GB2197740A - Incident warning system - Google Patents

Abstract

Monitoring apparatus for an incident warning system which includes an audible or visual alarm device 1, 2 and a unit 5 for operating the device in response to detection of an incident. The monitoring apparatus comprises a transducer 7, 21 associated with each alarm device and located to receive an audible signal or alarm signal from the alarm device; and a system 11 responsive to failure to detect such a signal of at least a predetermined amplitude to give warning of incorrect operation of the device. <IMAGE>

Description

INCIDENT WARNING SYSTEM This invention relates to monitoring apparatus for an incident warning system including one or more audible or visual alarm devices, which apparatus is able to carry out checks on the integrity of the alarm devices, and to an incident warning system including such monitoring apparatus.

Incident warning systems (IWS) include detectors for detecting the existence of intruders, fire or other hazardous situations, and audible and/or visual alarm devices for giving warning of the detected incident, either in the area of the incident or at a remote location.

Such audible alarm devices may be electromechanical bells or gongs, electro-pneumatic sirens, electromagnetic sounders, piezo-electric devices, moving-coil or movingiron loudspeakers, or any other device which is capable of generating a warning sound in the event of an incident endangering the safety of people or property.

Audible warning systems may be divided into two types, namely those giving non-intelligent warning and those giving intelligent warning.

Non-intelligent warning occurs when a gong, bell, siren or like device is used to announce an incident.

Certain actions may be taken by personnel involved, depending on simple coding of the warning tone. For example, a continuous tone might signal immediate evacuation of a building; a broken or warbling tone warning of a pending problem; and an interrupted tone merely announcing testing of the system. Non-intelligent warning requires prior knowledge of the coded sound used, by all personnel involved.

Intelligent warning systems are capable of providing both warning tones and clear speech reproduction. The spoken message can convey intelligent information to all parts of a building or open site. Evacuation directions may be given, and fixed messages in a variety of languages and warning tones can be broadcast to personnel to ensure that maximum safety procedures are followed in the event of an incident.

Incident warning systems are subject to stringent self-test and monitoring routines to ensure that they function continuously, or so that they signal to relevant personnel (Fire Officer, Engineer etc.) when a fault occurs which would limit the degree of warning which would be given in the event of an incident occurring. A monitor panel is usually arranged to indicate the status of various sections of the equipment and, if a fault occurs, this panel pinpoints the location of the fault, and any zone or area of protection which may be inadequately covered.

Instead of, or in addition to, audible alarm devices, visual alarm devices, such as continuouslyilluminated or flashing lights of various colours, may be used.

In prior systems, the audible or visual alarm devices have not come within the continuously-monitored part of the system. The alarm devices are usually unmonitored, or are checked periodically by a Fire Officer or other responsible person during a fire alarm test. In a large installation, located on many floors, this becomes difficult, if not impossible, and there is a risk of the warning system not covering the premises or area properly because of undetected faulty alarm devices.

Also the risk of human error comes into play, since the testing requires conscious decisions and responses from a human being, resulting in the possibility of the test not being carried out reliably.

It is an object of the present invention to provide an incident warning system in which the integrity of the alarm devices is tested by the system.

According to the invention there is provided monitoring apparatus for an incident warning system which includes at least one audible or visual alarm device and means to operate the device in response to detection of an incident, the apparatus comprising sensing means located to receive an audible signal or a light signal from the alarm device; and means responsive to failure to detect such signal of at least a predetermined amplitude to give warning of incorrect operation of the device.

Preferably the sensing means is frequency-dependent and detects whether the received signal includes a signal component of at least a predetermined amplitude at a predetermined frequency.

Preferably the sensing means includes means to generate a two-state digital output having one state in response to detection of said signal component and having the other state in response to failure to detect said signal component.

In respect of an intelligent alarm device, the sensing means preferably detects whether the received signal includes two components of predetermined amplitude at predetermined frequencies spaced apart in the frequency spectrum of the received signal.

The invention also relates to an incident warning system including the aforementioned monitoring apparatus.

Two embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Fig. 1 is a block schematic diagram of an incident warning system including a first embodiment of monitoring apparatus according to the invention; Fig. 2 is a curve showing the variation of acoustic output level with frequency of a typical sounder used as an audible alarm device; Fig. 3 is a curve similar to that of Fig. 2, but showing two test frequencies; Fig. 4 is a flowchart indicating the operation of the system; and, Figure 5 is a block diagram of a second embodiment of monitoring apparatus according to the invention.

Referring to Fig. 1 of the drawings, an incident warning system is shown as including two different types of audible alarm devices, namely an intelligent device 1, such as a bi-directional compression loudspeaker, and a non-intelligent device 2, such as an electromechanical bell or gong. Although one of each of these types of device is shown for the purpose of explanation, a practical system may include any number of devices of either type, or a mixture of the two types.

The device 1 is connected to a routing circuit 3 which is fed from a typically 100volt audio distribution system 4. The routing circuit can apply to the device 1 tones of predetermined frequency in response to detection of an incident by a detector 5, or can apply thereto speech signals from a message reproducer 6 in response to such incident detection.

In order to allow testing of the integrity of the device 1, a transducer 7 of appropriate characteristics is mounted at a strategic point in the sound field distribution pattern of the device. This point is found by calculation of the sound field radiation pattern and is confirmed by empirical measurement. When suitably placed as described, the transducer 7 will provide an electrical signal proportional to the sound pressure level generated by the device 1 over the rated frequency range of operation of the device.

The output of the transducer 7 is fed to a detection circuit 8 which can discriminate a particular frequency component of the signal from the transducer and can determine whether the amplitude of the component is of an expected level for the particular alarm device/transducer combination. The detection circuit 8 also includes means to provide a 2-state digital output signal having one state, for example a "high" or binary 1 state, if the amplitude is as expected, and the other state, for example a "low" or binary 0 state, if the amplitude is lower than expected. The frequency discriminator of the circuit 8 may be a phase lock loop decoder.

The 1 or 0 bit from the circuit 8 is fed to a digital interface 9, which is coupled, via a data highway 10, to computing means 11, which is preferably a microprocessor. The microprocessor is coupled to a visual display unit 12, a printer 13 and a disk drive 14.

The digital interface can be suitably addressed by the microprocessor so that the interface reports a change of state of the data bit from the circuit 8 from 0 to 1 or vice versa, or that there has been no change. The interface can supply a command signal to the routing circuit 3, over a line 15, to cause the circuit 3 to apply a test signal to the device 1, under the control of the microprocessor 11. The test signal is designed to test the intelligent sounder device 1 fully to ensure that the intelligence broadcasting function, i.e.

broadcasting of messages from the reproducer 6, can be properly effected by the device 1. Such a test signal may be, for example, a sine wave of frequency midway between the frequency limits of the device/transducer combination or, for higher-integrity applications, may comprise two sine waves with frequencies selected at the band limits of the device/transducer combination. In the latter case, the discriminator of the circuit 8 would comprise, for example, two phase lock loop comparators, the outputs of which are fed to a logical AND-gate (not shown) to provide an output only when both sine wave frequencies are detected at the appropriate levels. In this way a very high degree of performance monitoring is provided.

Furthermore, by monitoring the performance of the device 1 at two or more selected frequencies (or narrow frequency bands), and generating digital signals indicating the test results at the various frequencies, an encoded digital signal may be fed to the microprocessor 11 so that a degree of diagnostic information as to the likely cause or nature of a fault can be displayed on the VDU 12.

A typical curve of output sound level versus frequency (on a logarithmic scale) for an intelligent sounder device, such as the device 1, is shown in Fig. 2 of the drawings. In this case the test signal is a lkHz tone, i.e. at the geometric mean of the band. This tone would effectively stimulate the device 1 sufficiently to give adequate signalling of conformance to specification.

It is well know in the art that faults normally result in a reduction of mid-band output in a sounder. Fig. 3 shows a typical intelligent sounder response curve similar to Fig. 2 but with two test tones shown at 700hZ and 5kHz, respectively, i.e. one at each end of the frequency band. The detection circuit 8 would look for a correct output sound pressure level at each individual frequency.

The non-intelligent device 2 (Fig. 1) is energised by a driver circuit 16 which applies thereto a bell voltage from a supply 17 in response to a command signal which is fed over a line 18 by the detector 5 if an incident occurs. Alternatively, a test signal can be applied to the device 2, in response to a signal on a line 19 from a digital interface 20 which is coupled over the data highway 10 to the microprocessor 11. A transducer 21 receives the audible signal from the device 2, and feeds an analog signal to a detection circuit 22.

The circuit 22 operates in a similar manner to the detection circuit 8 to generate a two-state digital output, which is fed to the interface 20. For the nonintelligent device 2, the detection circuit 22 is so arranged, by component selection within the circuit, that when the device is subjected to a short pulse of the normal excitation, i.e. the excitation which would be applied in the event of. an incident occurring, the sound level is measured and reported to the microprocessor 11.

The pulse applied during this test is controlled by the microprocessor, via the interface 20.

The use of a frequency-selective detection circuit 22 would improve the sensitivity of the monitoring apparatus, and would also improve its ability to discriminate between the signal from the alarm device 2 and normal environmental sounds, thereby reducing the likelihood of false indications being generated.

However, the use of frequency-selective monitoring is not essential, particularly for non-intelligent devices.

The microprocessor 11 is programmed to address each digital interface on the ring data highway 10 by means of a fixed address binary code, sent serially along data/address lines 23. Each digital interface, when correctly addressed by the coded data on the data highway, responds by issuing an acknowledgement signal and a description of state signal, i.e. a signal indicating whether the output of the respective detection circuit is high or low or has just changed state. The microprocessor then accepts the data, acknowledges receipt and goes on to address the next digital interface. A password and other security features will normally be included in the microprocessor software to prevent unauthorised access to the system.

By the end of a test sequence, the microprocessor 11 will typically have recorded the number and identity of interfaces present on the data highway, and the current state and the last state of the output of each detection circuit. Up to 255 interfaces may typically be connected to one ring data highway and each will be interrogated on a regular basis. At a prearranged test time, or at any time under operator control, the microprocessor 11 addresses each digital interface to enable the circuits 3 and 16, to receive the response of the detection circuits, and to acknowledge receipt of the response Access to the interfaces 9 and 20 and other interfaces in the system is effected sequentially in ascending order of address code.Each test of each sounder device may typically take 0.5 to 4 seconds, the microprocessor software being set up to repeat any test which is inconclusive or has been interrupted by an incident warning from the main system. It will be apparent that an incident warning generated by the detection apparatus 5 must take precedence over the test procedure and will interrupt such procedure. Tests may conveniently be carried out during the night, say during a 4-hour period starting at midnight.

The results of the test for each sounder are displayed on the VDU screen 12, are written to a floppy disc in the disk drive 14 and are printed out by the printer 13.

As described above, the sounder test stimulus, i.e.

the type of test signal applied to a sounder, is dependent upon the type of sounder, but installations will generally have a majority of one type of sounder, usually intelligent.

The test is sensitive enough to detect a reduction in sounder output due to an obstruction placed adjacent the sounder, thereby diminishing the effectiveness of the warning signals. By way of example, this might be a pair of step ladders obstructing the sounder device, or masking tape which has been applied during decoration of the premises and has not subsequently been removed.

Although audible warning devices have been described above, monitoring apparatus in accordance with the invention is equally applicable to optical warning systems. By substitution of light-generating devices (e.g. Xenon flashing strobes) and suitable optical transducers (e.g. photo-electric cells) the apparatus is capable of monitoring optical warnings and emergency lighting. For example, airport landing lights or security incident floodlighting can be easily monitored on a continuous or intermittent basis. Colour filters may be interposed between the light generators and the optical transducers in order to achieve a frequency-dependent light intensity characteristic.

Fig. 4 is a flowchart of a typical sequence of operation for an incident warning system including monitoring apparatus according to the invention. In a step 25 a START command is issued. This represents the start of system monitoring and occurs when the system is switched on. The first logical step in the flowchart is a step 26 in which it is determined whether it is time for a routine test. If it is not time for such test, a step 27 determines whether a test has been requested by an operator. If the answer is "no", the system is monitored in a step 28 to determine whether an incident has occurred. If the result is negative (step 29), the system returns to the step 26 and the interrogation is repeated.If the result is positive, i.e. an alarm is to be sounded, any test sequence which is already in progress is interrupted (step 30) a table listing the priority of sounders is consulted (step 31) and the relevant sounders for the particular incident are energised (step 32). The incident is displayed on the VDU 12 (step 33) and details are printed-out and are written to a floppy disk (step 34). The officer in charge must then acknowledge the incident before the system can be cleared. If he does not do so (step 35) the system will return to step 32 and will continue to cycle through the steps 32, 33, 34 and 35 so that the sounders continue to operate. When the officer does acknowledge the incident in step 35, the operation of the sounders is cancelled and a report is logged to the VDU 12, the disk drive 14 and the printer 13 (step 36).From the step 36 the system returns to the first logical decision at the step 26.

Returning to the step 26, if it is determined that it is time for a routine test, generation of the test tones and signals is enabled (step 37). Similarly, a positive answer in step 27 puts step 37 in operation. All of the data interfaces are addressed, in turn, to interrogate the responses of the various detection circuits (step 38). The status of each sounder is displayed on the VDU 12 (step 39) and a status report is printed out (step 40) and is written to the disk (step 41). Again the report must be acknowledged by the officer in charge (step 42). If it is not acknowledged, the system will return to steps 39 and 40 and will continue to cycle through the steps 39, 40, 41 and 42, in order to maintain the display status of sounders on the VDU until an acknowledgement occurs at step 42.When the report is acknowledged, a print of the acknowledgement is generated and written to disc (step 43), and the system returns to the first logical step at 26.

A second embodiment of an incident warning system is partly illustrated in Figure 5 although the incident warning detection apparatus has been omitted for clarity.

In this embodiment, the system comprises a number of groups of reporter units 50-1, 50-2, 50-3 etc., each group of units being associated with a particular zone in which groups of incident warning detection apparatus are located. Each reporter unit is coupled with a respective loud speaker unit 51-1, 51-2, 51-3. It will be seen by comparison of this system with the embodiment shown in Figure 1 that the speakers 51-1 etc correspond to the loudspeaker 1 while the reporter units 50-1 correspond to the routing circuit 3, transducer 7, and detection circuit 8. The reporter units 50-1, 50-2, and 50-3 of each group are connected in a loop by respective common data highways 52-1, 52-2, 52-3, each of which comprises two wires and enables the reporter units to communicate with a respective satellite unit 53-1, 53-2, 53-3 associated with that zone.The loop also contains an audio amplifier unit 54-1, 54-2, 54-3 to amplify the information passing along the data highway.

Each satellite unit 53-1, 53-2, 53-3 is capable of operating on a "stand alone" basis and contains a real time clock as well as a microprocessor which can be programmed by the connection of simple keyboard equipment (an ASCII terminal). The satellite unit can also be connected to a printer unit (not shown). The satellite units also contain respective power sources for feeding power along the corresponding data highways to the reporter units 50-1, 50-2, 50-3 connected to that highway.

In operation, each satellite unit 53-1, 53-2, 53-3 sends a "packet" of data to the reporter units 50-1, 50-2, 50-3 on its data highway to cause those reporter units to actuate the speakers 51-1, 51-2, 51-3 with a test signal. This is similar to the operation of the Figure 1 example. The transducers in the reporter units (not shown) detect the audio signals generated by the loud speakers and generate the two state signal depending upon whether or not the detected signal is correct, again in a similar manner to the embodiment shown in Figure 1.

This two state signal is combined with other data identifying the reporter unit concerned and its status, and this "packet" of data is then sent along the data highway 52-1, 52-2, 52-3 to the respective satellite unit 53-1, 53-2, 53-3 when requested by the satellite unit.

Each packet has a "Header" which contains the address of the destination unit, that unit (a reporter unit or the satellite unit) then detecting its own address in the header of the incoming packet and reading the data contained after the header. If the header does not contain the address of the unit, the unit simply passes the packet on to the next downstream unit without reading it.

As mentioned above, each satellite unit 53-1, 53-2, 53-3 can by itself provide an output on a local printer of the information from the reporter unit. However, the satellite units could be connected to a common central computer unit 55. This central computer unit 55 may control each satellite unit so that the satellite units transfer the data read from their reporter units to the central unit where the data can be stored in a conventional mass storage device 56, or the raw data can be processed and displayed either on a local printer 57 or on a visual display unit 58. The central computer unit 55 is also connected to a keyboard 59 to allow operator control.

The central computer unit 55 can address each satellite unit 53-1, 53-2, 53-3 in turn on a data highway and pass programming instructions and accept data, status and test reports.

An important feature of the satellite and central computer link is that if the data highway providing that link is lost for any reason (for example due to damage, fire, or theft) the satellite units immediately continue to operate with the last status position uploaded from the central computer unit 55, provided local printers are connected.

For high integrity situations, it is desirable to use Mineral Insulated Copper Clad Cable (for example "Pyrotenax") also known as "MICC". This cable can withstand physical abuse and high temperatures.

The audio supply cable from each reporter unit 50-1, 50-2, 50-3 to the loud speakers 51-1, 51-2, 51-3 and the data highway cables can be conveniently combined into one four core MICC cable, each loudspeaker or sounder (or Beacon) mounted on the cable which traverses a building as a loop ie. the free ends are joined back to the terminating equipment.

In some cases, there can be problems of interference between the two conductors carrying 100 volt audio distribution signals and the two conductors carrying the data highway, both within the copper cladding of the cable. This can be overcome by using a low impedance source for the data signal generation to reduce interference from the audioline to the data line; and by using a data repetition frequency which ensures that the resulting induced crosstalk in 100 volt audiolines is above the threshold of hearing.

Claims (8)

1. Monitoring apparatus for an incident warning system which includes at least one audible or visual alarm device and means to operate the device in response to detection of an incident, the apparatus comprising sensing means located to receive an audible signal or a light signal from the alarm device; and means responsive to failure to detect such signal of at least a predetermined amplitude to give warning of incorrect operation of the device.

2. Apparatus according to claim 1, wherein the sensing means is frequency-dependent and detects whether the received signal includes a signal component of at least a predetermined amplitude at a predetermined frequency.

3. Monitoring apparatus according to claim 1 or claim 2, wherein the sensing means includes means to generate a two-state digital output having one state in response to detection of said signal and having the other state in response to failure to detect said signal.

4. Monitoring apparatus according to any of the preceding claims for use with an intelligent alarm device, the sensing means being adapted to detect whether the received signal includes two components of predetermined amplitude at predetermined frequencies spaced apart in the frequency spectrum of the received signal.

5. Monitoring apparatus according to any of the preceding claims for use with an incident warning system which includes a plurality of audible or visual alarm devices and means to operate the devices in response to the detection of an incident, the monitoring apparatus comprising a corresponding plurality of reporter units, each reporter unit comprising means for operating the device and means for detecting the signals generated by the audible or visual alarm device associated with that reporter unit; and at least one satellite unit connected to a number of the reporter units, the satellite unit being adapted to receive information from the reporter units and to provide corresponding output signals related to the status of the audible or visual alarm devices.

6. Monitoring apparatus according to claim 5, further comprising a central control unit connected to each of the satellite units for receiving information from the satellite units and providing corresponding output signals.

7. Monitoring apparatus for an incident warning system substantially as hereinbefore described with reference to either of the examples shown in the accompanying drawings.

8. An incident warning system including monitoring apparatus according to any of the preceding claims.