of the measured concentration of smoke, of changes in the ambient temperature, or of different criteria indicative of a fire, triggers a switching operation upon exceeding a threshold value.
  • Apparatus which are contemplated for this purpose are those equipped with ionization chambers, thermoelemcnts, optical smoke-measuring devices, or flame alarm devices.
  • switch 7 is located in the indicated full-line position.
  • diode 3 is conductive and the current flowing through the fire alarm is essentially determined by the resistor 5.
  • diode 3 blocks and practically no current flows through the fire alarm.
  • the fire alarm M comprises a relatively low impedance determined by the resistor 5 for positive supply voltages U, and, on the other hand, for negative supply voltages -U, the fire alarm M comprises a high impedance.
  • a pulse-shaped voltage u is delivered to the supply conductors l and 2.
  • the pulse-shaped voltage u possesses positive components 11 (positive pulses) and negative components 12 (negative pulses) with respect to the zero line 10.
  • a different voltage shape exhibiting both positive and negative amplitudes, such as a trapezoidal-shaped voltage, sinusoidal oscillations, and so forth. If all of the fire alarms M M M assume a normal operating condition or state, then a low impedance is exhibited for the positive pulses 11, the low impedance being practically determined by the parallel connection of all resistors 5 in FIG.
  • alarm-simulating conditions are periodically delivered to the fire alarms in order to be able to thereafter check at the central station whether or not all fire alarms have responded.
  • the delivery or transmission of the alarm-simulating conditions can take place in a standard manner known to the art, a particularly advantageous technique being described hereinafter in greater detail.
  • the purpose of checking with regard to functional or operational reliability is to determine whether all fire alarms have responded or whether one or a number of fire alarms have not responded. To this end, the behavior of the group of fire alarms with respect to the positive voltage pulses is observed at the central station. If during the checking operation all of the fire alarms have responded, then during the positive voltage pulses 11 (FIG. 2a) practically no current 13" (FIG. 2d) flows through the group of fire alarms, whereas there can be observed a clear deviation of the positive current pulses 13" (FIG. 2e) in the case of one or a number of defective fire alarms. Analogous to FIG. 2c, it will be observed from FIG. 2e that during the phase A, a fire alarm has not responded, whereas during the phase B, a second defective fire alarm appears.
  • FIG. 3 illustrates a first embodiment of a fire alarm which possesses the specific behavior or characteristics described in conjunction with the fire alarm M of FIG. 1.
  • Two ionization chambers 20 and 21 are connected in series with one another. Their point of connection or junction, generally formed by a common electrode in practice, is coupled to the control or gate electrode of a field-effect transistor 22.
  • ionization chamber 20 normally consists of a compartment which is closed at all sides and serves as a reference ionization chamber, whereas ionization chamber 21, functioning as a measurement chamber, is accessible to the surrounding air.
  • the second electrode of the reference ionization chamber 20 which is not connected with the gate electrode of the field-effect transistor 22 is connected via a junction or switching point 23 and a diode 3 with the supply conductor 1.
  • the source electrode of field-effect transistor 22 is coupled via a Zener diode 24 to the junction 23, whereas the drain electrode of field-effect transistor 22 is connected via a voltage divider comprising resistors 25 and 26, and the diode 4 with the supply conductor 1.
  • the base of a transistor 27 is connected to the top of voltage divider 25,26.
  • the emitter of transistor 27 is connected via a resistor 28 with the drain electrode of field-effect transistor 22 and is also connected via a capacitor 29 with the diode 4, as shown.
  • the emitter of transistor 27 is further coupled via a conductor 311 to the supply conductor 2, and via a capacitor 32 to junction 23.
  • the collector of the transistor 27 is connected via a resistor 30 with diode 4 and, via a voltage divider comprising resistors 33 and 34, with the junction 23.
  • the tap of the voltage divider 33,34 is coupled with the second electrode of the measurement ionization chamber 2i.
  • Capacitor 29 is designed or dimensioned to be so large that its voltage only slightly drops during the negative pulses, and thus can be considered to be constant.
  • a potential is applied to the gate electrode of field-effect transistor 22 which, on the one hand, is determined by the relationship of the resistors 30, 33 and 34 and, on the other hand, by the relationship of the internal resistance of the ionization chambers and 2ll.
  • the gate supply voltage of the field-effect transistor 22 is chosen in such a manner and is accommodated to the Zener voltage of Zener diode 24 such that field-effect transistor 22 conducts.
  • a current 13 flows during the positive pulses from the supply conductor l via the diode 3, Zener diode 24, field-effect transistor 22 and resistor 23, to the supply conductor 2.
  • Resistors 25 and 26 are dimensioned such that during the normal condition of operation, transistor 27 blocks.
  • capacitor 32 slightly discharges via the field-effect transistor 22 and transistor 27 continues to remain blocked. Only a relatively small current 114 (FIG. 2b) flows between the supply conductor 1 via diode 4, resistors 26,25 and 28, conductor 31, and the supply conductor 2. During this phase, capacitor 29 is charged to the negative supply voltage.
  • resistor 30 which, via both of the voltage dividers, resistors 33, 34 and ionization chambers 20, 21, additionally reduces the voltage between the gate electrode and the source electrode of fieldeffect transistor 22, whereby an increased smoke effect is simulated in the measurement ionization chamber. Accordingly, the circuit is positively fedback and shifts from the rest condition in self-holding fashion into the alarm condition. The alarm condition is maintained even after disappearance of the alarm-triggering conditions.
  • the remote triggering of the tire alarm or the attainment of alarm-simulating condition from the central station necessary for checking operational reliability can be undertaken in a number of different ways.
  • a simple possibility resides in reducing, for a short period of time, the positive pulse amplitudes of the supply voltage.
  • the reduction of voltage because of the voltage-stabilizing properties of the Zener diode 24, acts completely upon the source electrode of the field-effect transistor 22, whereas the potential at the gate electrode is only partially reduced or lowered due to the voltage dividers 33,34 and 20,21.
  • Field-effect transistor 22 now blocks and simulates the presence of smoke.
  • the positive voltage pulses 13 FIG.
  • the fire alarm circuit of HO. 3 althoughbeing particularly simple in construction, has the drawback that different components therein are not supervised or monitored. For example, an interruption in diode 4 results in capacitor 29 discharg ing via the resistors 33,34, whereby, the potential at the gate electrode of field-effect transistor 22 shifts towards positive values and causes such to block. Although the fire alarm is therefore apparently alarmed, an alarm function is nevertheless suppressed because of the interruption at the diode 4. During the checking operation, field-effect transistor 22 is nonetheless blocked in spite of this defect so that, during the positive voltage pulses, there is no current flow. During cutout of the diode 4, it is neither possible to determine the defect for itself nor an eventually occurring alarm.
  • the circuit arrangement shown in FIG. 4 overcomes these disadvantages, yet requires a greater expenditure because it uses a further transistor.
  • the gate electrode of field-effect transistor 22 is again connected to the common electrode of both ionization chambers 23 and 2t.
  • Zener diode 24 in series with the source electrode of the field-effect transistor 22 is now directly coupled with the supply conductor 2.
  • the drain electrode of fieldeft"ect transistor 22 is coupled via the voltage divider comprising resistors 25 and 26, to the junction or switch point 40, at which there is also connected the second electrode of the reference ionization chamber 20 and the emitter electrode of transistor 27.
  • the collector electrode of transistor 27 is coupled at the junction or switching point 41 with the second electrode of the measurement ionization chamber 211 and is connected via a resistor 46 with the supply conductor 2 as well as via a resistor 42 with the base electrode of a transistor 43.
  • the base electrode of transistor 43 is connected via a resistor 44 and the collector electrode via a re sistor 45 to the cathode of the diode 3, whereas the emitter electrode of transistor 43 is directly connected with the supply conductor 2.
  • the capacitor 2) is situated between the anode of diode 4 and the supply conductor 2. W hereas the field-effect transistor 22 in the circuit arrangement of FIG. 3 was conductive in the rest condition, now it blocks during the normal operating condition. Capacitor 29 is again charged to the negative operating voltage.
  • the voltage divider relationship: reference ionization chamber 2tl-series connection of the measurement ionization chamber 21, resistor 46 and the value of the Zener voltage of the Zener diode 24 are accommodated to one another such that the gate-source voltage of field-effect transistor 22 is below the response voltage thereof.
  • a voltage forms across the resistor 46, whereby thejunction point 41 becomes more negative.
  • the voltage drop at the resistor 46 is transmitted via the measurement ionization chamber 21 to the gate electrode of field-effect transistor 22, so that such becomes more conductive.
  • the field-effect transistor 22 and the transistor 27 therefore conjointly form a complementary switching stage with positive feedback.
  • the fire alarm which has responded remains self-holding. At the fire alarm which has responded, current flows during the negative voltage pulses on the one hand via diode 4, resistors 26 and 25, field-effect transistor 22 and Zener diode 24, and, on the other hand, via diode 4, transistor 27 and resistor 46 between the supply conductor 1 and the supply conductor 2 and serves for evaluation of the alarm at the central signal station.
  • the field-effect transistor begins to conduct and maintains this condition or state because of the positive feedback and the charge stored in the capacitor 29 also during the positive voltage pulses.
  • the negative voltage drop occurring across resistor 46 is transmitted via the voltage divider 42,44 to the base of transistor 43, so that transistor 43 is also blocked during the positive voltage pulses.
  • FIG. 5 A circuit arrangement in which all of the essential components of the fire alarm are checked with respect to their operational reliability is illustrated in FIG. 5.
  • the fire alarm circuit shown by way of example in such Figure is additionally designed particularly for low power consumption, contains protective devices for the most sensitive circuit components, and is additionally equipped with an optical indicating device for fire alarms which have responded or which are defective.
  • the gate electrode of field-effect transistor 22 is connected with the common electrode of the measurement ionization chamber 21 and the reference ionization chamber 20.
  • a resistor 34 is situated in parallel to the series connection of both ionization chambers and 21. Resistor 34, together with the resistor 33, forms a voltage divider.
  • the drain electrode of field-effect transistor 22 is coupled with the second electrode of the reference ionization chamber 20 and is connected via a resistor 60 with the anode of the diode 4.
  • the source electrode of field-effect transistor 22 is connected to the emitter electrode of a transistor 58, the collector electrode of which is connected via a resistor 59 to a conductor 57. Conductor 57 forms the second output of the fire alarm and provides the connection with the supply conductor 2.
  • the base electrode of transistor 58 is connected at the tap of a voltage divider formed by resistors 54 and 55, the voltage divider being directly connected between both supply conductors 1 and 2.
  • a capacitor 56 is connected in parallel with a resistor 55.
  • the capacitor 29 once again is located between the anode of diode 4 and the supply conductor 2, and the conductor 57, respectively.
  • the second electrode of the measurement ionization chamber 21 is connected via a diode 50 with conductor 57, whereas the second electrode of the reference ionization chamber 20 is coupled by means of a Zener diode 51 to conductor 57.
  • Transistors 64 and 68 collectively form a first complementary switching stage, whereby the voltage appearing across the resistor 59 is applied to the base electrode of transistor 68.
  • the emitter electrode of transistor 68 is directly connected with conductor 57.
  • the collector electrode of transistor 68 is coupled via the voltage divider, resistor 62 and resistor 63, to the anode of diode 4.
  • the base electrode of transistor 64 is connected at the tap of the voltage divider, the emitter electrode of which is directly connected with the anode of diode 47
  • the collector electrode of transistor 64 is lead back via the resistor 61 to the base electrode of transistor 68, and is further connected via a resistor 66 and glow lamp 67 with supply conductor 1 and finally via a voltage divider comprising resistor 65 and resistor 70, to the cathode of diode 3.
  • the base electrode of transistor 69 is coupled, the emitter electrode of which is coupled with conductor 57.
  • the collector electrode of transistor 69 leads via a voltage divider, comprising resistor 71 and resistor 72, to the cathode of diode 3.
  • the base electrode of transistor 73 is situated at the tap of the voltage divider 71,72, and its emitter electrode is directly connected with the cathode of diode 3, whereas the collector electrode, on the other hand, is connected via a resistor 74 to the base electrode of transistor 69 and, on the other hand, via a diode 63 to the resistor 33 of the voltage divider 33,34.
  • Transistors 69 and 73 collectively form a second bistable switching stage which is controlled by the first switching stage (transistors 64, 68) in a master-slave technique.
  • a capacitor 52 is connected between the cathode of diode 53 and the supply conductor 57.
  • capacitor 29 has been charged to the negative supply voltage and capacitor 52 to the positive supply voltage.
  • a voltage appears across the series connection of both ionization chambers 20 and 21 which is determined by the voltage divider relationship of the resistors 33,34 and 60.
  • the working or operating point of the gate electrode of field-effect transistor 22 is, analogous to the circuit of FIG. 4, chosen such that field-effect transistor 22 and therefore also transistor 58 block in the rest condition.
  • the Zener voltage of Zener diode 51 is greater than the voltage appearing during normal operational condition across the series connection of both ionization chambers, so that the Zener diode also blocks.
  • Zener diode 51 Only upon the appearance of possible overvoltages at the supply conductor 1 does the Zener diode 51 begins to conduct and produce a corresponding voltage drop across the resistor 60. Diode 50 insures that the second electrode of the measurement ionization chamber 21 starting from zero potential can only assume negative values.
  • a small leakage current flows only during the normal operation condition through field-effect transistor 22 and through transistor 58.
  • a voltage of practically zero appears across the collector resistor 59 and therefore also between the base and emitter electrode of transistor 68, so that transistor 68 also blocks.
  • the voltage divider 62,63 is without current, whereby transistor 64 likewise blocks due to the absence of a baseemitter voltage.
  • diode 3 conducts and draws a current through resistors 70, 65, 61 and 59. A voltage drop appears between the base and the emitter electrode of transistor 69 so that such begins to conduct and draws a collector current through the voltage divider 71 and 72, which, in turn, causes transistor 73 to conduct.
  • a current flows from the supply conductor 1 via diode 3 and essentially via transistor 69 to the supply conductor 2.
  • capacitor 52 is positively charged by means of diode 53.
  • diode 3 blocks and since the field-effect transistor 22 remains blocked, only a relatively small current flows in the capacitor 9 as well as across the voltage divider 54,55 to the supply conductor 2.
  • field-effect transistor 22 begins to conduct in the manner already described above.
  • a current flows between the supply conductor ll, via diode 4i, resistor Ml, field-effect transistor 22, transistor Ell, transistor till and the supply conductor 2.
  • Transistor 5% serves to form a response threshold for field-effect transistor 22 and replaces the Zener diode 2d of FIGS. 3 and l.
  • Its base electrode is prebiased by the charge stored in capacitor 56, whereby the voltage represents an average value of the negative and positive voltage pulses alternately appearing across resistor 55.
  • transistor '68 begins to conduct, and because of the current which now would flow via resistor 62 into the base electrode of transistor 6i, transistor 64 also begins to conduct, so that at the fire alarm which has been alarmed, a larger or greater current flows via both of these transistors between the supply conductor ii and the supply conductor 2, such being used in the central signal station for triggering an alarm.
  • the first bistable switching stage formed by both transistors d d and oil remains in a conductive state or condition until it is reset.
  • an indicating glow lamp 67 is employed which is connected in such a manner that it basically only tends to ignite during the positive pulses of the supply voltage.
  • the voltage applied across glow lamp 67 during the positive voltage phases is determined by the voltage divider resistor 59,61 and resistors 65,70 and is smaller than the response voltage of glow lamp 467.
  • the potential at the collector electrode of transistor 64 becomes more negative, thus the voltage across glow lamp s7 is increased during the positive pulse phases.
  • glow lamp s !
  • the response voltage of the glow lamp s1 is chosen such that the glow lamp, both when a fire alarm has responded or when transistor 64! is conductive, still does not ignite.
  • the remote triggering of the tire alarm for the purpose of checking can take place in a number of different ways, for example, by increasing the positive voltage pulse amplitudes.
  • One very sophisticated technique is to increase the repetition frequency of the positive pulses or to decrease their periods, whereby the average value of the direct'current voltage across capacitor 56 increases, which once again brings about a increase of the source-gate voltage of field-effect transistor 22, and such responds.
  • transistors 58,64 and Mt begin to conduct.
  • the collector electrode of transistor o l becomes strongly negative, so that with a suitable voltage divider relationship of the resistors as and 7d during the positive pulse phases, the base electrode of transistor as becomes more negative than its emitter electrode and transistor 69 remains blocked.
  • transistor 73 also remains blocked so that during the positive impulse phases with the tire alarm intact, current can no longer flow from the supply conductor l to the supply conductor 2.
  • the capacitor 52 does not receive any new charge during the positive pulse phases, so that it discharges to the null value.
  • the potential of the gate electrode of field-effect transistor 22 becomes more negative due to the discharging of capacitor 52. This corresponds to the positive feedback already described in connection with FiGS. 3 and i, but now the self-holding of an alarmed fire alarm is brought about in the Ml first instance by the bistable switching circuits Mott and 15%,73, respectively, which have switched into their other strible state or position.
  • the circuit arrangement according to FIG. 5 manifests it self, among other things, by the fact that it provides a high degree of supervising or monitoring possibilities for the in dividual components.
  • a defect in any one of the structural components at the actual region or part of the fire alarm brings about a blocking of transistors did and 45% ⁇ , whereby during the checking phase, transistors 69 and. "73 further conduct and therefore deliver a disturbance signal ll3' (FIG. 2e) to the central station.
  • An interruption at the actual monitoring circuit (elements beneath the conductor 57) on the other hand, causes a discharge of capacitor 52 and therefore a response of field-effect transistor 22, which, during the normal operating condition, indicates a (false) alarm.
  • defects can also simultaneously occur in both circuit portions which, under these circumstances, will not be determined by the remote checking operation. However, this type of situation is highly improbable and can be taken into consideration without any great drawback.
  • a practical disadvantage of the circuit arrangement of FIG. 5 resides in the fact that the second electrode ofthe measurement ionization chamber 2ll is connected via the diode 54) with the supply conductor 2 which is generally grounded.
  • the substrate electrode tit) of field-effect transistor 22 is connected instead with the tap of the voltage divider comprising resistors 33 and 34-, rather than with the source electrode.
  • FIG. 6 is a variation of the portion of the circuit arrangement to the left of the section line A-A of FIG. 5.
  • FIG. '7 depicts an embodiment of a conductor terminal element which can be used to particular advantage in conjunc tion with the inventive fire alarm installations.
  • the function of this conductor terminal element resides in indicating at the central station a possibly occurring break or interruption at the conductor means of the groups of tire alarms.
  • the exemplary illustrated conductor terminal] element here shown consists of an asymmetrical astable multivibrator which is connected via a diode ill to the supply conductor l as well as directly to the supply conductor 2. Both of the transistors $2 and M are coupled with the supply conductor 2 through the agency of a respective collector resistor as and $9.
  • the base electrodes of both transistors $2 and 83 are coupled or connected with the junction or tap of a respective voltage divider circuit incorporating resistors 84.285 and 87b8, respectively.
  • the emitter electrode of transistors b2 and 83 are directly connected with the anode of a diode 81.
  • a capacitor W is ar' ranged between the base electrode of transistors 83 and the collector electrode of transistor 82, and, between the base electrode of transistor $2 and the collector electrode of transistor $3, a capacitor 91 is placed.
  • FIG. 8a initially shows once again the pulse-shaped voltage 14 applied between the supply conductors 1 and 2 and appearing at both inputs of a conductor terminal element. It will be recognized that FIG. 8a is identical to FIG. 2a.
  • FIG. 8c shows, at the left of the line SS, the current i flowing through the group of fire alarms during the normal operating condition and represents a superimposition of FIGS. 2b and 8b, whereas at the right of the line SS there is indicated the current i received at the central station when a fire alarm is alarmed or has responded, and which results from superimposing the current shown in FIGS. 20 and 8b.
  • pulses continually appear at the central station, the repetition frequency of which is considerably greater than that of the supply voltage pulses and which therefore can be easily separated by means of a frequency branching or selective network.
  • An absence of the pulses of the conductor terminal element signifies a conductor break or interruption or a possible defect in the conductor terminal element itself.
  • Two threshold value detectors 103 and 104 received the voltage drop appearing across the resistor 102, whereby by switching in diodes 105 and 106 of different polarity, the threshold value detector 103 measures the positive voltage drops and the threshold value detector 104 measures the negative voltage drops.
  • the threshold value detector 103 is controlled by the control device 101 in such a manner that, during the checking operation, a disturbance alarm is triggered when the positive voltage drop across the resistor 102 exceeds a certain threshold value.
  • the threshold value detector 104 is controlled by the control device 101 in such a manner that, at its output 107, only those negative signals appearing across the resistor 102 are transmitted which, during the normal operation exceed a certain negative threshold value.
  • unit 108 measures the signals with high frequency derived or coming from the conductor terminal element and, in the absence thereof, triggers a disturbance signal
  • unit 109 measures the signals with low frequency and, during their occurrence, triggers a smoke or fire alarm.
  • circuit arrangements illustrated in FIGS. 3 to 6 are only preferred, exemplary embodiments of fire alarms which are particularly well suited for use in a fire alarm installation of the inventive type shown in FIG. 1. It is quite readily possible to use other circuits and, in particular, individual components or groups of structural components can be replaced by equivalent different components, such as replacing transistors by tubes and the like.
  • a fire alarm installation comprising:
  • a pair of common conductors for connecting said plurality of fire alarms in parallel to one another and to said central station;
  • each of said fire alarms comprising a detector element sensitive to fire phenomena and electric circuit means controlled by its associated detector element;
  • each of said circuit means possessing two stable conditions, defining a normal condition when the detector element assumes a normal operating state in a condition of readiness for detecting a fire and an alarm condition when said detector element assumes a response condition when it has been subjected to fire phenomena f. said circuit means possessing two parallel current paths for the respective flow of currents of different polarity;
  • each of said circuit means including switching means for connecting one of said parallel current paths to said two common conductors when the circuit means is in said normal condition and for connecting the other of said current paths across said two conductors when the circuit means is in said alarm condition;
  • said central station embodying means for generating a supply voltage of continuously and periodically alternating polarity which is delivered to said two conductors;
  • said central station further including means for generating a test signal applied to said two conductors; said test signal controlling said electric circuit means in like manner as said detector elements; and
  • said central station further comprising measuring means for separately detecting the current in said two conductors during the phases of different polarity of said supply voltage.
  • each of said detector elements comprises a measuring ionization chamber accessible to the surrounding atmosphere, at least one resistance element connected in series with said measuring ionization chamber, the current flowing through said measuring ionization chamber changing when the atmosphere contains combustion aerosols or smoke, each of said circuit means being responsive to the thus produced voltage changes appearing across its associated measuring ionization chamber.
  • each of said circuit means comprises two circuit branches, each circuit branch being connected across said supply conductors via respective diode means of opposite polarity and via controllable semiconductor means, said controllable semiconductor means being connected in said circuit means such that one of said semiconductor means is conductive and the other semiconductor means is blocked during said normal condition of said electric circuit means, whereas said one semiconductor means is blocked and said other semiconductor means is conductive during said alarm condition of said electric circuit means.
  • each of said detector elements comprises a measuring ionization chamber accessible to the surrounding atmosphere connected in series with a reference ionization chamber by a common electrode, said one controllable semiconductor means being a field-effect transistor having gate, source and drain electrodes, the gate electrode of which is electrically con nected with said common electrode of both said ionization chambers, said other semiconductor means being a further transistor, said circuit means possessing voltage divider means for coupling both saidionization chambers with said further transistor such that said field-effect transistor is positively fed back by means of said further transistor as well as by said ionization chambers.
  • each of said detector elements comprises a measuring ionization chamber accessible to the surrounding atmosphere connected in series with a reference ionization chamber by a common electrode, one of said two transistors of said bistable ele' ment being a field-effect transistor having gate, source and drain electrodes, the gate electrode of which is connected to said common electrode of both ionization chambers, said further transistor having a base electrode, the second transistor of said bistable element possessing a collector elec trode connected with a second electrode of one of the ionization chambers and with said base electrode of said further transistor in the other current path and via a resistor with one of the supply conductors, said bistable element being connected via one of said diode means with the other of said supply conductors, one said electrode of said field-effect transistor being connected via a Zener diode with said one supply conductor, said further transistor in said other current branch being connected via the other of said diode means with said other supply conductor.
  • a fire alarm instaHation as defined in claim t wherein one of said current paths comprises a first diode and a first bistable element containing at least two transistors, said second current path comprises a second diode connected electrically antiparallel to said first diode and a second bistable element comprising at least two further transistors, said second bistable element being connected with and controlled by said first bistable element such that only one of said bista ble elements is conductive and the other one is blocked.
  • each of said detector elements comprises a measuring ionization chamber accessible to the surrounding atmosphere connected in series with a reference ionization chamber by a com mon electrode, a field-effect transistor having a gate, drain and source electrode and controlling said first bistable element, said gate electrode of said field-effect transistor being connected to said common electrode of said two ionization chambers, 21 still further transistor providing an alarm threshold means connecting said field-effect transistor with said first bistable element, said field-effect transistor and said first bistable element being blocked when said circuit means is in said normal condition, said second bistable element being further connected via a diode with a capacitor and with a voltage divider for connecting said second bistable element with the series connection of both of said ionization chambers, said further capacitor during the normal condition of said circuit means being charged and in said alarm condition discharges due to blocking of said second bistable element and thereby id stores said alarm condition by displacing the potential at said gate electrode of said field-effect transistor.
  • An alarm installation comprising a central station, a plurality of alarms, at least one pair of conductors for electrically connecting said plurality of alarms in a group in parallel with said central station, said central station including supply voltage means for said group of parallely connected alarms, a conductor terminal element means connected in parallel to the last alarm of said plurality of alarms for monitoring possible interruptions at the conductors of said plurality of alarms, said conductor terminal element means including means for applying to said conductors a signal having an alternating voltage component for periods during which said central station is delivering a supply voltage of a certain polarity to said conductors and different from the signals drawn by said plurality of alarms.
  • An alarm installation comprising a central station, a plurality of alarms, at least one pair of conductors for electrically connecting said plurality of alarms in a group in parallel with said central station, said central station including supply voltage means for said group of parallely connected alarms, a concluctor terminal element means connected in parallel to the last alarm of said plurality of alarms for monitoring possible interruptions at the conductors of said plurality of alarms, said conductor terminal element means including means for applying to said conductors a signal different from the signal delivered by said supply voltage means to said plurality of fire alarms and different from the signals drawn by said plurality of alarms, said supply voltage means delivering signals of alter nating polarity, said terminal element means applying to said conductors a signal of a different: frequency than the signal frequency of said supply voltage means.
  • An alarm installation comprising a central station, a plurality of alarms, at least one pair of conductors for electrically connecting said plurality of alarms in a group in parallel with said central station, said central station including supply voltage means for said group of parallely connected alarms, a con ductor terminal element means connected in parallel to the last alarm of said plurality of alarms for monitoring possible interruptions at the conductors of said plurality of alarms, said conductor terminal element means including means for applying to said conductors a signal different from the signal delivered by said supply voltage means to said plurality of fire alarms and different from the signals drawn by said plurality of alarms, said supply voltage means delivering a signal of altcr nating polarity, said means of said conductor terminal element means for applying said signal to said conductors comprises an asymmetrical astable multivibrator having a higher pulse repetition frequency than the repetition frequency of said supply voltage means.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Fire Alarms (AREA)
US738046A 1967-06-26 1968-06-18 Fire alarm installation Expired - Lifetime US3603949A (en)

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Application Number Priority Date Filing Date Title
CH903167A CH468682A (de) 1967-06-26 1967-06-26 Feuermeldeanlage

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US3603949A true US3603949A (en) 1971-09-07

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US738046A Expired - Lifetime US3603949A (en) 1967-06-26 1968-06-18 Fire alarm installation

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US (1) US3603949A (de)
AT (1) AT275365B (de)
CH (1) CH468682A (de)
DE (1) DE1766440C3 (de)
FR (1) FR1569514A (de)
GB (1) GB1228931A (de)
NL (1) NL165311C (de)
SE (1) SE328225B (de)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3702468A (en) * 1970-08-10 1972-11-07 Nittan Co Ltd Fire alarming system
US3748389A (en) * 1971-12-13 1973-07-24 Bell Telephone Labor Inc Alarm detection system
US3811126A (en) * 1972-06-07 1974-05-14 Smelting Refining And Mining C Alarm system
US3832678A (en) * 1970-11-12 1974-08-27 B Gysell Fire alarm system
US3978461A (en) * 1975-05-12 1976-08-31 Firetek Corporation Three wire detection circuit
US3987319A (en) * 1974-12-05 1976-10-19 The United States Of America As Represented By The Secretary Of The Army Radiation-activated sensor
US3991413A (en) * 1975-06-23 1976-11-09 Berger Philip H Constant current detector system
US3997890A (en) * 1974-06-11 1976-12-14 Kendrick Jr Embry Mayes Alarm system with supervisory system to detect severing or bridging of detection switches
US4023152A (en) * 1973-10-01 1977-05-10 Matsushita Electric Works, Ltd. Ionization type smoke sensing device
US4097851A (en) * 1976-07-19 1978-06-27 Pittway Corporation Sensitivity compensated fire detector
US4213046A (en) * 1977-02-21 1980-07-15 Hartwig Beyersdorf Ionization fire-signal device
US4385287A (en) * 1979-12-07 1983-05-24 Securicor Granley Systems Limited Multiple alarm condition detection and signalling
US4404548A (en) * 1980-06-23 1983-09-13 Cerberus Ag Method for transmitting measuring values in a fire alarm system and apparatus for the performance of the aforesaid method
US4481502A (en) * 1982-03-26 1984-11-06 Dawson N Rick Central smoke alarm and annunciator
US4916432A (en) * 1987-10-21 1990-04-10 Pittway Corporation Smoke and fire detection system communication
EP1555642A1 (de) * 2002-10-10 2005-07-20 Valery Vasilievich Ovchinnikov Verfahren zum bilden und senden von signalen
US20060290389A1 (en) * 2005-06-23 2006-12-28 Honeywell International, Inc. Flame detector trapezoidal excitation generator output control circuit and method
US20070008077A1 (en) * 2005-06-17 2007-01-11 Claiborne Jimmy D Reversible diode doorbell detection circuit
GB2429317A (en) * 2005-08-16 2007-02-21 Bosch Gmbh Robert Security system using an AC primary line
US20100073175A1 (en) * 2008-02-08 2010-03-25 Lontka Karen D Methods and apparatus for controlling and testing a notification applicance circuit
US20160314668A1 (en) * 2015-04-22 2016-10-27 Hong Fu Jin Precision Industry (Wuhan) Co., Ltd. Alarm circuit for electronic device

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DE2454196C3 (de) * 1974-06-14 1985-02-07 Cerberus AG, Männedorf, Zürich Brandmeldeanlage
CH606916A5 (de) * 1976-10-22 1978-11-15 Landis & Gyr Ag
DE2713280C3 (de) * 1977-03-25 1986-10-23 Esser Sicherheitstechnik GmbH & Co KG, 4040 Neuss Funktionsüberprüfbare Feuermelderanlage
DE2939494B2 (de) * 1979-09-28 1981-07-02 Siemens AG, 1000 Berlin und 8000 München Schaltungsanordnung für Einbruch- oder Feuermeldea nlagen
GB2138570B (en) * 1983-04-19 1987-10-28 Emi Ltd Smoke detector
GB2149167B (en) * 1983-11-04 1987-04-08 Graviner Ltd Electrical circuit arrangements in fire alarms
RU2232425C2 (ru) * 2002-10-10 2004-07-10 Овчинников Валерий Васильевич Способ формирования и передачи сигналов
CN107045762B (zh) * 2017-04-14 2023-08-11 重庆和航科技股份有限公司 电气火灾远程监测动态预警方法及系统

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Publication number Priority date Publication date Assignee Title
US3029420A (en) * 1957-02-25 1962-04-10 Kidde & Co Walter Network for monitoring alarm systems
US3176284A (en) * 1963-09-27 1965-03-30 Specialties Dev Corp System responsive to plural conditions with false indication prevention
US3351934A (en) * 1965-05-19 1967-11-07 Honeywell Inc Supervised alarm system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3029420A (en) * 1957-02-25 1962-04-10 Kidde & Co Walter Network for monitoring alarm systems
US3176284A (en) * 1963-09-27 1965-03-30 Specialties Dev Corp System responsive to plural conditions with false indication prevention
US3351934A (en) * 1965-05-19 1967-11-07 Honeywell Inc Supervised alarm system

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3702468A (en) * 1970-08-10 1972-11-07 Nittan Co Ltd Fire alarming system
US3832678A (en) * 1970-11-12 1974-08-27 B Gysell Fire alarm system
US3748389A (en) * 1971-12-13 1973-07-24 Bell Telephone Labor Inc Alarm detection system
US3811126A (en) * 1972-06-07 1974-05-14 Smelting Refining And Mining C Alarm system
US4023152A (en) * 1973-10-01 1977-05-10 Matsushita Electric Works, Ltd. Ionization type smoke sensing device
US3997890A (en) * 1974-06-11 1976-12-14 Kendrick Jr Embry Mayes Alarm system with supervisory system to detect severing or bridging of detection switches
US3987319A (en) * 1974-12-05 1976-10-19 The United States Of America As Represented By The Secretary Of The Army Radiation-activated sensor
US3978461A (en) * 1975-05-12 1976-08-31 Firetek Corporation Three wire detection circuit
US3991413A (en) * 1975-06-23 1976-11-09 Berger Philip H Constant current detector system
US4097851A (en) * 1976-07-19 1978-06-27 Pittway Corporation Sensitivity compensated fire detector
US4213046A (en) * 1977-02-21 1980-07-15 Hartwig Beyersdorf Ionization fire-signal device
US4385287A (en) * 1979-12-07 1983-05-24 Securicor Granley Systems Limited Multiple alarm condition detection and signalling
US4404548A (en) * 1980-06-23 1983-09-13 Cerberus Ag Method for transmitting measuring values in a fire alarm system and apparatus for the performance of the aforesaid method
US4481502A (en) * 1982-03-26 1984-11-06 Dawson N Rick Central smoke alarm and annunciator
US4916432A (en) * 1987-10-21 1990-04-10 Pittway Corporation Smoke and fire detection system communication
EP1555642A4 (de) * 2002-10-10 2005-10-26 Valery Vasilievich Ovchinnikov Verfahren zum bilden und senden von signalen
EP1555642A1 (de) * 2002-10-10 2005-07-20 Valery Vasilievich Ovchinnikov Verfahren zum bilden und senden von signalen
US7365637B2 (en) 2005-06-17 2008-04-29 Heathco Llc Reversible diode doorbell detection circuit
US20070008077A1 (en) * 2005-06-17 2007-01-11 Claiborne Jimmy D Reversible diode doorbell detection circuit
US20060290389A1 (en) * 2005-06-23 2006-12-28 Honeywell International, Inc. Flame detector trapezoidal excitation generator output control circuit and method
EP1739353A1 (de) * 2005-06-23 2007-01-03 Honeywell International Inc. Ausgangssteuerkreis und Verfahren eines Generators zur trapezförmigen Erregung eines Flammendetektors
US7553152B2 (en) 2005-06-23 2009-06-30 Honeywell International Inc. Flame detector trapezoidal excitation generator output control circuit and method
GB2429317B (en) * 2005-08-16 2007-12-19 Bosch Gmbh Robert Security device
GB2429317A (en) * 2005-08-16 2007-02-21 Bosch Gmbh Robert Security system using an AC primary line
US20100073175A1 (en) * 2008-02-08 2010-03-25 Lontka Karen D Methods and apparatus for controlling and testing a notification applicance circuit
US8446285B2 (en) * 2008-02-08 2013-05-21 Siemens Industry, Inc. Methods and apparatus for controlling and testing a notification appliance circuit
US20160314668A1 (en) * 2015-04-22 2016-10-27 Hong Fu Jin Precision Industry (Wuhan) Co., Ltd. Alarm circuit for electronic device
US9715982B2 (en) * 2015-04-22 2017-07-25 Hong Fu Jin Precision Industry (Wuhan) Co., Ltd. Alarm circuit for electronic device

Also Published As

Publication number Publication date
CH468682A (de) 1969-02-15
NL165311C (nl) 1981-03-16
DE1766440C3 (de) 1979-03-08
NL165311B (nl) 1980-10-15
AT275365B (de) 1969-10-27
FR1569514A (de) 1969-05-30
GB1228931A (de) 1971-04-21
NL6808477A (de) 1968-12-27
SE328225B (de) 1970-09-07
DE1766440B2 (de) 1974-10-03
DE1766440A1 (de) 1971-07-15

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