DE2710046A1 - Distributed fire alarm network - has maintenance checking facility for all local transducers and circuits when suitably primed from central control - Google Patents

Abstract

In the distributed fire alarm network a number of local units (A) are connected in parallel across a cable pair (L1, L2) to a central alarm station (B). Each local station contains a transducer (1), an alarm signal generator (2) and a current limiter (3), and in addition, a timing network (4) a test signal circuit (6) and a faulty operation signal circuit (5) connected in parallel with the fire alarm signal generator (2) and current limiter (3). The central control contains two separate circuits, selected by a switch (11), one of which supplies and monitors normal operation (7, 9) while the other (8, 10) provides a different, possibly reversed voltage for test purposes and a corresponding detector circuit (8). When a test is conducted, the test signal circuit (6) at each local monitor point, accepts the test signal from the central station on the cable pair and primes the timing network and the fire transducer.

Description

Fire alarm system

The invention relates to a fire alarm system with a pair of signal lines fire detectors connected in parallel to a signal center, the signal center a test signal to check the functionality of the connected fire detectors able to deliver to the signal lines.

The fire detectors of such a system contain fire sensors that certain fire phenomena react, e.g. to smoke, fire aerosol, fire gases, flames or to a temperature increase, and which in the event of a fire a fire alarm device press, which generates an alarm signal in the signal lines, e.g. an increase in current, triggers.

In such fire alarm systems it is necessary from time to time to check whether the connected fire detectors correctly indicate a fire outbreak react. It is known to send a test signal from the signal center for this purpose, E.g. a voltage change to the signal lines, whereby the to these Lines connected, operational fire detectors in same Wise made to respond, such as in the event of a fire.

The arrival of the alarm signals from the fire detectors in the signaling center then shows that the connected fire detectors respond properly and are functional are.

Such a system is completely sufficient if only one fire detector or only a few fire detectors connected to the signal center via the same lines are, however, it is not enough to be safe with many connected fire detectors to be able to recognize in the signal center whether all fire detectors have been addressed or whether one of the connected fire detectors is not functioning properly. One reason for this is that a single detector already addressed the Lines short-circuit and thereby the voltage for the actuation of the rest Fire detector can no longer be sufficient.

The object of the invention is to remedy this previously known disadvantage Eliminate fire alarm systems and in particular a fire alarm system with many fire detectors connected in parallel via a pair of signal lines, which are sent by the control center can be made to respond by means of a test signal, to be designed in such a way that that can be determined safely and with simple means by the signal center can check whether all connected fire detectors are faultless during the function tests have responded or whether one of the fire alarms is not working properly.

According to the invention, this object is achieved by the characterizing features of the claims solved. The individual fire detectors each contain one Circuit that responds to the test signal and, on the one hand, the sensing element of the Causes the fire detector to respond, on the other hand sets a timer in operation, which in turn controls a fault signal generator.

This triggers a fault signal if the fire sensor is not within the running time of the timer responds, but does not react if the corresponding Has responded correctly to the detector. The triggering of a fault signal can therefore in the signal center as a sign of not being flawless working fire alarms. To avoid interference from the alarm currents of the Avoiding fire detectors that are triggered when they respond normally is one thing Current limiting device is provided, which causes the sum of the alarm currents of all connected detectors is less than a fault signal, so that a fault can be recognized properly.

Using the circuit diagrams shown in the figures, exemplary embodiments of the invention described.

Figures la and lb show block diagrams of two different ones Embodiments.

FIGS. 2-4 show detailed circuit diagrams of three exemplary embodiments according to figure lb.

In the examples according to Figure la and lb, a fire alarm A is above Signal lines L1, L2 connected to a signal center B. Others, not shown Fire detectors can be connected in parallel to fire detector A. The fire detectors included a fire sensor 1, which controls an alarm signal generator 2 in the event of a fire, which is in series with a current limiting device 3 (in Figure la) or 3 '(in Figure lb) lies between lines L1 and L2. In the event of a fire, the alarm signal generator switches 2 alf passage and an alarm current flows in the signal lines.

For the purpose of functional testing, the fire detectors continue to contain a timing circuit 4 which is controlled by the output of the alarm signal generator 2 is, a disturbance signal generator 5, which is controlled by the output of the timer 4 is, and a test signal switch 6, which is actuated as soon as the signal lines L1 and L2 a test signal from the control center occurs, and which both the fire sensor 1 as well as the timer 4 controls, and according to the example Figure lb also the current limiter 3 '.

In addition to an alarm signal detector 7 (in Figure la) and 7 '(in Figure lb) a first voltage source 9, a second voltage source 10 with a different voltage or reversed voltage polarity and a changeover switch 11, which during normal operation the voltage source 9 with the lines L1 and L2 connect, and the other voltage source 10 during the test process. In the example according to FIG. 1 a, the alarm signal detector 7 is located between changeover switches 11 and voltage source 9 'while between the changeover switch 11 and the test voltage source 10 a fault signal detector is connected. Against this is the example after Figure lb only a single signal detector 7 'is provided in series with the switch 11, because the voltage limiter 3 'in the fire alarms only works during the test process and suppresses the alarm signals.

The test signal receiving circuit 6 of the fire alarm A is now designed so that it does not respond to the voltage of the voltage source 9 and no output signal supplies. Therefore, the timer circuit 4 is not put into operation and the fault signal generator 5 cannot be operated either. If the fire sensor 1 is a fire phenomenon registered, it generates an output signal as soon as the corresponding fire phenomenon occurs has exceeded a predetermined threshold and activates the alarm signal generator 2, which e.g. switches from the non-conductive to the conductive state and the lines shorts. In the example according to Figure la, however, prevents the permanently switched on Current limiting circuit 3 that too high a current is flowing in lines L1 and L2, when the alarm signal transmitter 2 has been activated. In the signal center is then through the alarm signal detector 7, which is switched on via the switch 11 in normal operation is, the occurrence of an alarm current is proven and a fire alarm is signaled.

During the functional check, the example according to Figure la is the Switch 11 switched to the other voltage source 10.

The test signal switch 6 thus receives a different voltage or a voltage of reverse polarity and sets the timer 4 in operation. At the same time, if the sensor 1 is normal, it becomes similar stimulated, as if a fire phenomenon were present, so it was sent to the alarm circuit 2 emits a signal. By this alarm signal, i.

due to the change in potential at the connection point between the alarm signal generator 2 and the current limiter 3, the timer circuit 4 is blocked at the same time, so that he can not operate the fault signal generator 5 and only the one through the current limiter 3 limited alarm current flows in lines L1 and L2.

On the other hand is held in the signal central by the switch 11 of the alarm signal generator 7, a fault signal generator 8 has been switched on, which is designed so that he himself is based on the sum of the alarm currents all in parallel switched fire detector does not respond. However, since the disturbance signal is not limited it can be detected by the fault signal detector 8 in the signal center, as soon as it is through one of the timer circuits 4 after the specified time delay time has elapsed is triggered in lines L1 and L2. By means of this interference signal detector 8 it can therefore be reliably detected in the signaling center 13 whether one of the detectors A is disturbed.

In this exemplary embodiment according to FIG. La, the value is dcromes in lines L1 and B2 in the event of a fire alarm, i.e. when the alarm signal transmitter 2 is activated and in the event of a fault, i.e.

when actuating the fault signal generator 5, differently, depending on the situation whether the current flows through the current limiter 3 or not. In the signal center B the currents are detected in both cases by different devices and an inoperative fire detector is displayed. For example, if a number of a maximum of 20 fire detectors, each with 10 (> z Quiescent current in a monitoring zone connected to the signal center via lines L1 and L2 the maximum quiescent current is 2 mA. In this case it is recommended to design the alarm current limiter 3 to 4 mA and the alarm signal detector 7 in the Train the control center in such a way that it responds to a current of 3 mA during the Disturbance signal detector 8 should have a response current of 100 mA.

In the example of Figure lb is different from the above described example the current limiting circuit 3 'is not switched on continuously, but is only switched on by the test signal switch 6 of the fire detector when a test signal arrives, but not during normal monitoring operation. When fire sensor 1 or alarm device 2 responds, the full flow therefore flows Alarm current via lines L1 and L2 to signal center B. In this case, it is it is therefore possible to choose the alarm current as large as the disturbance current.

Therefore, in the signal center for detection of the alarm signal and of the fault signal, the same current detector 7 'is used as a common display circuit will. During the surveillance operation, an alarm current from a fire detector is activated while the test blocks the alarm currents through the current limiter 3 ' and only a malfunction signal from a non-functioning fire detector is displayed will. Otherwise, the circuit according to FIG. 1b works analogously to the example Figure la.

In the detailed circuit diagram of an exemplary embodiment shown in FIG According to a circuit according to FIG. 1b, each fire alarm A contains a fire detection part Al, which is the fire sensor, the alarm signal generator and part of the test signal switch contains, as well as a fault detector part A2, the current limiter 3 ', the timer circuit, contains the fault signal transmitter and the remaining part of the test signal switch. The test voltage source in the associated signal center is designed in such a way that that it delivers a higher voltage than that during normal Voltage source switched on during monitoring operation.

The fire detection part Al contains a series circuit a Zener diode D2 and a resistor R5 as parts of the test signal switch, one Series connection of a transistor T1 with a resistor R1 and a zender diode D3 and a thyristor S1 as an alarm signal generator. The base of transistor T1 is with the connection point a of a thermistor Th and a resistor R0, which in Are connected in series and together with a parallel connected Zener diode D2 form the fire sensor, connected.

The fire detector part Al is on the one hand with a line L1 'over a current limiting circuit 3 'in the fault detector part A2 with the negative signal line L1 connected in such a way that the current is only limited during the functional test is, on the other hand with a line L2 'directly to the positive signal line L2. This current limiting circuit 3 'located between the lines L1' and L1 comprises a current stabilizer, which is through a field effect transistor T2 and a between Source and gate electrode of the field effect transistor T2 connected resistor R2 is formed, as well as a parallel connection of a resistor R7 and a transistor T5 connected in series with the current stabilizer and through a thyristor S3, which is controlled by the voltage drop across resistor R7 and the like parallel to the entire series circuit.

The remainder of the test signal switch includes a resistor R8, a zener diode D4 and a resistor R9 connected in series between the lines L1 and L2 'lie, the voltage drop across resistor R8 making the transistor T5 of the current limiting circuit 3 'controls. The timing circuit includes a resistor R6, the transistor T4 controlled by the voltage drop 9 between the Lines L1 'and L2 are connected, a capacitor C1, the is charged via a resistor R3 from the voltage drop across the resistor R6, as well as a field effect transistor T3, which is connected to a resistor R4, a Zener diode and D1 the transistor T4 between the lines L1 and L2 ', and its gate electrode connected to the junction of resistor R3 and capacitor C1 is. The fault signal transmitter finally comprises a thyristor S2 between the Lines lil and L2 ', whose controls electrode to the connection point of the resistor R4 is connected to transistor T3.

The mode of operation of this circuit is as follows: During normal During monitoring operation, the voltage on lines L1 and L2 corresponds to normal Monitoring voltage, which is below the Zener voltage of the Zener diodes D2 and D4 which are therefore blocked. Therefore, the transistors T4 and T5 are also blocked, and the capacitor C1 does not charge, the field effect transistor T3 and the thyristor S2 also remain locked and resistor 7 is not bridged. If now a If a fire breaks out, the resistance of the here as a fire sensor element is reduced acting thermistor Th, and the change in potential at point a becomes transistor T1 and thyristor S1 switched to continuity, so that a current through the current limiting circuit, formed by transistor T2 and resistor R2, and flows through resistor R7. This makes thyristor S3 conductive and the series circuit of transistor T2, resistor R2 and R7 are short-circuited. This has the consequence that a relatively large current Flows over the lines L1 and L2 to the signal center, where it flows through a current detector a fire alarm signal is triggered.

During the functional test of the detector A, the lines L1 and L2 in the signal center connected to a higher voltage than during of normal fire monitoring betricbes. This tension is higher than the zener tension the Zener diodes D2 and D4, which become conductive and the transistors Also switch T4 and T5 to continuity. By the falling across resistor R6 Voltage, the capacitor C1 of the timing circuit is charged and at the same time Resistor R7 shorted. On the other hand, the actuation of the zener diode causes D2, as long as the fire sensor part Al is in the normal state, another Voltage drop across resistor R5, through which the potential at point d and thus is also decreased at point a. This makes transistor T1 and thyristor S1 conductive and resistor R6 is shorted. As a result, the charge on the capacitor C1 interrupted and transistor T2 and thyristor S2 are not switched through. The current flowing through the lines L1 and L2 when the thyristor S1 is conductive flows so through the thyristor S1 and the current limiting circuit, which is through the field effect transistor T2 and the resistor R2 is formed, and the transistor T5. The thyristor S3 does not become conductive. The flowing current is therefore limited and the alarm current detector in the signal center is not actuated.

However, if the fire detector part Al does not work properly, switches Thyristor S1 not on continuity during the test process, even if the Zener diode D2 is conductive. The capacitor C1 can therefore continue to charge. If now that Charge voltage in a given time is the sum of the threshold voltages of the transistor T3 and the Zender diode exceeds D1, transistor T3 becomes conductive and thyristor S2 also becomes conductive due to the voltage drop across resistor R4, so that a relatively large currents flow via lines L1 and L2 to the signal center can, whereby the current detector is actuated and signals a fault.

The circuit diagram of Figure 2 corresponds to the example of Figure lb. By short-circuiting the resistors R7 and R8 and omitting the thyristor S3 and Transistor T5 can transform the circuit into the embodiment of Figure la will.

In Figure 3, the fire detection part Al comprises a fire sensor circuit with a thermistor Th in series with a resistor R0, whose connection point a is connected to the base of a transistor T1, and which is in series with resistors R1 and R10 lies, with a resistor Rv11 in parallel with transistor T1 and resistor R1 lies. A thyristor S1 whose control electrode is connected to the junction of the transistor T1 and resistor R1 are connected, forms the alarm signal generator.

This fire detection part Al is connected to the lines L1 'and L2'. The line L1 'is with the signal line L1 via a rectifier D6, the one Forms part of the test signal switch, together with rectifiers D7 and D9 and one Current limiting circuit 3 'connected. The signal line L1 only has during the test process a negative polarity, as indicated under the symbol t. Line L2 'is connected to the signal line L2 via a rectifier D7. During the functional test the line L2 has a positive polarity as indicated under the symbol t. While The functional test is a resistor R12 in parallel with a resistor Rll across connected to the rectifier D9 and a resistor R13 is in parallel with the resistor R10 switched via rectifiers D9 and D7. During normal fire monitoring on the other hand, the signal line L1 has a positive polarity, as shown under the symbol s and is in series with the line L2 'through a rectifier D5 a rectifier D10 in the current limiting circuit 3 'connected. The line L2 has reverse polarity 1 as shown under the symbol during fire monitoring s, and is connected to line L1 'via a rectifier D8.

The fault detector part A2 comprises the current limiting circuit 3 ' and the parts of the timer and the fault signal generator.

The current limiting circuit 3 'comprises a current stabilizer, the by a field effect transistor T2 and a resistor R2 between source and Gate electrode of this field effect transistor is formed7 and one parallel to it lying rectifier D10. The timing circuit includes a rectifier Dll and a resistor R3, which at the same time forms part of the test signal switch, and a capacitor C1, which is formed by the transistor T2 and resistor R2 The current stabilizer is charged by the voltage on the lines L1 and L2, and a field effect transistor T3, which is in series with the rectifier Dgl'einer Zener diode D1 and a resistor R4 between the signal lines L1 and L2, its gate at the junction of the resistor R3 and the capacitor C1 is connected. The fault signal generator includes a thyristor S2, whose Control electrode to the junction of resistor R4 and the field effect transistor T3 is connected.

The mode of operation of the circuit according to FIG. 3 is as follows: During the fire monitoring system, a certain voltage is applied to the signal lines L1 and L2 Polarity as marked with the symbol s, i.e. the line L1 is positive and the line L2 negative. As a result, rectifier Dll is blocked, the capacitor C1 of the timing circuit is not charged, and the field effect transistor T3 and Thyristor S2 are also blocked. When transistor T1 and thyristor S1 as a result a decrease in resistance of the thermistor Th in the event of a fire and the The associated change in potential at point a becomes conductive, a large one flows Current between lines L1 and L2 through rectifiers D10, D5, thyristor S1 and Rectifier D8 so that the current detector in the signaling center issues a fire alarm signals.

During the functional test of fire detector A, a voltage reverse polarity, as marked with symbol t, to the signal lines L1 and L2 applied, so that now line L2 positive and lead L1 is negative. By the current flowing from line L2 to line L1 through the current stabilizer from rectifier Dll, capacitor C1, resistor R3, field effect transistor T2 and Resistance R2 flows, the capacitor C1 charges up. As long as the fire detection part Al. is in the normal state, on the other hand, the resistance is fll3 across the rectifier D7 and D9 connected in parallel to resistor R10 and resistor R12 via the rectifier D9 in parallel with resistor R11. This increases the potential at the emitter b of the transistor T1 on, transistor T1 and thyristor S1 become conductive, and the series connection of Rectifier Dll, capacitor C1 and resistor R3 are short-circuited. In the following the charge of the capacitor C1 is interrupted and field effect transistor T3 and Thyristor S2 do not switch to continuity.

Therefore flows between the lines L1 and L2 when the thyristor is conducting S1 a current through rectifier D7, thyristor s1, rectifier DG and the current stabilizer from field effect transistor T2 and resistor R2. So in this case the current is limited in such a way that the current detector in the signal center does not respond. However, when the fire detection part Al does not work properly, the thyristor becomes S1 not conductive.

As soon as the charging voltage of the capacitor C1 then exceeds the sum of the threshold voltage of the field effect transistor T3 and the Zener voltage of the Zener diode D1 after a certain time Charge / has exceeded, the field effect transistor T3 and thyristor S2 become conductive, so that a relatively large current flows through the signal lines Ll and L2, which causes the current detector in the signal center to respond and signals a fault.

The circuit of Figure 3 corresponds to that shown in Figure Ib Block diagram. If the rectifier DlO in the current limiting circuit 3 'by a A similar current stabilizer like the one in parallel to the rectifier D12 was replaced is, however, with opposite current passage riclatuny, this circuit can can be converted into a circuit analogous to FIG.

The circuit diagram shown in Figure 4 is a simplified version the circuit of Figure 3. The changes are that the rectifier D6 arranged directly between the current limiting circuit 3 'and the signal line L1 is, so that it also fulfills the task of the rectifier Dli, which is omitted can. Furthermore, the anode of the rectifier D5 is offset with the cathode of the Rectifier D6 connected, so the rectifier D5 additionally does the job of the rectifier D10 takes over, which also like the resistor R12 can be omitted. Otherwise, the structure and function of the circuit are correct FIG. 4 corresponds to the example according to FIG.

In the embodiments described so far, there was a fire alarm in each A, a fire detector part Al and an associated malfunction detection part A2 are provided. However, the fault monitoring part A2, except for the current limiting circuit, can also be used instead 3 or 3 'in the individual fire detectors by one for several connected in parallel Common fault detection part, e.g. by a relay unit, for the reason that the fault detection parts of the individual detectors are identical Fault signal in the signal lines L1 and L2 both in the case of a response Generate fire alarms as well as the response of several fire alarms.

For this purpose, in the circuits according to FIGS. 2 to 4, in the fault detection part A2 is the connection between point e at the input of the current stabilizer and point f can be interrupted on one side of the resistor R3 and a rectifier D12 between point f and point c in line L1 'in fire detector part Al as shown in dashed lines.

In the circuit diagrams according to Figures 2 to 4, the fire sensor contains as actual sensing element is a thermistor Th, its resistance with temperature decreases, in series with a fixed resistor RO and a transistor T1, which is derived from the potential at junction a of thermistor Th and resistor R0 is controlled. However, the invention is not limited to this arrangement, but rather can be used in the same way for other fire sensor elements based on other fire phenomena react, e.g. to smoke. The sensor element can be used as a smoke-sensitive, outer ionization chamber be formed, the ionization current decreases when smoke penetrates, and instead of the resistance R0, a Smoke-insensitive, e.g. a closed reference ionization chamber, and instead a field effect transistor can be provided for a normal transistor.

The examples described show that there is a fire alarm system Can create a relatively simple construction, which a functional check of connected fire alarms, with an inoperative detector safe in the signal center even with many detectors connected in parallel and can be easily ascertained during such a function check.

Claims (9)

CLAIMS 1, fire alarm system with a pair of signal lines in parallel Fire detectors connected to a signal center, the signal central one Test signal to check the functionality of the connected fire detectors able to deliver to the signal lines, characterized in that the fire alarm have a circuit (6) responsive to the test signal, of which the fire sensor (1, 2) of the fire detector is actuated, and that a current-limiting device in each fire detector (3, 3 ') is provided, which in the signal lines (L1, L2) when actuated Fire sensor flows current, at least during the functional check the fire detector, limited to a specified value, and that it continues to be a fault signal transmitter (5) is provided, which generates a fault signal in the signal lines if a fire sensor within a specified delay time after the test signal has been issued has not responded and that the signal center (B) also has a device (7 ', 8) as proof of this by one when checking the functionality addressed fire detector has triggered fault signal. 2. Fire alarm systems. according to claim 1, characterized in that a time switch device (4) is provided which reacts to the test signal responsive circuit (6) is actuated, which the fault signal generator (5) after After a predetermined delay time is actuated, but the actuation blocked when the fire sensor (2) responds. 3. Fire alarm system according to claim 2, characterized in that the current limiting device (3 ') from the circuit responsive to the test signal (6) is controlled in such a way that it can only be used during the functional check is in function. 4. Fire alarm system according to one of claims 1 - 3, characterized in that that the test signal consists of an increase in voltage. 5. Fire alarm system according to claim 4, characterized in that the signal center separate current detectors (7, 8) for the signaling of a Has alarm current and a fault current. 6. Fire alarm system according to claim 4 or 5, characterized in that that the fire alarms have Zener diodes (D2, D4), which at normal operating voltage are non-conductive, but if the voltage increases during the checking process become conductive and thereby cause the fire sensor (Tl, Sl) to respond, a timer (C1, R3) and, if necessary, also the current limiting circuit (T2, Put R2) into operation. 7. Fire alarm system according to one of claims 1 - 3, characterized in that that in the signal center a device (11) for reversing the voltage polarity on the lines (L1, L2) while checking the functionality of the fire alarm is provided. 8. Fire alarm system according to claim 7, characterized in that the fire detectors contain anti-parallel diode pairs (D5, D6 D7, D8) through which in the event of voltage reversal, the resistance ratios are changed so that the fire sensor responds and a timer is put into operation and, if applicable, the voltage limiter is put into operation. 9. Fire alarm system according to one of claims 2 - 8, characterized in that that the timer has a capacitor (C1) that can be charged via a resistor (R3) has, by the state of charge of the fault signal generator is controlled and whose Charging is interrupted when the fire sensor responds.