GB1575484A

GB1575484A - Coupled fire extinguishing and guarding systems

Info

Publication number: GB1575484A
Application number: GB1418978A
Authority: GB
Original assignee: SECURITY PATROLS CO Ltd
Current assignee: SECURITY PATROLS CO Ltd
Priority date: 1978-03-30
Filing date: 1978-04-11
Publication date: 1980-09-24
Also published as: JPS5637599B2; AU3573678A; AU522511B2; JPS54139397A

Description

(54) COUPLED FIRE EXTINGUISHING AND GUARDING SYSTEMS (71) We, SECURITY PATROLS CO., LTD., a Company organized and existing under the laws of Japan of 9-13, Akasaka 1-chome, Minato-ku, Tokyo, Japan, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a fire extinguishing system coupled to a guarding system for protecting the same region as covered by the fire extinguishing system.

A fire extinguishing system has been proposed wherein a fire sensor or sensors are arranged at a desired location or locations within the region to be protected by the system, for example at a position or positions in the ceiling of a room defining the region. A nozzle or nozzles of a fire extinguisher or fire extinguishers capable of discharging a fire extinguishing medium, such as fire extinguishing gas, are placed at a desired location or locations within the region. As a result, in response to a fire signal from the fire sensors, the fire extinguishing medium can be caused to discharge from the nozzles or the fire extinguishers into the region to effect automatic extinguishing of the fire.

It can be easily understood that, if the sensitivity of the fire sensors cooperating with fire extinguishers disposed in the desired region for protection is high, fire extinguishing can be accomplished more effectively. Consequently, it is always desired to use fire sensors having high sensitivity, such as a smoke detector or a heat detector, which satisfy the above-mentioned requirement. However this type of sensor has a drawback in that the sensor may issue its output signal often in accordance with factors other than fire, because of its high sensitivity. For example, some smoke sensors issue their signals in a case where a person smokes a cigarette in close proximity to a position where the above-mentioned smoke sensor is disposed. In addition, some heat sensors issue their signals in a case where the room temperature is abruptly changed due to the start of an air conditioner.In the above-mentioned cases, a fire sensor transmits an erroneous signal to a means for actuating the fire extinguishing system, so that the fire extinguishing system is operated in response to such erroneous signals and the fire extinguishing gas is discharged from the fire extinguisher or fire extinguishers.

According to investigations conducted by the inventor of the present application, regarding the frequency of the above-mentioned erroneous signal issued from a fire sensor or fire sensors utilized for the conventional fire alarm system, it was found that such erroneous signals have been more frequently issued during business hours than during non-business hours in places where such a fire alarm system is installed. It is the inventor's understanding that such frequent issuing of an erroneous signal from a fire sensor or sensors is mainly due to the very high sensitivity of each fire sensor which can be actuated by such phenomenon as smoking in a place in close proximity to the fire sensor or the possible rapid elevation of the room temperature which is created by the starting of an air conditioning apparatus utilized for heating the room.

If the above-mentioned fire sensor or fire sensors, having high sensitivity, are utilized for the above-mentioned automatic fire extinguishing system utilizing at least one fire extinguisher which is capable of discharging extinguishing gas, in response to the signal issued from the fire sensor, and if such gas is asphyxiating, such as carbon dioxide gas, any person in a place where such gas is discharged from the fire extinguisher or fire extinguishers, could be subjected to an injury which could be fatal.

To prevent the occurrance of accidents caused by the discharge of asphyxiating gas from a fire extinguisher or extinguishers due to the above-mentioned erroneous signal, a fire extinguishing system has been utilized in which the fire sensor or sensors thereof do not have the above-mentioned high sensitivity for detection but are provided with a reliable function of being capable of detecting only heat. In this type of fire extinguishing system, the fire extinguisher, or extinguishers, is so designed as to be operatively connected to the fire sensors only when no people is present within the region covered by the system.

In the conventional fire extinguishing systems utilizing fire-sensor or sensors having high sensitivity, such a switch change means is employed that the system can be manually switched from a standby condition to an automatic operating condition in which it responds to any signals issued from the fire sensor or sensors, during the time when no person is in the fire protecting region; while in the standby condition the system is maintained in a manually operable condition during the time person is in the fire detecting region.

Consequently, if such a fire extinguishing system is employed in an office building, it is necessary to operate the above-mentioned switch change means each time the system is changed from the standby or automatic operating condition, in accordance with whether a person is in the fire protecting region or not. Therefore, if the above-mentioned switch change means is applied to the fire extinguishing system, since no person is in the fire detecting region when the fire extinguishing system is in an automatic operating condition, the possibility of erroneous signals being issued from the fire sensor or fire sensors due to the above-mentioned causes such as the smoking of a cigarette or the abrupt elevation of the room temperature at the time of starting the air conditioning can be remarkably reduced.

However, the above-mentioned switch change means is very complicated and troublesome, because it is strictly required to confirm whether some person is still in the fire protecting region or not. Furthermore, if a fire sensor or sensors having high sensitivity is utilized, this switch change means is also very dangerous, because if a person enters into the fire protecting region after the fire extinguishing system is changed from the standby condition to the automatic operating condition, there is no way the person can be protected from possible injury due to a possible erroneous signal being issued from the fire sensor or sensors.

On the other hand, if a fire sensor, or sensors, having comparatively lower sensitivity is adopted so as to prevent the above-mentioned possible troubles, another serious problem due to the possible delayed detection of a fire can not be prevented.

According to the present invention, there is provided a fire extinguishing system coupled with a guarding system for protecting the same region as covered by the fire extinguishing system, the guarding system having at least one intrusion detector at a desired location in said region, and the fire extinguishing means having at least one fire sensor in the region and at least one fire extinguishing device, and the coupled fire extinguishing and guarding sytems having automatic control circuitry arranged to actuate the or each fire extinguishing device automatically in response to the or one of the fire sensors detecting fire, means inhibiting said automatic actuation response of the control circuitry when the or one of the intrusion detectors detects an intruder, and manually operable actuation means arranged for manual actuation of the or each fire extinguishing device in the absence of automatic actuation.

With this arrangement it is possible to use fire sensors with high sensitivity, and yet reduce the problems of erroneous signals being issued by the fire sensors.

Since several types of fire sensors having high sensitivity are known, it is not difficult to find a suitable fire sensor for the present invention. Based on the results of research conducted by the inventor, it was confirmed that, if a so-called automatic guarding system for protecting a specified region, such as office buildings, and warehouses, from burglary is coupled with a fire extinguishing system as described above, spurious operation of the fire extinguishing system can be much reduced.

If such an automatic guarding system is combined with the fire extinguishing system, the presence of people in the fire protecting region is always detected and, the fire extinguishing system can be automatically switched from the automatic operating mode to the manual operation mode; or in the case where all people leave the region from the manual mode to the automatic operating mode.

In a suitable guarding system, one or more intrusion detectors are arranged in appropriate locations within the guarding region, and a signal issued from at least one of these detectors is transmitted to a remote guard control center for monitoring any intrusion into the region. This type of guarding system is typically so designed that it may be switched to a "set condition" when no personnel are in the region, while it may be switched to an "off condition" when personnel are legitimately in the region. Only during the period when the guard system is in the "set condition", is the response of the intrusion detectors transmitted to the guard control center as a warning signal.

Thus, conveniently, the present coupled fire extinguishing and guarding systems include switching means arranged for selectively switching the guarding system between a set condition in which the guarding system is operative to indicate the presence of any intruders in the region by generating an appropriate warning signal and an off condition in which the generation of the warning signal is inhibited, said means inhibiting said automatic actuation response of the control circuitry being arranged for inhibiting said automatic actuation response also when the switching means is in the off condition.

Further the coupled systems may include a mode selection switch manually operable between one mode in which the inhibiting means inhibits said automatic actuation response only when the or one of the intrusion detectors detects an intruder, and a second mode in which the inhibiting means inhibits said response also when the switching means is in the off condition, the intrusion detectors remaining responsive to the presence of an intruder whether the switching means is in the set or off conditions.

Examples of the invention are now described with reference to the accompanying drawings, in which: Figure 1 is a graphical representation of the relationship between the frequency of erroneous signals issued from fire sensors and the time of day for a conventional fire alarm system, as investigated for 30 days, in July, 1977; Figure 2 is a block diagram of a fire extinguishing and intruder alarm system embodying the present invention; Figure 3 is a diagrammatical representation of a logic circuit in the fire extinguishing system shown in Figure 2; and Figures 4 and 5 are diagrammatical representations of logic circuits in modified fire extinguishing systems embodying the present invention.

As illustrated in Figure 1, investigations conducted by the inventors of the present application regarding the erroneous signals issued from fire sensors of 4000 conventional fire alarm systems, in the Tokyo area for 30 days in July, 1977 show clearly that the frequency of erroneous signals from the fire sensors of these conventional alarm systems is higher during business hours.

Figure 2 is a block diagram of a fire extinguishing system combined with an automatic guarding system, embodying the present invention. Referring to Figure 2, a plurality of intrusion detectors 30 are installed in appropriate locations in a specified region 10 in a building covered by a guarding system, and a plurality of fire sensors 25 are also disposed at appropriate locations in the region 10, while a monitor device 21 is provided in a control center 28 remote from the above-mentioned building. Signals issued by any of the intrusion detectors 30 and the fire sensors 25 are converted by a warning signal transmitter 23 for transmission via a transmission line 22 to the monitor 21. A switching device 24 is disposed so as to cooperate with the warning signal transmitter 23.The automatic guarding system can be set in an operative guarding condition by operating the switching device 24 when the above-mentioned region 10 must be protected by the system, for example, when nobody is supposed to be in the region 10 such as at night. On the other hand, when there are people legitimately in the region 10 so that the guarding system should not be operative, the guarding system can be put in an inoperative or stand-by condition also by operating the switching device 24. In addition, there is provided a manual actuation switch 20 which is connected to fire extinguisher control system 40.

In the above-mentioned embodiment, the fire extinguishers of the kind disclosed in Swiss Patent No. 597,875 are utilized. Therefore, no detailed explanation of the fire extinguishers is given herein.

The construction, operation and function of the above-mentioned fire extinguishing system of Figure 1 is explained in more detail with reference to Figures 2 and 3, and Tables 1-1, 1-2, 1-3, 1-4 and 1-5.

The switching device 24 is provided with an interface 1 which is an input unit for receiving specific magnetic cards, and a combination of decimal keys on a keyboard or a key switch.

The interface 1 is capable of issuing an identification signal upon identifying a specified input. For the interface 1, a conventional interface unit may be adopted. The switching device 24 is further provided with a transistor 2 which is connected to the interface 1 and earth. The collector of the transistor 2 is connected to a power source (5V) via a resistor 3 and also connected to an invertor 26. When the input unit is actuated by, for example, inserting a specific magnetic card, the interface 1 issues a signal indicating that the guarding system is to be released from its operative guarding condition. If the specific magnetic card is again inserted into the input unit, the interface 1 issues a signal to indicate that the guarding system is to be set in its guarding condition.For the sake of simplifying the following explanation, the above-mentioned released condition of the guarding system is hereinafter referred to as the "off condition" and the above-mentioned set condition of the guarding system is hereinafter referred to as "set condition".

In the switching device 24, when the interface 1 issues a "set condition" signal, the transistor 2 is turned on. In this condition, the collector voltage is changed from 5 volts to zero volt. On the other hand, if the interface 1 issues an off signal, the transistor 2 is turned off so that the voltage between the collector of the transistor 2 and the earth becomes 5 volts. For the sake of simplifying the following explanation, the voltage condition of 5 volts is hereinafter referred to as "H" and the voltage condition of zero volt is hereinafter referred to as "L". That is, when the switching device 24 is in the set condition, the collector voltage of the transistor 2 is L, and in the off condition of the device 24, the collector voltage of the transistor 2 is H. The potential at the output of the inverter 26 becomes H in the set condition, and L in the off condition.

For the intruder sensors 30, any suitable sensor can be used effectively, such as the intruder sensor disclosed in Japanese Laid-open Specification Serial No. 88197/1976, which is an optical sensor capable of detecting the radiation energy from a human body, or a known electro-mechanical intrusion sensor disposed at an entrance door of a room. In the embodiment shown in Figure 3, for the sake of an easy understanding of the present invention, the intrusion sensor 30 is represented by a simple on-off switch which will be automatically opened when the sensor 30 detects an intruder. The intrusion sensors 30 are connected in series between the power source (5V), and earth by way of a resistor 4, in series.When one of the sensor 30 is actuated, that is, the on-off switch thereof is opened, the potential at the junction point of one of the sensors 30 and the resistor 4 is changed from H to L.

For the fire sensors 25, it is generally desirable to use a fire sensor having a high sensitivity. For this purpose, a fire sensor for detecting heat radiation or for detecting flame, having high sensitivity can be used. For the sake of simplifying the explanation, in the embodiment shown in Figures 2 and 3, the fire sensors 25 are also represented by a simple on-off switch which will be turned on when the sensor 25 detects fire. These fire sensors 25 are connected in parallel between the power supply source (5V) and earth by way of a resistor 5, and when one of the sensor 25 detects fire, the on-off switch thereof is closed so that the potential at the junction point of the sensors 25 and the resistor 5 is changed from the L to H.

The warning signal transmitter 23 is provided with electric circuits and elements as shown in Figure 3. That is, the transmitter 23 receives signals from the intrusion detectors 30 and the fire sensors 25, and, in both conditions of the switching device 24, that is in the set condition or the off condition of the device 24, the transmitter 23 combines the signals from the intrusion sensors 30 and the fire sensors 25 and creates desired warning signals thereof by means of an encode circuit 9, so that the warning signals are transmitted to the monitor 21 by way of the transmission line 22. Thus, when one of the intrusion detectors 30 detects an intruder so that the potential at the junction of the detector 30 and the resistor 4 is changed from H to L the potential at the output of an invertor 6 is inverted from L to H and the output of the invertor 6 is applied to a NAND circuit 7.If the switching device 24 is in the set condition, the potential at the output of the invertor 26 is H. Since the potential at -the output of the invertor 6 is H, the potential at the output of the NAND circuit 7 is changed from H to L. That is, only when one of the intrusion sensors 30 is actuated and the switching device 24 is in the set condition does the potential at the output of the NAND circuit 7 become L. This output signal is encoded by the encode circuit 9 and transmitted as an intrusion warning signal via the transmission line 22 to the monitor 21 in the control centre 28.

When one of the fire sensors 25 is activated, the potential at the output of an invertor 8 becomes L and the output of the invertor 8 is subject to encoding by the encode circuit 9 for transmission as a fire warning signal to the monitor 21. The fire extinguisher control system 40 is provided with a NAND circuit 10, another NAND circuit 12, and NOR circuits 15 and 16, inverters 11, 13 and 14, a transistor 17, an actuator 18 for actuating a control valve (not shown) for each fire extinguisher, and a resistor 19 which is connected in series between the actuation switch 20 and earth. When the switching device 24 is in the set condition, and the intrusion sensors 30 are all closed, both potentials at the inputs of the NAND circuit 10 are H so that the potential at the output thereof will be L. Therefore, the potential at the output of the invertor 11 and one input of the NAND circuit 12 is H. When one of the fire sensors 25 is actuated, the potential at the other input of the NAND circuit 12 becomes H, so that the output thereof will become L. This output signal is inverted to be "H" by an inverter 13 and applied to one input of the NOR circuit 16. If the actuation switch 20 for manually actuating the fire extinguisher control system 40 is not closed, the potential at the input of the inverter 14 is maintained L. Therefore, the potential at the output of this inverter 14 is H and this output is applied to one input of the NOR circuit 15. As the other input of the NOR circuit 15 is connected to the output of the inverter 11, the second input of the NOR circuit 15 is also H.Thus, the potential of the output of this NOR circuit 15 is L so that the potentials of the inputs of the NOR circuit 16 will be H and L respectively. Therefore, the potential of the output of this NOR circuit 16 becomes L so that the transistor 17 is turned on and, consequently, the fire extinguisher actuator 18 is actuated. To actuate the actuator 18, the output level of the NOR circuit 16 must be L. Thus, the fire extinguisher control system 40 is automatically actuated without closing the actuation switch 20, only if one of the fire sensors 25 is actuated while the switching device 24 is in the set condition and none of the intrusion sensors 30 is operated.That is, the fire extinguisher control system 40 can operate automatically in response to one of the fire sensors 25 detecting a fire, only while none of the intrusion sensors 30 detects an intruder, i.e. when there is no one in the guarded region, and so long as the guard system is in the set condition.

When there are people in the guarded region, either the switching device 24 is put in the off condition, or one of the intrusion sensors 30 will operate, or both. Then the output of the inverter 11 and hence one input of the NOR circuit 15 is L. The fire extinguisher system can then be actuated manually only by closing the actuation switch 20 so that the output of the inverter 14 and hence the other input of the NOR circuit 15 becomes L. Since the output of the inverter 11 is already L, the output of the NOR circuit 15 becomes H so that the output of the NOR circuit 16 becomes L, turning on transistor 17 and actuating the actuator 18.

The following tables show the output potentials of each element in the guarding system and the fire extinguishing system, for various conditions of the switching device 24, the intrusion detector 30 and the fire sensors 25.

TABLE 1-1 Elements Output Potential Note (reference numeral) High Low Switching device (24) 0 in the set condition Intrusion detector (30) 0 in the watching condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the off condition Logic circuits Inverter (26) 0 NAND circuit (10) 0 Inverter (11) 0 NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned on Fire extinguisher in the actuating actuator (18) condition Note: The fire extinguishing system can be automatically actuated.

TABLE 1-2 Elements Output Potential Note (reference numeral) High Low Switching device (24) 0 in the set condition Intrusion detector (30) 0 detects abnormal condition Fire sensor (25) O detects fire Actuation switch (20) O in the off condition Logic circuits Inverter (26) 0 NAND circuit (19) 0 Inverter (11) 0 NAND circuit (12) O Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) O Transistor (17) turned off Actuator (18) does not actuate Note:- The fire extinguishing system cannot be automatically actuated.

TABLE 1-3 Elements Output Potential Note (reference numeral) High Low Switching device (24) 0 in the off condition Intrusion detector (30) 0 in the watching condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the off condition Logic circuits Inverter (26) 0 NAND circuit (10) 0 Inverter (11) 0 NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned off Fire extinguisher does not actuate actuator (18) Note: The fire extinguishing system can not be automatically actuated.

TABLE 1-4 Elements Output Potential Note (reference numeral) High Low Switching device (24) 0 in the off condition Intrusion detector (30) 0 detects abnormal condition Fire sensor (25) 0 does not detect fire Actuation Switch (20) 0 in the set condition Logic circuit Output potential of the logic circuit Inverter (26) 0 NAND circuit (10) 0 Inverter (11) 0 NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned on Fire extinguisher in the actuating actuator (18) condition Note: The fire extinguishing system can be manually actuated.

TABLE 1-5 Elements Output Potential Note (reference numeral) High Low Switching device (24) 0 in the off condition Intrusion detector (30) 0 detects abnormal condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the set condition Logic circuit Output potential of the logic circuit Inverter (26) 0 NAND circuit (10) 0 Inverter (11) 0 NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned on Fire extinguisher in the actuating actuator (18) condition Note: The fire extinguishing system can be manually actuated.

TABLE 1-6 Elements Output Potential Note (reference numeral) High Low Switching device (24) 0 in the off condition Intrusion detector (30) O detects abnormal condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the off condition Logic circuit Output potential of the logic circuit Inverter (26) 0 NAND circuit (10) 0 Inverter (11) 0 NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned off Fire extinguisher does not actuate actuator (18) Note: The fire extinguishing system can not be actuated without operating the actuation switch (20).

Table 1-1 shows the logic conditions when the guarding system is in the set condition, there is no one in the protected region and the fire sensors detect fire. Only then, can the fire extinguishing system be actuated automatically.

Table 1-2 shows the logic conditions when the guarding system is set but the intrusion detectors detect an intruder, in which case automatic actuation of the fire extinguishing system is inhibited and it can only be operated manually by the actuation switch 20.

Tables 1-3 to 1-6 show various possible logic conditions when the guarding system is in the off condition, whereupon the fire extinguishing system can only be operated manually by the actuation switch 20.

Thus, table 1-3 shows the logic conditions when the fire sensors detect fire, there is no one in the protected region and the actuation switch 20 is off. Table 1-4 shows the conditions when the fire sensors do not indicate a fire and the intrusion detectors show an intruder, but the actuation switch 20 is closed to actuate the fire extinguishers. Table 1-5 shows conditions under the same circumstances as Table 1-4 except that the fire sensors do detect fire. Table 1-6 shows conditions under the same circumstances as Table 1-5 except that the actuation switch 20 is off.

The circumstances of Table 1-5 may arise if there is an outbreak of fire which has been noticed at the control centre and a fireman or other personnel enters the protected region and operates the actuation switch so to actuate the fire extinguishers.

Figure 4 shows another embodiment of logic circuit for the fire extinguishing and guarding system, which is quite similar to that shown in Figure 3, except that a system selection switch 27 is additionally inserted in the circuit. With the system selection switch 27 in the position shown in Figure 4, the circuit operates exactly as the circuit of Figure 3.

However, with switch 27 in the set condition it connects the signal from the intrusion detectors 30 directly to the input of NAND circuit 12. Then, the circuit in Figure 4 operates in the same manner as that in Figure 3, except that automatic actuation of the fire extinguishers is not inhibited by putting the switching circuit 24 in the off condition.

Automatic operation is inhibited only in response to the intrusion detectors 30 detecting an intruder. The various system conditions when the switch 27 is in the set condition are illustrated in the following Tables 2-1 fo 2-4.

TABLE 2-1 Elements Output Potential Note (reference numeral) High Low Intrusion detector (30) 0 does not detect abnormal condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the set-off condition Logic circuit NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned on Fire extinguisher in the actuating actuator (18) condition TABLE 2-2 Elements Output Potential Note (reference numeral) High Low Intrusion detector (30) 0 detects abnormal condition Fire sensor (25) 0 does not detect fire Actuation switch (20) 0 in the set condition Logic circuit NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned on Fire extinguisher in the actuating actuator (18) condition TABLE 2-3 Elements Output Potential Note (reference numeral) High Low Intrusion detector (30) 0 detects abnormal condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the set condition Logic circuit NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned on Fire extinguisher in the actuating actuator (18) condition TABLE 2-4 Elements Output Potential Note (reference numeral) High Low Intrusion detector (30) 0 detects abnormal condition Fire sensor (25) 0 detects fire Actuation switch (20) 0 in the set-off condition Logic circuit NAND circuit (12) 0 Inverter (13) 0 Inverter (14) 0 NOR circuit (15) 0 NOR circuit (16) 0 Transistor (17) turned off Fire extinguisher in the non-actuating actuator (18) condition Under the conditions shown in Table 2-1, when there is no one in the protected region, the fire extinguishing system is actuated automatically if a fire sensor 25 detects an outbreak of fire.

Table 2-2 shows the case where, although the fire sensors 25 are not actuated for some reason, a fire breakout is found by some person and he operates the actuation switch 20, to effect the operation of the fire extinguishers.

Table 2-4 shows the case where, although the fire sensor 25 detects an outbreak of fire while there are people in the protecting region, the fire extinguisher is not operated.

Table 2-3 shows the case where, under the conditions shown in Table 2-4, by operating the actuation switch 20, the fire extinguisher is actuated.

Figure 5 illustrates another embodiment of logic circuit for the fire extinguishing and guarding system which can operate solely in the manner of the circuit of Figure 4 when the system switch 27 is in the set condition. Thus, when the switching device 24 is in the set condition, a warning signal from the intrusion sensors 30 or fire sensors 25 is transmitted along the transmission line 22 to the monitor 21 in the control centre 28 and the monitor 21 indicates such signals. When one of the intrusion sensors 30 is open, the extinguisher will only be actuated if the actuation switch 20 is operated. On the other hand, when one of the fire sensors 25 detects an outbreak of fire while the intrusion sensors 30 do not detect any abnormal condition, the fire extinguisher can be actuated automatically.This embodiment of the fire extinguishing system is especially convenient to be switched to "automatic" mode even for a short desired time if the system is installed in a laboratory or the like where only a small number of persons work.

Many further modifications and variations can be made to the examples of the present invention described above, for example, by providing additional usual accessories, such as an alarm buzzer or indication lamp which may be included guarding and fire extinguishing systems.

WHAT WE CLAIM IS: 1. A fire extinguishing system coupled with a guarding system for protecting the same region as covered by the fire extinguishing system, the guarding system having at least one intrusion detector at a desired location in said region, and the fire extinguishing means having at least one fire sensor in the region and at least one fire extinguishing device, and the coupled fire extinguishing and guarding systems having automatic control circuitry arranged to actuate the or each fire extinguishing device automatically in response to the or one of the fire sensors detecting fire, means inhibiting said automatic actuation response of the control circuitry when the or one of the intrusion detectors detects an intruder, and manually operable actuation means arranged for manual actuation of the or each fire extinguishing device in the absence of automatic actuation.

2. Coupled fire extinguishing and guarding systems as claimed in claim 1 and including switching means arranged for selectively switching the guarding system between a set condition in which the guarding system is operative to indicate the presence of any intruders in the region by generating an appropriate warning signal and an off condition in which the generation of the warning signal is inhibited, said means inhibiting said automatic actuation response of the control circuitry being arranged for inhibiting said automatic actuation response also when the switching means is in the off condition.

3. Coupled fire extinguishing and guarding systems as claimed in claim 2 wherein the switching means has an interface arranged for identifying and responding to identification elements.

4. Coupled fire extinguishing and guarding systems as claimed in claim 2 or claim 3 wherein the switching means is an electro-mechanical locking key means.

5. Coupled fire extinguishing and guarding systems as claimed in any of claims 2 to 4 and including a mode selection switch manually operable between one mode in which the inhibiting means inhibits said automatic actuation response only when the or one of the intrusion detectors detects an intruder, and a second mode in which the inhibiting means inhibits said response also when the switching means is in the off condition, the intrusion detectors remaining responsive to the presence of an intruder whether the switching means is in the set or off conditions.

6. Coupled fire extinguishing and guarding systems as claimed in any preceding claim including remotely situated monitoring means and a warning signal transmitter arranged for sending respective warning signals to the monitoring means in response to detection by the systems of fire, an intruder, or both, the -monitoring means indicating the detection of fire or an intruder or both in response to said respective warning signals.

7. Coupled fire extinguishing and guarding systems as claimed in claim 6 and including an alarm arranged to produce an alarm signal in response to receipt by said monitoring means of a warning signal.

8. Coupled fire extinguishing and guarding systems as claimed in any preceding claim wherein the or at least one of the fire sensors is a smoke sensor.

9. Coupled fire extinguishing and guarding systems as claimed in any of claims 1 to 7

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. system switch 27 is in the set condition. Thus, when the switching device 24 is in the set condition, a warning signal from the intrusion sensors 30 or fire sensors 25 is transmitted along the transmission line 22 to the monitor 21 in the control centre 28 and the monitor 21 indicates such signals. When one of the intrusion sensors 30 is open, the extinguisher will only be actuated if the actuation switch 20 is operated. On the other hand, when one of the fire sensors 25 detects an outbreak of fire while the intrusion sensors 30 do not detect any abnormal condition, the fire extinguisher can be actuated automatically.This embodiment of the fire extinguishing system is especially convenient to be switched to "automatic" mode even for a short desired time if the system is installed in a laboratory or the like where only a small number of persons work. Many further modifications and variations can be made to the examples of the present invention described above, for example, by providing additional usual accessories, such as an alarm buzzer or indication lamp which may be included guarding and fire extinguishing systems. WHAT WE CLAIM IS:

1. A fire extinguishing system coupled with a guarding system for protecting the same region as covered by the fire extinguishing system, the guarding system having at least one intrusion detector at a desired location in said region, and the fire extinguishing means having at least one fire sensor in the region and at least one fire extinguishing device, and the coupled fire extinguishing and guarding systems having automatic control circuitry arranged to actuate the or each fire extinguishing device automatically in response to the or one of the fire sensors detecting fire, means inhibiting said automatic actuation response of the control circuitry when the or one of the intrusion detectors detects an intruder, and manually operable actuation means arranged for manual actuation of the or each fire extinguishing device in the absence of automatic actuation.

wherein the or at least one of the fire sensors is a flame sensor.

10. Coupled fire extinguishing and guarding systems as claimed in any of claims 1 to 7 wherein the or at least one of the fire sensors is a heat sensor.

11. A fire extinguishing system coupled to a guarding system substantially as hereinbefore described with reference to and as illustrated in Figures 2 and 3, or Figures 2 and 3 as modified by Figure 4 or Figure 5 of the accompanying drawings.