GB2223339A - Alarm system - Google Patents

Abstract

The alarm system incorporates one or a plurality of sensors 12, 13, 14, 15 (40 Fig. 3, not shown) for detecting the occurrence of any of a plurality of alarm events, solid state digital storage means 26 (63) for storing information representing one or a plurality of alarm messages associated with respective detectable alarm events, and electronic circuit means 30, 31, 32, 33 responsive to the generation of a sensor signal and operative to generate a synthesised speech signal associated therewith from the information stored in the memory. In one embodiment, a detector (40) for detecting the presence of smoke in the atmosphere in an enclosed environment such as a room or passageway within a building, operates to produce an electrical signal when the presence of smoke is detected therein, and synthesised speech signals are generated by an integrated circuit (63) in response to the said electrical signal for activation of an acoustic transducer (66). <IMAGE>

Description

AN IMPROVED ALARM SYSTEM The present invention relates generally to alarm systems, and specifically to alarm systems having a greater range of applicability than conventional alarm systems, capable of generating a localised or remote synthesised speech signal identifying both the nature of the detected event and the location thereof.

Conventional alarm systems are usually dedicated to a specific detectable event. For example, a fire alarm system will provide an alarm output signal when smoke or high temperatures are detected, and the alarm signal itself is generally provided at or close to the protected environment. Likewise, an intruder alarm is usually provided with an alarm bell located on the outside of a building protected by sensors at the openings, and acts to energise the alarm bell when the sensors detect an intruder by any one of the many sensing phenomena which may be employed.Identification of the location of the detected event is then immediately provided by the location of the alarm bell although it is not always immediately apparent from the alarm signal exactly what is being signalled: in other words, it cannot always be immediately identified whether an alarm bell is providing a signal that an intruder is breaking in to a part of the building not immediately visible or whether smoke is being detected in a part of the building but not yet forming part of a fire which can be seen from the outside. Similarly motor vehicle alarm systems usually produce a load signal when triggered but in a crowded car park it is not immediately possible to identify which vehicle is emitting the signals. Such known alarm systems are, therefore, of limited value.

It is also possible for remote alarm signals to be generated, for example by connecting the alarm system to a land line for monitoring by dedicated monitoring stations or a local Police Station, but such a remote capability requires the use of a dedicated line since it is only by identifying the incoming line that it is possible to determine the location of the alarm signal.

Again, the nature of the alarm signal is very crude, comprising only a tone or light signal indicating that a detector has been triggered. No more sophisticated signalling is currently available.

The present invention seeks to provide an alarm system which will overcome many of the disadvantages of conventional alarm systems, which will be capable of providing detection of one of a number of different types of detectable event, such as a fire, a flood, intruder or other detectable event, and which will be able to provide an output signal which very precisely identifies both the nature and the location of the detected event. Alarm systems formed in accordance with the present invention can be used not only on buildings, but also on motor vehicles, trailers, caravans, boats or any other property which it is desired to maintain secure.

According to one aspect of the present invention, therefore, an alarm system incorporates one or a plurality of sensors for detecting the occurrence of any one of a plurality of alarm events, solid state digital storage means for storing information representing one or a plurality of alarm messages associated with respective detectable alarm events, and electronic circuit means responsive to the generation of a sensor signal and operative to generate a synthesised speech signal associated therewith from the information stored in the memory.

Because a synthesised speech signal is generated by triggering a specific sensor it is possible for each sensor to have an associated message. For example, the speech signal may be sufficiently precise to identify that an intruder is entering by a specific opening in a building, or that a fire has been detected on a particular floor or even a particular part of a given floor in a building: when applied to movable property such as motor vehicles, caravans or boats the speech signal may include an identification of the property as well as the detected event. For example the message might be "Red Vauxhall registration No. F123 ABC is being stolen". Such message may be broadcast continuously from a suitably placed loudspeaker on the vehicle.

The synthesised speech signal may itself be used in any one of a number of ways to raise the alarm. In a first embodiment of the invention the synthesised speech signal is amplified and supplied to loudspeakers located at convenient positions in the vicinity of the protected environment to act both as a deterrent for intruders and an alerting warning for the Police and/or passers-by.

Alternatively, or additionally, the synthesised speech signal may be transmitted along a telephone line and, because the information contained in the signal is so specific, it is no longer necessary to use a dedicated line, but rather a conventional telephone line may be used. Such a system may incorporate a store of telephone numbers which can be called in sequence to raise an alarm since it is only necessary for a receiver of the telephone call to lift the handset to hear in detail the nature of the detected event. A dedicated monitoring service may act, in combination with the Police, therefore, to provide supervision of a large number of buildings and/or the owners or managers of a property may also be alerted after or before the Police and/or monitoring service via such a remote link.

In another aspect the present invention provides a method of producing an alarm system for generating synthesised speech alarm signals in response to the occurrence of a detected alarm event, comprising preparing a circuit including alarm sensors, solid state digital storage means, and a speech synthesiser circuit, including the steps of entering into the digital storage means data operative related to at least one detectable alarm event capable of interacting with the speech synthesiser circuit to generate an output electrical signal representative of a speech alarm indication.

In practice, therefore, the enterprise producing the alarm systems will be provided with a list of the required alarm messages to be generated upon triggering of each of the sensors: each message may be uniquely related to an individual sensor or a number of sensors may be grouped to generate a given message; the stored memory signals are then permanently available to one or a plurality of sensors, upon triggering, to generate the required synthesised speech output.

The speech synthesiser, may, in fact, be situated at a location remote from the sensors and simply triggered by appropriate signals therefrom. In such a system the synthesiser may for example be located at a monitoring station or at a Police station, and joined by a telephone activator and land line. This system also avoids the requirement for a dedicated land line since the ordinary incoming telephone line can be fed through a plurality of potentially activated circuits to generate a synthesised speech signal recognisable by the supervising personnel when an appropriate code is received. No identification of the code is required and therefore no special training of the Police personnel. Such a message may, for example, read "intruder detected in rear entrance to 21 River Street, Any town".

The same system may also be used to generate a different signal if a different sensor of the system is triggered.

For example, if a fire sensor of the system is triggered by smoke or high temperatures the same synthesiser may provide a message "fire detected on second floor rear hallway of 21 River Street, Any town".

The remote synthesised speech signals may be supplemented by local acoustically generated signals from loudspeakers in the building and in the environment immediately surrounding the building.

In this way an alarm system is uniquely adapted to provide signals related to the location of the system and the nature of the detectable events so that ready identification of an alarm situation can be made by the emergency services.

Embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block schematic diagram illustrating in broad outline the nature of an alarm system formed as a first embodiment of the present invention, Figure 2 is a block schematic diagram of the alarm system of Figure 1; and Figure 3 is a circuit diagram of a second embodiment of the present invention.

In Figures 1 and 2 of the drawings the embodiment of the invention has been shown as an alarm system for a building, although it will be appreciated that the range of applicability extends beyond this to any sort of property or detectable event. Figure 1 illustrates a building generally indicated 11 having four sensors identified 12, 13, 14, 15 of which the first two, namely sensors 12, 13 are fire sensors at a suitable location within the building, for example at ceiling level, and the latter, namely the sensors 14, 15 are intruder alarms located on a window and a door respectively.All of the sensors 12-15 are connected by respective lines to an alarm system 16 which includes a digital data memory containing the necessary information for generating synthesised speech signals which produces an output signal to a control circuit 17 which acts to energise a telephone routing mechanism to make a telephone connection to a remote location for example a Police station or a Fire station and also to route the signals along line 18 to a loudspeaker provided on an outside wall of the building 11.

If, for example, a fire is detected by the sensor 12 located at the rear of the building the alarm system 16 generates a signal which is in digital form to the controller 17. Part of the digital signal represents the synthesised speech and a part the control signals for generating, for example, the telephone number of the local Fire brigade to cause the telephone system 19 to make a connection on the line 20 to the receiving set 21 at the Fire station. At the same time the speech signals are routed via a digital to analogue converter 22 to the loudspeaker 23.

Alternatively, if one of the sensors 14, 15 is triggered the digital data signals generated by the system 16 include information identifying the necessary connections to be made to the telephone line 24 to the Police station identified by the telephone handset 25. In this case the external loudspeaker 23 may not be energised in order to maximise the possibility that the Police, responding to the synthesised speech signals transmitted along the line 24 will be able to reach the building 11 before the intruder has escaped. In other circumstances, of course it may be important to seek to use the alarm as a deterrent, in which case the triggering of the sensors 14, 15 would also result in simultaneous broadcasting of the alarm signal on the loudspeaker 23 in order to seek to cause the intruder to depart.In this case the speech signals broadcast on the line 23 may also include a synthesised speech message indicating that the Police have been alerted, again with the intention of causing the intruder to leave the presmises as quickly as possible.

Turning now to Figure 2 the alarm system 16 illustrated in Figure 1 is shown within the broken outline 16 of Figure 2. The sensors 12,13,14,15 correspond to those in the embodiment of Figure 1, although it will be appreciated that four sensors have been shown only by way of example and any number, whether more or less than four, may be employed within the system of the present invention. The sensors are connected to a main alarm circuit 26 which receives the individual signals from each sensor, which may be in simple analogue form, and converts them into digital signals identifying the individual sensor for output on line 27.The alarm control circuit may also include means for interrogating the sensors 12-15 to ensure that they are working and/or that the lines between the sensors and the control circuit 26 are complete and uncorrupted (that is not short circuited or open circuited by tampering). Output signals on the line 27 are supplied to a synthesis controller 28 which is connected to an erasable programmable read only memory 29 within which the information concerning the individual messages to be generated by the system are stored. The synthesis controller 28 is also connected to a microprocessor 30 which acts on the data signals supplied thereto by the controller, having taken them from the EPROM 29 to generate output speech synthesis signals on an output line 31 which leads to a shift register 32 the output of which is fed, via a digital-to-analogue converter 33 to a low pulse filter 34.The output from the low pulse filter 34 is supplied to a first output line 35 leading to the telephone control circuit 17 and to an amplifier 36 leading to a loudspeaker 37 (which may be the same amplifier and loudspeaker as the amplifier 22 and loudspeaker 23 of the embodiment of Figure 1 or a different amplifier and loudspeaker combination.

When a sensor, for example the sensor 14, is triggered this may be a simple closure of normally open contacts or opening of normally closed contacts, which is detected by the alarm control circuit 26, which generates an appropriate binary signal identifying the sensor for output on the line 27. Receipt of the binary signal on the line 27 by the synthesis controller 28 causes this to draw from the EPROM 29 the relevant data associated with this signal identifying the speech to be synthesised by the microprocessor 30. The output from the microprocessor 30 comprises a string of data bits representing the synthesised speech which is fed via a shift register 32 to the digital-to-analogue converter 33 which produces an output analogue speech signal.This output analogue speech signal is fed, via the low pass filter 34 which filters out any unwanted high frequency noise, to the telephone control circuit 35 for operation as described in relation to Figure 1. The telephone control circuit 17 could, in alternative embodiments, be energised directly from the synthesis controller 28 using binary digital signals rather than the analogue signals supplied to the line 35 by the low pulse filter 34.

Turning now to Figure 3, the circuit illustrated represents a smoke detector circuit having means for generating alarm announcements in speech form comprising an ionisation chamber 40 biased between ground and a power line 41 connected, via a protection diode 42 to the junction between two batteries 43, 44 connected in series between ground and a further protection diode 45. Output signals from the ionisation chamber 40 are applied via signal lines 46 to a first integrated circuit 47, in this case suitably a Motorola MC14467-1. A decoupling capacitor 48 is connected between an appropriate pin of the integrated circuit 47 and ground.

The circuit 47 acts to detect a change in the voltage applied on the signal lines 46 from the ionisation chamber 40, which occurs when smoke particles are detected within the ionisation chamber 40, and to generate an output alarm signal on line 49 if such voltage change is detected. This output signal is applied, via a voltage doubling circuit of known type, comprising a capacitor 50, diodes 51, 52, resistors 53, 54, 55 and capacitor 56 to apply a double-voltage triggering signal on a line 57 to a trigger circuit generally indicated 58 comprising a first field-effect transistor 59 and a second field-effect transistor 60.

The line 57 is connected to the gate electrode of the first field-effect transistor 59, whilst the source and drain electrodes are connected in series between a high value resistor 61 connected to the anode of the protection diode 45 and ground. The junction between the high value resistor 61 and the drain electrode of the first field effect transistor 59 is connected to the gate electrode of the second field-effect transistor 60 whilst the source and drain are connected between the anode of the protection diode 45 and a power supply line 62 leading to a second integrated circuit 63 containing the speech synthesiser circuitry.

In quiescent conditions, therefore, when there are no smoke particles in the ionisation chamber 40, the voltage applied on lines 46 to the detector circuit 47 result in no output signal to the trigger on line 49/57 and the first field-effect transistor 59 is therefore conductive allowing a very small current drain through the high value resistor 61 in the region of 4ua. The current drain through the batteries 43, 44, therefore, is minimal, allowing a satisfactory battery life whilst maintaining the circuitry in an alert condition to detect any change in voltage on the lines 46 indicating the present of smoke particles in the ionisation chamber 40.

Upon such occurrence the voltage at the line 49 goes negative and applies, via the voltage doubler circuit, 50 to 56 a negative voltage pulse on the line 57 causing the first field-effect transistor 59 to turn off. The voltage at the junction between the drain electrode and the high value resistor 61 therefore rises turning on the second field-effect transistor 60 allowing conduction from the batteries 43, 44 to line 62 to the speech synthesiser circuit 63 which thus commences to generate synthesised speech signals in a conventional manner. the output speech signals from the synethesiser 63 are supplied to a line 64 which are applied to an amplifier 65 the output from which is applied in a conventional manner to a loudspeaker 66.Operation of the speech synthesiser circuit of course draws a heavy current from the batteries 43, 44 and it is recommended that, should the alarm enunciator be triggered, the batteries are replaced immediately after such event in order to ensure that adequate power for driving the speech synthesiser 63 is available for any future events. A considerable sound level can be generated via the loudspeaker 66 by appropriate amplification of the synthesised speech signals, sufficient easily to exceed the minimum volume levels set by the British Standards. In addition, however, the fact that the alarm signal is provided in speech form ensures that anyone being alerted by the alarm is made immediately aware of the nature of the alarm event and, furthermore, can be advised on the appropriate action to take.For example, in different regions of a building, the synthesised speech signal generated by the generator 63 associated with the specific sensor for that area, may generate speech signals directly related to the location of the fire escapes in that region, and such message may be different for different regions within the same building. This highly sophisticated alarm announcement system thus aids the rapid evacuation of a building and avoids the possibility that the significance of the alarm may be misunderstood.

Battery condition is sensed by the detector circuit 47 via the protection diode 42 and operates to draw current through a light emitting diode 67 in very short pulses, and also to apply corresponding very short pulses to a line 68 to supply a buzzer 69 which is connected in series with a field effect transistor 70 connected between the signal line 49 and the buzzer 69 in a circuit configuration giving it a relatively low response time so that it remains conductive to allow the buzzer to operate when a short pulse is passed therethrough, but which becomes non-conductive when the negative voltage signal is applied to the line 49 thereby switching off the buzzer 69 in alarm conditions so that this will not sound to obscure the speech signals generated by the speech synthesiser 63.

The circuit of Figure 3 thus comprises a self-contained smoke detector and speech signal alarm announcer which can be housed within a self-contained casing and driven by batteries 43, 44 having a sufficiently long service life as to require replacement only at infrequent periods, with the need for battery replacement being indicated by short audio signals from the buzzer 69 and visible signals from the light emitting diode 67.

Claims (17)

1. An alarm system for detecting the presence of smoke in the atmosphere in an enclosed environment such as a room or passageway within a building, comprising an ionisation chamber smoke detector operable to produce an electrical signal when the presence of smoke is detected therein, and means for generating a synthesised speech signal in response to the said electrical signal for activation of an acoustic transducer.

2. An alarm system for detecting the presence of smoke in the atmosphere in an enclosed environment such as a room or passageway within a building, comprising an ionisation chamber operable to produce a voltage signal when the presence of smoke is detected therein, a detector circuit for producing an output triggering signal in response to the said voltage signal and trigger means responsive to the occurrence of the said trigger signal to initiate the operation of a speech synthesiser circuit for generating speech alarm signals identifying the alarm for supply to an acoustic transducer.

3. An alarm system as claimed in Claim 2, in which the said ionisation chamber, the said detector circuit and the said speech synthesiser circuit are all powered from a battery and housed in a common casing.

4. An alarm system as claimed in Claim 3, in which there is further included a battery condition sensor and means for generating an audible warning to indicate a battery low condition.

5. An alarm system as claimed in Claim 4, in which there is further provided a visible warning to indicate a battery low condition.

6. An alarm system as claimed in Claim 4 or Claim 5, in which there are further provided means for disabling the audible warning means on the occurrence of an alarm condition whereby to avoid obscuring the snthesised speech signal from the acoustic transducer.

7. An alarm system as claimed in any preceding Claim, in which the trigger means for triggering the speech synthesiser circuit comprises a transistor switch circuit operable to apply the battery voltage to the speech synthesiser upon occurrence of the said triggering signal.

8. An alarm system as claimed in Claim 7, in which the said transistor switch circuit includes a first field-effect transistor connected to receive the said triggering circuit at its gate and having its source and drain in series with a high value resistor between the supply voltage and ground whereby to maintain the said first field-effect transistor conductive with a minimum current leakage therethrough.

9. An alarm system as claimed in Claim 8, in which the junction between the said high value resistor and the drain of the said first field-effect transistor is connected to the gate of a second field-effect transistor biased such that the said second field-effect transistor is turned on when the said first field-effect transistor is turned off, whereby to apply the battery voltage to the power input terminal of the speech synthesiser circuit.

10. An alarm system incorporating one or a plurality of sensors for detecting the occurrence of any one of a plurality of alarm events, solid state digital storage means for storing information representing one or a plurality of alarm messages associated with respective detectable alarm events, and electronic circuit means responsive to the generation of a sensor signal and operative to generate a synthesised speech signal associated therewith from the information stored in the memory.

11. An alarm system as claimed in Claim 10, in which there are further provided means for amplifying the synthesised speech signal and supplying it to one or more loudspeakers located in the vicinity and/or at a location remote therefrom.

12. An alarm system as claimed in any preceding Claim, in which there are provided means for transmitting the synthesised speech signals along a telephone line.

13. An alarm system substantially as hereinbefore described with reference to, and as shown in Figures 1, 2 or 3 of the accompanying drawings.

14. A method of producing alarm systems for generating synthesised speech alarm signals in response to the occurrence of a detected alarm event, comprising preparing a circuit including alarm sensors, solid state digital storage means, and a speech synthesiser circuit, including the steps of entering into the digital storage means data operatively related to at least one detectable alarm event capable of interacting with the speech synthesiser circuit to generate an output electrical signal representative of a speech alarm indication.

15. A method as claimed in Claim 14, in which each message is uniquely associated with a given sensor.

16. A method as claimed in Claim 14, in which each message is related to a plurality of sensors grouped so as to give rise to the generation of a given message.

17. A method of producing alarm systems substantially as hereinbefore described.