GB2513733A - Emergency system - Google Patents

Abstract

A wireless emergency system comprising a plurality of units, each unit comprising a transceiver adapted to transmit and receive data to/from other units in the system, each unit comprising a tester comprising a transmitter adapted to transmit a silent message to other units in the system, and an indicator adapted to indicate to a user that a unit has 10 received the silent message and that the strength of the signal received is above a predetermined level.

Description

EMERGENCY SYSTEM

This invention relates to an emergency system, and particularly, but not exclusively to a wireless fire alarm system. The system is adapted for use in any suitable environment, but is particularly suitable for use in the construction industry.

It is known that construction sites can be potentially dangerous and therefore it is important that all necessary safety standards are met. It can be particularly important to have a reliable emergency system that will, for example warn people on the construction site or nearby, of emergencies such as fire, through the detection of fire, heat and/or smoke. It is also important that any emergency system can provide a means for manually raising an alarm by manually activating call points forming part of the system.

Also such systems should be easily adapted to, for example, the changing size of a is building under construction. This means that it is important that emergency systems for use in the construction industry have the facility to be extended or to be reduced in size as necessary to meet the changing requirements of the construction site.

A known emergency system comprises a plurality of devices that are adapted to communicate with one another wirelessly.

The devices are able to communicate unidirectionally on a strict timeslot basis depending on the number of the unit in question. In such a known system, an activated unit will send out a radio message after it has been triggered by a call point press or detection head activation. The radio message indicates the start of the transmission timing, with each device relaying the radio message sequentially in turn. There is no acknowledge mechanism for this communication method. Instead, each message is sent three times consecutively and it is assumed that at least one of the three messages has been correctly received. In addition, a predetermined length of time after the original transmission, the radio communication is repeated again in the same sequence.

Typically, there will be a restriction on the number of units forming such a system due to the particular communication protocol being used and the fact that that the protocol will depend upon the unit numbers in the system.

According to a first aspect of the present invention there is provided a wireless emergency system comprising a plurality of units, each unit comprising a transceiver adapted to transmit and receive data to/from other units in the system, each unit comprising a tester comprising a transmitter adapted to transmit a message to other units in the system, and an indicator adapted to indicate to a user that a unit has received the message and that the strength of the signal received is above a predetermined level.

The purpose of the tester is to exercise the radio communication part of the units and provide confirmation that each unit is able to communicate successfully with other units on the same site.

The message sent by the tester may be sent without any audible signal also being sent.

In other words the signal may be sent without a siren or other audible alarm also being sent. For this reason the test carried out may be described as a silent test, and may be regarded as a way of testing that the system is in a state ready to react to a situation requiring an alarm to be raised, It is to be understood however that in some embodiments of the invention, the tester may transmit a signal having an audible component to the signal.

The silent tester may be initiated from any unit in the system.

The silent tester may comprise a silent test button. The silent test button may be pressed by a user in order to activate the silent tester.

Activation of the silent tester causes the unit associated with the silent tester to send out a silent message activation, which activation causes the indicator on each other unit to indicate that the unit has received the silent message.

The indicator may provide any convenient type of indication that a particular unit has received the silent message. In some embodiments, the indicator comprises a visual indicator such as an LED indicator and/or display. This allows for convenient inspection of the system to take place in order to check that each and every unit has received the silent message.

In some embodiments of the invention, each unit comprises a delayer for delaying transmission of data by a randomised delay time, and a clear channel assessment for checking that no other unit within range of the unit in question is transmitting at that time.

The network comprises a (logical) network layer, a physical (PHY) layer and an application layer.

The delayer in each of the units reduces the probability that more than one unit will transmit at the same time.

Each unit also comprises a clear channel assessment. This component will check that no other units within range of the unit in question is transmitting or receiving at that time.

This reduces the possibility that there will be interference with other units in the same, or other systems.

A system according to the first aspect of the invention allows each unit to communicate with other units in the system using a repeated broadcast radio message. This ensures that the radio message is propagated across the network with each unit acting as a relay in a mesh-like structure.

In embodiments of the invention, the system adopts a decentralised mesh topology. In such a system there is no system map and the units in the system do not know what other units exist in the system.

As long as every unit in the system is connected to the mesh-like structure by at least one sufficiently strong link, the system will function correctly.

In some embodiments each unit will be connected to more than one other unit. Each unit can thus be regarded as having a plurality of links to other units within the system. This adds to the robustness of the system through path diversity.

Any given unit will be able to communicate with other units within its range. A unit that receives data from another unit may then in turn transmit the data to yet another unit within range of that unit. Whenever a unit receives a transmission it may then in turn transmit the data received to another unit within range of the unit in question. Each stage in this mesh-like structure can be regarded as a "hop".

The system could, in theory, have an indefinite number of units with many relay hops being required in order to ensure that all units are in communication with all other units.

However, in order to ensure timely communication and satisfy latency and power consumption requirements, in some embodiments of the invention a limit of communication hops has been placed on the system. In many embodiments the limit to the number of hops is three. Beyond three hops the system will still work but the time to propagate messages across the network may be long and cannot be guaranteed.

In any given system, data may be transmitted repeatedly with the interval between repeated transmissions being a random interval of time. When a unit receives a transmitted message it may relay the message a plurality of times also with a random interval of time between repeated transmissions.

In one embodiment of the invention, when a unit in the system wishes to communicate an event, the data may be transmitted five times at random intervals of time. When a unit hears the message it relays the message three times also at random intervals of time. In other embodiments, the data may be transmitted and relayed any convenient number of times.

For every transmission, short random delays are introduced by the delayer of typically a few milliseconds. In this way the probability of a relay clash is reduced.

A unit will therefore typically hear the same message several times.

Each distinct event is identified by a combination of the originating unit identifier and a message sequence number.

The network layer may maintain a history buffer detailing which distinct event(s) it has heard in a given period of time, known as the history buffer period, and does not pass repeats up to higher level application logic. The history buffer is defined as being between some PHY active and 30 seconds after there has been no PHY activity. Every time a relayed packet is received by the network layer it checks to see whether it has already relayed the packet and passed it up to higher level application logic. If it has, it updates its received signal strength indication (RSSI) entry for this message and does nothing else, If it has not, it passes the message up to higher level application logic, stores a new entry in the history buffer and relays the packet. 30 seconds after there has been no PHY activity, the history buffer is cleared.

The system may operate on any suitable frequency but in many embodiments the system will operate within the radio frequencies. However, it is to be understood that the system may operate within different bandwidths and may for example operate in the visible range of frequencies.

In some embodiments, each transceiver will operate in a frequency band from 868.0 MHz to 868.6 MHz.

In some embodiments, each transceiver may comprise a CC1125 Category 1 integrated half duplex radio transceiver operating at a power of 25 mW and at a frequency of 868.3 MHz. In such an embodiment each unit may have a duty cycle of less than 1%.

It is to be understood however that the transceivers could operate on different frequencies within or outside of the radio bandwidth, and could also operate at different powers.

The data may be sent in any convenient format but in many embodiments will be sent in packets. Each packet may contain an address unique to the site at which the system is installed. It may also contain a unit number to identify a particular unit, a message type to identify the type of message, a command and a 16 bit check sum or cyclic redundancy code to ensure that the received packets have not been corrupted.

A suitable data packet format is set out below.

Field Description

Site code Unique 32 bit number used to indicate which site a unit is installed on. Once paired units will only activate or respond to other units on the same site code.

Latency An indication of how long the packet has taken to cross the network, this depends upon the number of retransmissions it has had and also the CCA delay time.

Length Allows for variable length payloads.

Field Description

Source Message Combined with the source address the message number ensures Number uniqueness. This is used to keep track of relayed data packets.

Source Address A 32 bit number identifying the originator of a radio message Source Unit A human readable unit number as a label for easy identification and Number grouping CRC Cyclic redundancy code The data packets may however have some other configuration.

When operating at radio frequencies, it is preferable for over the air data to be random.

This results in the smoothest power distribution over the occupied bandwidth. To assist with this, the PHY layer implements a simple data whitening algorithm. This works on the assumption that fields of consecutive l's and fields of consecutive D's are statistically more likely in the data packets used in systems according to the present invention than

in fields of alternating l's and 0's.

Units in the systems according to the invention will look for a sync word to detect the start of a valid data packet. This can be an effective mechanism only if the sync word does not occur anywhere else in the data system.

To ensure that this is the case, a token removal algorithm is implemented.

Each data packet includes a synchronisation word, known as a token, which is constant for all data packets and allows the start of each frame to be identified, this word, or token, must therefore not appear anywhere else in the data packet. To avoid this token appearing within the data each instance of AB is replaced by -A-B-AB, where A is the first byte of the token and B is the second byte of the token and -A is the bitwise inverse of A. Wherever the token has been removed it needs to be replaced after the data packet has been received, this is performed by the following single algorithm, replace -A--BX1X2 with -X1X2.

For the one step replacement algorithm to work at the receiving end any instances of the inverse of the token need also to be replaced as they are a marker to indicate which bytes have been replaced. For instances in the data where the inverse of the token -A--B occur these are replaced with -A-BA-B which can be returned to the original -A-B using the same algorithm above, i.e. Replace -A--BX1X2 with -X1X2.

This can be further explained by an example where the sync word or token is chosen to be 0x9305 (A represents 0x93 and B represents OxOB).

(In binary 0x930B = 1001 0011 0000 1011. The inverse of this (where 1 becomes 0 and vice versa) is 0110 11001111 01000x6CF4) Any instance of AS (OxG3OB) in the packet data is replaced, according to the algorithm -A-B-AB with Ox6CF4BCOB.

Any instance of -A-B (Ox6CF4) in the packet data is replaced, according to the second algorithm -A-BA-B, with 0x6CF493F4.

These bytes will then be replaced during the receive process using the single algorithm, replace -A--BX1X2 with -X1X2.

e.g. for Ox6CF46COB, the receiver finds the inverse token Ox6CF4 and replaces it with 0X930B.

e.g. for 0x6CF493F4, the receiver finds the inverse token Ox6CF4 and replaces it with OX6CF4.

A 16 bit CCITT CRC (X16+X12÷X5+1) is used to detect packet corruption. In the receive direction the CRC check is performed by the transceiver. In the transmit direction, efficient CRC generation is performed by the PHY layer.

In some embodiments of the invention the transceiver is powered for some of the time only. In such embodiments, the transceiver may comprise a Wake On Radio component. This enables the power consumption of the transceiver to be optimised whilst permitting low latency communication. This in turn increases the battery life of the unit.

In embodiments of the invention, the units forming a system according to embodiments of the present invention may be battery powered. Each unit must be ready to react immediately to any given event. This means that a low power sleep mode in which a unit is nevertheless still capable of receiving data is advantageous.

This can be difficult to achieve since the unit requires significant power in order to listen for incoming data. In a particular embodiment in which each unit comprises a OC1 125, transceiver a method for automatically polling for data activity may be used.

This mode of operation may not always be sufficient however in order to guarantee reception of data, because in order to guarantee receipt of data, a data packet preamble longer than the maximum allowed by the CC1125 must be achieved.

The inventors have nevertheless realised that this may be achieved using CC1 125 transceivers, through appropriate configuration of data packets In particular, the inventors have realised that if the sync word, length field, address field, and some of the data payload are programmed to be the preamble data word (repeated), and then these same fields are instead manually (not automatically by the transceiver) inserted after this extra preamble data, a preamble longer than the maximum supported by the transceiver (according to its datasheet) can be realized and thus a low power sleep mode may be achieved In order for this to function correctly, digital data processing normally performed in the transceiver must be performed manually in the PHY layer.

In units according to embodiments of the invention, the PHY layer has different transmit and receive configurations.

In the transmit direction, the PHY provides a fully processed packet with a non-standard extra long preamble which the unit transmits transparently. In the receive direction, the advanced features of the transceiver in the unit are leveraged to enable optimum sleep level and duration.

Because it is necessary in some embodiments to configure the transceiver of the unit in between receiving and transmitting data, the CCA (Clear Channel Assessment) is performed instead by firmware provided in the PHY layer.

In such embodiments therefore the PHY layer listens to ascertain whether the radio channel is clear. If it is it proceeds with transmission. If it is not it waits for a random back off of typically a few milliseconds and then tries again.

This listen and back off cycle is repeated for up to 10 seconds (although other time periods could be used) at which point the PHY will transmit regardless of the channel traffic.

In a particular embodiment of the invention each transceiver will draw an average current of approximately 6OpA without an additional receive amplifier, and approximately lOOuA with an additional amplifier to provide increased range.

Each unit may comprise a microprocessor for controlling operation of the unit.

The delayer and clear channel assessment may form part of the microprocessor.

The microprocessor may determine whether any received data packets have a site address which matches the site address of the system. If a received data packet has an address matching the full site address, the data within the data packet will be processed and actions will be performed by the microprocessor.

The microprocessor may remain in a low power sleep state until a data packet is received which matches part of the site code and has passed a cyclic redundancy code check indicating that there is a high probability that the packet has been received error free.

The unit may comprise a monitor for monitoring the signal strength of transmitted and received data. This is to ensure that at least one data packet from a unit is above a required attenuation reserve threshold. The monitor may form part of the microprocessor.

In particular, if a unit receives radio messages from peer units within the history buffer period, but none of the signals within that period is above a reliable signal strength, a low radio warning will be raised.

In parallel, if a period of PHY activity is started by a transmit operation originating at a local unit, the network will expect to have heard at least one relay of this message from a neighbouring unit by the end of the history buffer period. If no relay is heard, a separate radio absent warning will be raised.

Each unit may comprise an attenuation reserve threshold.

The attenuation reserve threshold determines whether a signal has sufficient signal strength. The purpose of the attenuation reserve threshold is to allow for variations in the received signal strength due to external environmental changes which may include atmospheric conditions, unit positioning, movement of people, furniture, equipment etc. The attenuation reserve artificially raises the minimum required received signal strength to provide a margin of safety to help ensure radio messages are robustly received and not operating near to the point where a radio signal might not be correctly received. The system uses the attenuation reserve threshold during silent tests such that units which correctly receive a signal which is above the threshold will successfully enter the silent is test mode, units which correctly receive a signal which is below the threshold will fail the silent test and will indicate a low signal" warning instead.

For fire alarms however, the attenuation reserve threshold will be disregarded and all units which correctly receive a radio message will enter the fire alarm state.

The monitor also monitors the PHY layer, so if a PHY operation takes too long, the PHY is reset. Whenever the PHY is requested by the network layer to perform an action (e.g. to send a packet), the network layer starts a timer. If the timer expires before the PHY calls the network layer back to signal successful completion, the network layer assumes that there is something wrong with the PHY layer (or the transceiver it abstracts from) and performs a PHY reset sequence to return to functional state.

Each unit may comprise a fault warning unit for transmitting a fault signal in the event that the signal strength of the data packets falls below the attenuation reserve threshold.

Under such circumstances communications will continue but a signal from the unit indicating the fault will be transmitted and displayed. The fault warning may form part of the microprocessor of each unit.

A unit which initiates (not relays) a radio message listens for the radio message being relayed onwards by other units as confirmation of correct receipt of the message. If this radio echo' is not received then the unit indicates a fault.

The units in the system may comprise any suitable units, and when the system is a firepoint system, at least one of the units comprises a firepoint device. In such a system at least one of the other units comprises a detector unit adapted to detect smoke/heat, although it is not necessary to have such units.

In such a system, alarm messages are acted upon by the one or more firepoint units.

The system may also comprise a base unit comprising an identifier adapted to identify which of the one or more units of the system has been activated. The base unit may then emit an alarm message in response to identifying one or more units having been activated. The identifier may form part of the microprocessor.

It is not necessary for a system according to the first aspect of the present invention to have a base unit, but some embodiments will have such a unit which preferably may be positioned inside a building or an enclosure. There is however no requirement for the base station unit to be positioned indoors it is typical for it to be in a site cabin but could equally be located outside.

In all systems whether with or without a base unit it is possible to identify which units have been activated by visual inspection of each unit.

In some embodiments of the invention, each detection unit will have a visual indicator of an alarm state In some embodiments of the invention this visual indicator comprises an LED display.

The period of time for which a detection unit may emit an alarm signal may be any convenient time, and in some systems is 30 minutes, unless the fire alarm is cancelled before the lapse of that time period.

In some embodiments of the invention firepoints which have initiated an alarm by being activated may indicate the alarm state by means of a mechanical flag which is visible to an observer.

In some embodiments of the invention, if any of the units within the system is manually activated, an activation alarm may be emitted by that unit for as long the unit remains manually pressed.

The signal that is emitted may comprise an audible signal.

The audible signal may comprise a siren chirp.

S In some embodiments of the invention, a unit may be manually activated by a user pressing a button to activate the unit. In such embodiments, the activation alarm may be emitted for as long as the button remains pressed.

In some embodiments the base station unit comprises an internal GSM modem and antenna.

The base station may comprise a display unit. The display unit is adapted to indicate to a user which of the units in the system has been activated. The base station may also be adapted to display information relating to units having low battery power, units that have been tampered with, or those having a poor radio signal.

The units forming a system according to embodiments of the invention are sealed at the manufacturer with a battery pack connected within the unit to avoid the need to open and possibly damage the unit during installation.

In order to conserve battery power and to permit safe transportation of each unit by van, boat, aeroplane etc, each unit may be placed into a low power mode, known as a transit mode. In this mode the transceiver is disabled to prevent transmission or reception of any messages and all electronic circuitry is placed into the lowest power state. Pressing a call point or activating a detector head in transit mode for example, will have no consequence.

In an embodiment of the invention, a unit may be put into transit mode by holding a pair button and then pressing a test button three times in quick succession. The unit indicates it is entering transit mode by, for example illuminating a plurality LEDs.

Additionally if the unit has already joined a site network it will send a message to inform the base station (if fitted) that a unit has been put in transit mode and is therefore no longer part of the installed system.

A unit is brought out of transit mode by following the same button press sequence of holding pair button and triple pressing test button. Units being brought out of transit mode have their site code details returned to default and are ready to be installed by pairing with another unit Unit numbering is unaffected by this process.

In other embodiments, different processes may be followed.

The units may comprise a back tamper component. The back tamper component is adapted to indicate when a unit has been removed from either a wall or a ceiling, for example on which it has been mounted. Typically, a firepoint unit will be mounted on a wall whereas a smoke/heat detector may be mounted on a ceiling.

The back tamper component is adapted to be resettable by reaffixing the unit to a wall/ceiling as appropriate.

Once the unit has been reaffixed it will confirm that it can communicate with at least one other component in the system The back tamper unit is adapted to perform a radio check when the unit has been reinstalled.

Each unit may comprise a first housing component adapted to receive and contain electronics and/or firmware associated with the unit, and a second housing component comprising a first connector for connecting to the electronics and/or firmware contained in the first unit.

The electronics may be in the form of an electronics board.

The first connector may be used to form connections with different electronic components in the first housing depending on the behaviour of the detection unit that is required.

The first housing component may comprise a second connector operatively connected to the electronics and/or firmware. When the electronics comprises an electronics board, the second connector may be mounted on the electronics board.

The first connector is adapted to engage with the second connector.

The first connector may be designed so that only certain connections are made when the first connector and the second connector engage with one another.

For example, in a system comprising firepoint units, heat detectors and smoke detectors, S each of these types of detectors may be formed from a first housing comprising substantially identical electronics and/or firmware. However, when the first connector engages with the second connector different combinations of electronics components are connected to form part of the particular unit. The particular electronic components/firmware which are included in the overall circuitry will determine how the unit will behave and therefore whether it is a firepoint unit, a heat detector or a smoke detector, for example.

In other words, each unit within the system comprises a substantially identical first housing containing substantially identical electronics and/or firmware. The behaviour of the unit is determined when the connection is made between the first housing component and the second housing component.

The second housing component may comprise a fascia adapted to engage with the first housing component to form a closed housing.

The fascia may have different features depending on the type of unit that is to be formed.

For example, all firepoint units may look the same whereas all heat detectors may look different to the firepoint units, and may all be similar to one another.

The first connector may comprise a membrane connector comprising a flat ribbon cable, although any other type of connector may also be suitable.

If a flat ribbon cable is used, the cable may comprise connections printed onto a flexible substrate.

The cable may comprise a terminal connector which is adapted to engage with the second connector. The second connector may comprise a connector mount operatively connected to the electronics/firmware.

In one embodiment of the invention, the first connector comprises four connections, although in other embodiments a different number of connections may be present.

In a connector having tour connections, up to 16 different combinations of connection are possible. In other wards, by determining which one or more of the connections are connected in use with corresponding connections in the first unit, 16 different types of unit behaviours may be provided.

A logical zero is produced by not connecting that particular connection, and a logical one is produced by forming a connection between the connector and a connector to a particular electronics component.

All connections may be kept close to the terminal end of the fascia in order to reduce the possibility of electro-magnetic incompatibility problems and to obviate the need for electro-static discharge protection.

Looping the connections to the far end of the fascia brings the lines dose to the unit enclosure which could increase the susceptibility of electrical noise and electro-static discharge.

All of the units forming the system may have substantially the same first housing holding the same electronics for all units in the system. The connector of the fascia will determine whether the unit is, for example, a firepoint, a smoke/heat detector, or a base unit.

This is an important feature of the invention as claimed since it means that the first component is common to all devices forming the system.

According to a second aspect of the invention there is provided a unit for forming part of an emergency system, the unit comprising a transceiver adapted to transmit and receive data to/from other units in the system, each unit comprising a tester comprising a transmitter adapted to transmit a message to other units in the system, and an indicator adapted to indicate to a user that a unit has received the message and that the strength of the signal received is above a predetermined level.

Other features of the unit described herein above with reference to a system according to the tirst aspect of the present invention may also be present in a unit according to the second aspect of the present invention.

According to a third aspect of the present invention there is provided a wireless emergency system comprising a plurality of units, each unit comprising a housing having a first housing component adapted to receive and contain electronics and/or firmware, and a second housing component engageable with the first housing component to form a closed housing, the second housing component comprising a first connector for connecting to the electronics and/or firmware.

The units forming a system according to the a third aspect of the present invention may have one or more other features of the unit described hereinabove with reference to a system according to the first aspect of the present invention.

In such a system, all of the units forming the system may comprise identical first housing component, and a may comprise identical electronics and/or firmware.

is According to a fourth aspect of the present invention there is provided a method of testing a wireless emergency system comprising a plurality of units, each unit comprising a transceiver adapted to transmit and receive data to/from other units in the system, the method comprising the steps of: causing one of the units to transmit a message to other units in the system; checking that all other units in the system have received the message and checking that the strength of each signal received is above a predetermined level.

The method may comprise the further step of setting an attenuation reserve threshold for each unit; and checking that the signal received by each unit is above the attenuation reserve threshold.

The invention will now be further described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic representation of an emergency system according to an embodiment of the first aspect of the present invention; Figure 2 is a flow diagram showing how data is transmitted around the system of Figure 1; Figure 3 is a schematic representation of a device in the form of a firepoint forming part of the system in Figure 1; Figure 4 is a block diagram of the firepoint device shown in Figure 3; Figure 5 is a schematic representation of a device in the form of a smoke/heat detector forming part of the system of Figure 1; Figure 6 is a block diagram of the detector shown in Figure 5; and Figure 7 is a schematic representation of a device in the form a detector forming part of the system of Figure 1; Figure 8 is a block diagram of the base station shown in Figure 7; Figure 9 is a block diagram illustrating the test feature of an embodiment of the invention; Figure 10 is a flow chart showing how a test procedure would be carried out in an embodiment of the invention; Figure 11 is a schematic representation showing the inside of a housing suitable for forming any of the devices illustrated and described hereinabove; Figure 12 is a schematic representation showing the first connector forming part of the fascia which is adapted to engage with a second connector on a main printed circuit board contained within the housing of the devices; and Figure 13 is a detailed representation of the first connector shown in Figure 10; Figures 14 to 17 are schematic representations showing different types of connectors that could be used in a system according to embodiments of the invention.

Referring initially to Figure 1, an emergency system according to an embodiment of the first aspect of the invention is designated generally by the reference numeral 2.

The system 2 comprises a plurality of units 4 which are positioned at various locations on a construction site. However it is to be understood that the units could be installed in any desirable location.

In the illustrated system 2 there are four units identified by the reference numerals 6, 8, and 12.

Each of the units comprises a delayer 12 (shown in Figure 2) for setting a randomised delay time between either activation of the unit or receipt of data by the unit from another unit.

The system 2 adopts a decentralised mesh topology. As such there is no system map and none of the units 4 know which other units 4 exist in the system.

As long as every unit in the system is connected by at least one sufficiently strong link, the system will function correctly.

It can be seen that some units, in this case unit 8 are connected to more than one other unit. Unit 8 is connected to two other units 6, 10 by a sufficiently strong link, and to a third unit, 12, by a weaker link illustrated by a broken line.

Due to the plurality of links the system has a degree of robustness.

Turning now to Figure 2, a flow chart shows how data is transmitted around the system 2. If one on the units 4 wishes to transmit data regarding an event, the delayer 12 forming part of the unit will generate a randomised delay which in this example is between 7 and 70 milliseconds in one millisecond steps.

A clear channel assessment 14 will then check to see that no other units within range are transmitting.

is If the channel is clear, the data will be transmitted.

In the illustrated embodiment, data will be transmitted five times at random intervals.

This is achieved by means of the incremental transmit counts 16, 18. Once the data has been transmitted five times, the transmit count will be cleared at the transmission procedure will have finished.

If the clear channel assessment shows that the channel is not clear, the delayer 12 will cause a randomised delay of between 7 and 70 milliseconds in one millisecond steps, and will repeat this process until the clear channel assessment shows that the channel is clear.

Turning now to Figures 3 and 4 a firepoint unit, is illustrated schematically.

The firepoint unit shown in Figure 3 and is illustrated schematically by the reference numeral 30, the device comprises an antenna 32 fixable inside the housing 20. The housing is held together by screws 34. Inside the housing are electronics and firmware shown in more detail in Figure 4. The firepoint device 30 comprises a pair button 36, a silent test button 38, an alarm LED 40, a fault warning LED 42, a unit activate LED 44, a call point 46 and sounder 48. These components will be described in more detail hereinbelow. The housing 20 also comprises wall mounting points 50 which enable the housing 20 to be mounted on a wall.

The housing comprises a first housing component 90 (shown in Figure 9) in which the electronic/firmware is housed, and a second housing component 92 in the form of a fascia which is attachable to the first housing unit. In this example, the second housing component (the fascia) is attached to the first housing component by the screws 34.

Turning now specifically to Figure 4, the electronics contained within the first housing component 90 are shown in more detail. The unit comprises a microprocessor 505 controlling operation of the unit 30. The microprocessor contains within it the delayer 12 and clear channel assessment 14, amongst other components. Other pads of the electronics will be described herein below with reference also to the electronics forming other units within the system.

Turning now to Figures 5 and 6 a smoke/heat detector is designated generally by the reference numeral 300. Parts of the detector correspond to parts of the firepoint device is 30 have been given corresponding reference numerals for ease of understanding. As well as the common components identified in Figure 5, the detector 300 further comprises a smoke/heat detector unit 310.

A base station 400 is illustrated schematically in Figures 7 and 8. Parts of the base station 400 corresponding to parts of the firepoint 30 and the smoke/heat detector 300 have been given corresponding reference numerals for ease of understanding.

In addition to the components that are common to one or both of the other devices 30, 300 the base station further comprises a LCD display 410, and navigation buttons 420.

Turning now particularly to Figures 4, 6 and 8, it can be seen that each of the three types of devices 30, 300 and 400 have the same electronics which are designated generally by the reference numeral 500, and which are held within housing 20.

Set out below are details of the components shown particularly in Figures 4, 6 and 8.

Component Description ______________________________ 24V Siren Loud siren, powered from 24 volts, used to warn building ____________________ occupiers of a fire to allow evacuation Antenna Flexible, whip antenna, optimised for 868MHz Back Tamper Sprung switch with normally open contacts and associate cable and connector on the rear of the unit. Used to indicate removal ____________________ from waD!ceng Battery Pack Nominal 23Ah 6V Alkaline battery pack with secure, polarised _____________________ Co fl nector Detector Base Electro mechanical fitting used to secure one of a number of different detection heads (smoke, heat 52 deg C, heat 90 deg C, ____________________ dual detection) Detector Interface Provides signal to microprocessor to indicate unit has triggered.

Circuitry Allows latched alarm to be reset by cycling power to the __________________ detection head EEPROM Non-volatile memory used for storing event logs such as alarm, ____________________ silent test, low battery etc. Internal Tamper Tamper switch located on main PCB which identifies when the ____________________ enclosure has been opened and raises a fault Latching Call Point A call point which, when pressed, mechanically latches into _______________ place and can only be reset using a key Microprocessor Control and decision making element containing firmware code PC for development Connection to a PC via USB for debugging and testing of system test and debugging ____________________________ ____ _____________ Radio transceiver Plug on 868MHZ radio transceiver daughterboard with connector daughterboard for antenna Reverse Polarity Circuitry which prevents damage to units in case of incorrectly Protection connected or wired battery pack Component _______ Description ___________________________ ______ RTCC and Unique ID Battery backed up Real Time Clock together with a Unique ID number. Unique ID used for Site Code" when starting network ____________________ to remove requirement for manual configuration.

Smoke I Heat Smoke or heat detection head which fits into detector base Detector pviding mechanical and electrical connections Switched Mode PSU Very efficient power supply architecture to provide 12/24V output for detector units and siren. Power supply output voltage can be __________ ____ selected from the microprocessor.

Tablet PC for Optional unit used to provide a Qwerty keyboard for easier entry Optional of telephone numbers and site codes. Also used to reset PIN Configuration codes and internal tampers. ____________________________ Tamper Reset Key Analogue key" used to reset internal tamper. 2 different keys will be produced, one for "Sealed by manufacturer" and the other _____________ for Sealed on site" _____ Temperature Sensor Integrated circuit giving a digital readout of temperature allowing ___________________ remaining battery capacity to be temperature compensated UART-USB External USB integrated circuit running all USB communication from a serial interface on the microprocessor, can be used when ____________________ unit operational Unit Fascia (LED's, A membrane fascia incorporating three LEDs (Red, Yellow and Buttons and Unit Green) and two push buttons (Silent Test and Pair) with a single Type) flexible cable containing electrical connections which indicate which type of unit to be. Each unit (Firepoint, Detector and ____________________ Basestation) has a different fascia. ______________________ All three types of device also have the same microprocessor 505, battery pack 510, a back tamper 520, a radio transceiver daughterboard 530 as well as antenna 32.

The battery pack 510 comprises a 12 alkaline C-cell battery pack. Due to the intermittent powering required because the sleep modes of the units, each unit will have a battery life of approximately 3 years and will have consistent performance over the entire battery voltage range.

This will be achieved by utilising a number of techniques as set out below: 1) Power Supplies -The units use switched mode power supplies instead of linear regulators to improve the efficiency of power conversion from the nominal 6 volt battery pack to provide 3.3 and 24 volt power supply outputs which are constant over the full battery range. The 24 voltage power supply output is reduced to 16V for detection units and is controlled by firmware.

2) Sleep Modes -Wherever possible the microprocessor and other integrated circuits are kept in the lowest power modes possible utilising built-in sleep and hibernation modes as appropriate.

3) Low Power Design -The electronics have been designed to ensure that the normal, quiescent state, of signals are the lowest power state with any alarm or error states drawing higher power.

Within the main board electronics that are common to all units within the system there is an internal tamper switch 540, and a detection head tamper (not shown). The internal tamper switch 540 together with the detection head tamper and the back tamper 520 which is also common to all units helps to ensure that if any units are tampered with, an alarm is sounded.

The internal tamper will be activated when the unit enclosure is opened. This tamper is indicated by a flashing LED on the unit facia and by a radio message to a base station (if present in the system configuration). The internal tamper can be reset only by an authorised user, and a log of the tamper reset is kept indicating date, time and reset key for warranty and auditing purposes.

The tamper reset key is electronic and consists of a pushbutton, potential divider (formed by a resistor network), printed circuit board and a connector. To reset the internal tamper the key" is mated with a connector on the printed circuit board then the pushbutton pressed. The main unit detects the voltage from the potential divider, if this voltage is correct then the unit can be closed and the tamper cleared in the next 30 seconds. Two different potential divider outputs have been catered for to allow for sealing by manufacturer or sealing by an end customer to allow for warranty claims to be correctly processeft The back tamper 520 detects when a unit has been removed from either a wall (for firepoints and base stations) or a ceiling (a smoke/heat detectors). This tamper is indicated by a flashing LED on the unit fascia and by a radio message to the base station (if present in the system configuration).

The back tamper can be reset by reaffixing the unit to a wall/ceiling as appropriate.

When reaffixed the unit will confirm that it can communicate with at least one other component in the system. If successful the unit will then enter its normal mode of operation. If unsuccessful the unit will indicate that it has a problem with communication by flashing its fault LED in a defined pattern.

The detection head tamper enables smoke and heat detector units to detect when a detector head has been removed from its mounting. This will be indicated by a flashing LED on the unit fascia and by a message to the base station if present. This tamper can be reset by replacing a smoke or heat detector in its mounting.

The unit may be placed in a "transit mode" when units are being shipped by key presses on the pair and test buttons e.g. holding down the pair button and pressing the test button three times. This ensures that power from the battery is not used up when not required. When it is required to activate a unit after shipping all that is required is to holding down the pair button and pressing the test button three times.

The "transit" mode will also disable radio communications allowing the units to be safely transported by aircraft if required.

A unit may be placed again in the transit mode if it is required to return the unit or ship the unit to another site.

Each unit will be able to indicate visually that it is powered and functioning in order to allow a user to distinguish between a working unit and dead unit. In some embodiments of the invention each unit will have a green LED light, known as the "Alive" LED, that will flash periodically to indicate that the unit is functioning.

Each firepoint unit comprises a latching call point 550. The latching call point will latch into a pressed condition and visually indicate that it has been pressed. A latching call point can be reset only using a special tool. Any activated call point which has not been mechanically reset after the fire alarm has ended will enter a chirp' mode in which the siren of that particular unit will periodically sound. This is to remind system users that the call point(s) in question needs to be reset before it can be used to manually raise the fire alarm.

Unit numbers may be set over a radio link from a base station. This allows greater system flexibility and reusability and obviates the need to open the unit for access.

Each unit will comprise local logs which may be used for debug and warranty purposes.

Base units will retain event logs for all units. Each unit will have sufficient non-volatile memory to allow logging data for at least a complete year to be retained. This will allow false alarms to be investigated and also provide details applicable to warranty claims as it will be possible to identify when a unit has been opened, activated or reconfigured.

After an internal tamper it will be possible to identify who, or at least which user has reset the internal tamper.

In systems comprising a base station unit, it will be possible to allow a user to enter telephone numbers via a navigation button keypad in order that text messages can be sent from the base station to any of a number of telephone numbers without the need to activate a fire alarm.

Each unit may be adapted to meet all relevant legislation in the region in which the IS system is being used. At present, all units meet all relevant UK and European legislation including: BS EN54-3, 5, 7, 11, 18 and 25; BS EN 50130-4; Set out below is further information relating to the setting up and usage of a system 2 illustrated in Figure 1.

Starting and joining a site network Starting a network Each unit has a guaranteed unique S2bit number. When the first two units are paired, which is initiated via button presses, the units arbitrate to decide which of the two unique numbers will become the site code.

Joining a network Subsequent units will be added to the network by holding / pressing the PAIR buttons on the units. When pairing with an existing firepoint or detector unit the new unit added to the system will take both the unique site code and unit number of the unit it is being paired with.

Base station units have additional functionality to allow the unit number to be adjusted prior to pairing.

Joining messages are not relayed to other units in the network and may also use lower transmit powers to limit the transmission range.

Raising the alarm F i repo I nt Pressing any installed call point in the system will activate the local Sounder and broadcast a radio message to be picked up by other installed units on the site. There is no delay between activating the call point and the radio message being transmitted, other than that imposed by the communication method outlined above.

Heat I Smoke Detectors When a heat or smoke alarm is triggered the unit will itself not sound. It will transmit a radio message to all other units in the same way as the firepoint above.

Cancelling a fire alarm After activation the firepoints will sound for 30 minutes before automatically resetting.

Fire alarms will also be able to be cancelled from any call point which has already been pressed by resetting the call point with its key. The alarm will not be resettable from a non-activated call point.

Any units with activated call points after either automatic reset or manual reset will periodically sound (e.g. 1 seconds every 10 minutes) to alert users the call point buttons need resetting.

It will not be possible to reset a fire alarm from any detector (smoke or heat).

The alarm can be reset by the base station via a PIN code protected function.

Tampers As mentioned above, there are three different types of tamper, internal, back and detector.

Internal tamper This is activated when the unit housing is opened and as an internal tamper is considered to potentially prevent the unit working and can only be reset using an electronic key on a tamper reset header or tablet PC via USB by an authorised person.

The tamper reset key could allow the ID of the person who has sealed the unit to be stored in the unit. Following reset the unit will provide a 30 second grace period to allow the unit lid to be correctly closed and secured before re-arming.

In the tamper state the unit will indicate a tamper fault and send a radio message to a OSM base station, if fitted as part of the system.

Back tamper The back tamper is intended to indicate when a unit has been removed from the wall/ceiling it was fixed to. Removing a unit from the wall/ceiling is not expected to be an issue from a unit integrity viewpoint but could change its ability to communicate to other units as it may be moved out of range. The unit will indicate a tamper fault on its own indicator and send a radio message to a GSM base station, if fitted as part of the system.

When the unit is fixed in place again the unit will check it can still satisfactorily communicate with another system component. If successful it will clear the tamper, if not it will indicate a radio link problem.

Detector tamper The presence of the detector head (smoke or heat) will be monitored. If the head is removed the unit will indicate a tamper fault on its own indicator and send a radio message to a GSM base station, if fitted as part of the system. The tamper fault will be cleared when the head is replaced.

Unit numbering so The unit number is only relevant to users who have an optional base station' unit which indicates which unit(s) has been activated and which can also send alerts via SMS text message to a number of designated people. All units will have a default unit number of 1.

The system will allow a number of units with the same unit number to allow end user flexibility. For example, all units in one area could be numbered the same allowing a fire incident to highlight a particular area of a building(s); equally all units can be numbered differently to allow identification of the exact unit which raised the alarm.

Programming the unit number incorrectly will not prevent an alarm being raised but would make locating the triggering unit difficult.

Silent Tests Turning now to Figures 9 and 10, the silent test function will be described in more detaiL Figure 9 illustrates a unit 4 forming part of an emergency system 20 and comprising a microprocessor 505 comprising an A to D converter. The unit 4 may comprise any one of the devices 30, 300 or 400, for example. If the silent test mode is activated in a parUcular unit 4, then a transceiver 910 will send and receive silent test messages, and on reception of signals will measure incoming signal strength.

The microcontroller 505 is operatively connected to tamper switches 915 and the unit's battery 920.

The device further comprises a display 925 which in this embodiment comprises a plurality of LED5.

Turning now to Figure 10, the silent test procedure is shown schematically. Step 1 is indicated by box lOOt The first stage is for a user to press and hold the silent test button 900 on any particular unit in order to initiate the silent test procedure, Next, as shown in box 1002, a silent test message is transmitted to other units 4 in the system 2 using a similar radio mechanism to that used when an alarm message is sent out.

As shown in box 1003, if a unit has not heard the silent test message it will continue to indicate a quiescent state as indicated by the LED display 925.

On the other hand, as shown at box 1004, If a unit does hear the silent test message, it will check the strength of the received signal.

If the received signal strength is not sufficiently above a predetermined level such as a noise floor or an attenuation reserve threshold, the silent test message is discarded, and the LED display will remain in the quiescent state as shown in box 1005.

On the other hand, if the received signal strength is sufficiently above the predetermined level, then the unit receiving the signal will check its warning inputs to, for example, check that there has been no tampering. This is shown in box 1006.

If no warning exists on the particular unit, it will indicate a silent test pass on the LED display 925.

On the other hand, if one or more warnings exist on a unit it will indicate on the LED display 925 that the silent test has failed.

Once the silent test has been carried out, a user may walk around all the units in the system and check the indication shown on each of the LED display 925, as shown in box 1009.

If all units show that the silent test has been passed, then the system as a whole is considered to have passed the silent test, as shown in box 1010.

On the other hand, if any of the units are showing anything other than silent pass on their respective LED display 925, the system as a whole is considered to have failed the silent test as shown at box 1015.

As described above, a silent test function is incorporated into each unit whose purpose it is to exercise the radio communication part of the units and provide visual confirmation that the unit is able to communicate successfully with other units on the same site. The silent test is initiated from any unit via a press on the silent test button. The unit sends out a silent message (i.e. no Sounder) activation which flashes the alarm LED on each unit which has successfully received and relayed the radio message. The site can then be inspected to check that each and every unit has received the message and that separate islands of units have not been inadvertently created by moving units or by the changing nature of construction sites.

The unit battery capacity has been sized to permit a silent test per week although the actual frequency of this will be determined by the construction site fire officer.

System Components Firepoint(FP1) In this embodiment a firepoint unit is wall mounted, battery powered unit consisting of sounder and call point communicating to other components in the same system via radio intended for indoor and outdoor use within a construction environment. The intended use of the Firepoint is to raise a fire alarm locally and on other radio inked firepoints within the same system when its call point is activated.

Battery pack The unit will utilise a battery pack made up of twelve alkaline C cell batteries in a 4 series, 3 parallel combination to provide a 6V, 23Ah battery pack with a polarised connector. The connector is polarised and additionally the electronics directly after the battery will protect against reverse polarity causing damage, no error will be indicated in the reverse polarity condition.

When not in an alarm condition the battery voltage will be checked periodically. If the remaining battery capacity is less than 30 days of normal operation an alarm will be indicated on the unit by flashing the low battery' LED and transmitting a low battery message to be indicated by a base station if it is part of the system. Battery monitoring may need to be temperature compensated to give a more accurate capacity indication over the full unit temperature range.

Sounder The Sounder will be driven from a switched mode power supply to ensure its power supply is consistent over the complete range of anticipated battery voltages.

Call point The firepoint will utilise a call point, rated to at least IP33C, with a two wire output from an electrical pushbutton within the unit. The output is normally open and when the call point is pushed to raise a fire alarm the contacts are then closed. The call point itself is a direct action, type A call point, which locks into the pressed state which is indicated by a flag in the call point window. The call point can be reset using a plastic key.

Antenna The antenna for radio communication will extend from the top surface of the unit. The antenna is fixed from within the enclosure and cannot be removed from the outside. The antenna will be flexible to reduce the possibility of damage.

LED Indicators The unit will contain three LED indicators, red, amber and green. Due to the nature of the unit these will be visible when directly in front of the unit but may not be visible from all angles.

The LEDS are labelled with their primary functionalIty when installed on site and in use, they are used for other purposes when pairing and silent testing where the labelling will be inconsistent.

The green LED, may be labelled Active', and may periodically flash to indicate that the unit is powered and functioning. To conserve power this LED will illuminate for 10 milliseconds every 5 seconds.

The red LED, may be labelled Alarm', and may indicate a fire alarm. The same red LED may be used for silent tests and will be on for 10 seconds every second to indicate a silent test is in progress.

The amber LED, labelled Fault' will be used to indicate unit faults such as low battery, low signal and tamper. These faults may have the following pattern (10 ins on 250 ms off x n) with a 2 seconds gap between groups. This will give a single, double, triple, quadruple etc flash group to indicate which particular type of fault is active. Where two faults are simultaneously active the highest priority fault will be displayed. Unit tampered' is considered the highest priority, then no radio signal', low radio signal' and low battery'.

Buttons There will two membrane pushbuttons, labelled A' and B' on the front face of the unit.

These are used to add units to the system, initiate a silent test and also together to enter a shipping mode.' Enclosure The enclosure will provide at least IP33C protection and will contain all of the unit components. There will be a tamper switch on the inside of the unit to indicate that the unit has been opened by an unauthorised user.

The enclosure lid will be secured to the main body of the unit with 4 Pozidriv /F'hillips screws.

The enclosure will be wall mounted using two M4 pan head screws, one on either side of the unit. These will be exposed when the unit is installed.

ComDonent mounting The Firepoint should be installed so that its call point is 1,4m above finished floor level.

As the Firepoint is a combined unit with a sounder this means that the sounder will be at a level of approximately 1.Sm above finished floor level, there does not appear to a location requirement for sounders.

Smoke! Heat Detector (SDI!HDI) This may comprise a battery powered unit. The main unit will power and monitor the detector. The unit is intended for indoor use only.

The unit needs to conform to EN54-7/5 and EN54-25.

Battery Dack The same battery pack as the Firepoint will be used.

Antenna The antenna for radio communication will be fixed from the inside of the unit and extend downwards from the unit when mounted on the ceiling, it cannot be removed from the outside, The antenna will be flexible to reduce the possibility of damage.

LED Indication LED indication will be the same as for the Firepoint.

Buttons Same as Firepoint Enclosure The enclosure will provide at least IP22C protection and will contain all of the unit components.

There will be a tamper switch on the inside of the unit to indicate that the unit has been opened by an unauthorised user.

Component mountinci The unit will be ceiling mpunted using 2 M4 pan head screws through the integral mounting points.

Base Station (BSI) The base station is an optional indoor only unit used to identify which unit(s) has been activated and to send out a fire alarm message via SMS (internal GSM modem and antenna) to up to six separate mobile telephone numbers.

Battery pack The same battery pack as the Firepoint will be used.

Audible alert The base station will give an audible alert to notify users that it has received a fire alarm.

Where multiple alarms are received within quick succession the user will be able to scroll up and down through a list of recently activated alarms.

The base station will also show alarms from units which are indicating other wamings such as low battery, unit tamper, or poor radio signal. Units with no radio signal will not be indicated.

Antenna The antenna for radio communication will extend from the top surface of the unit. The antenna is fixed from within the enclosure and cannot be removed from the outside.

LED Indicators These will be the same as for the Firepoint and Detector units.

Buttons Same as the Firepoint and Detector Units with the addition of a 5 button navigation pad for accessing information and changing settings.

Display The base station will incorporate a 4 line LCD display. This will only be active when an alarm or other message has been received. The rest of the time the display will be blank to conserve battery power.

The fascia will provide some impact protection for the display.

Enclosure The enclosure will provide at least IP22C protection and will contain all of the unit components. There will be a tamper switch on the inside of the unit to indicate that the unit has been opened. (The tamper message may be relayed to a base station if one is present).

The enclosure will be wall mounted using two M4 pan head screws, one on either side of the unit.

Component mounting The unit will be wall mounted. There appears to be no specified mounting locations or heights for this unit.

As has been mentioned hereinabove, an important feature of the invention as claimed in embodiments of the invention is that each unit in the system may be housed within substantially the same first housing component which is housed particularly the electronics and/or firmware. Each component may also have the same electronics/firmware, but the behaviour of the unit may be determined by means of a connection between the fascia and the first housing component.

A further advantage of this is that the inside of each first housing component will look substantially the same regardless of whether the unit is to be a base station, firepoint etc. Figure 11 shows a typical layout for the inside of a unit forming part of the system 2.

Figure 11 shows the inside of the first housing component 90. It can be seen that the first housing component 90, which has been described hereinabove.

In particular, the first housing component 90 houses the battery pack 510 which is held in position by battery straps 91.

The electronic components are arranged on a main electronics board 94. The main electronics board 94 comprises the second connector 96 which connects to the first connector formed in the fascia (second housing component). A connector 98 connects the battery back 510 to the main electronics board 94.

The unit also comprises a radio daughterboard 100 having an antenna connection 110 for connecting to the antenna 32. The antenna is connected to the first housing component 90 by means of a securing nut 120. The housing component 90 also comprises an antenna ground plane 130.

The unit also comprises a back tamper switch cable and connector 140, a tamper reset connection 150, an internal tamper switch 160, a USB connector 170 and a connector for the base station electronics 180.

Turning now to Figures 12 to 17, further details of how the first and second connectors engage with one another is shown in more detail.

In a particular embodiment of the invention, the fascia 92 comprises a first connector in the form of a ribbon cable connector 200 having a number of individual connectors numbered 20 to 21 in Figure 12. Each of these connectors is connectable with a corresponding connector forming part of the second connector 96. The number of connectors present on the first connector may be varied so that not all of the connectors of the second connector engage with a connector on the first connector. This means that the electronics components that are active will vary depending on the connections made.

It is thus possible to determine the behaviour/performance of a unit by ensuring appropriate connections.

Although the requirements of various British Standards such as EN54 have been referred to within this specification, it is to be understood that the Standards to which the system may have to adhere may change from time to time. In addition, in countries outside the UK different Standards may have to be met.

Claims (28)

1. CLAIMS1. A wireless emergency system comprising a plurality of units, each unit comprising a transceiver adapted to transmit and receive data to/from other units in the system, each unit comprising a tester comprising a transmitter adapted to transmit a silent message to other units in the system, and an indicator adapted to indicate to a user that a unit has received the silent message and that the strength of the signal received is above a predetermined level.
2. 2. A wireless emergency system according to Claim 1 wherein each unit comprises a delayer for delaying transmission of data by a predetermined randomised delay time, and a clear channel assessment for checking that no other unit within range of the unit in question is transmitting at that time.
3. 3. A system according to Claim 1 operating in the radio frequency bandwidth.
4. 4. A system according to any one of the preceding claims comprising a history buffer.
5. 5. A system according to any one of the preceding claims wherein the transceiver comprises a Wake On Radio component.
6. 6. A system according to any one of the preceding claims wherein each unit comprises a microprocessor for controlling operation of the unit.
7. 7. A system according to any one of the preceding claims wherein each unit comprises a monitor for monitoring the signal strength of transmitted and/or received data.
8. 8. A system according to any one of the preceding claims wherein each unit comprises an attenuation reserve threshold corresponding to the predetermined level.
9. 9. A system according to any one of the preceding claims wherein each unit comprises a fault warning unit.
10. 10. A system according to any one of the preceding claims comprising a firepoint system, wherein at least one unit comprises a firepoint device, and at least one other unit comprises a detector unit adapted to detect smoke and/or heat.
11. 11 A system according to any one of the preceding claims comprising a base unit, which base unit comprises an identifier adapted to identify which of the one or more units forming the system has been activated.
12. 12. A system according to any one of the preceding claims comprising an activation alarm for indicating when a unit has been manually activated.
13. 13. A system according to Claim 12 wherein the activation alarm comprises an audible signal.
14. 14. A system according to any one of the preceding claims wherein each unit comprises a transit mode in which the unit is placed into a low power state.
15. 15. A system according to any one of the preceding claims wherein each unit comprises a back tamper component.
16. 16. A system according to Claim 11 wherein the base station comprises an internal GSM modem and antenna.
17. 17. A system according to any one of the Claims 11 to 16 wherein the base station comprises a display unit.
18. 18. A system according to any one of the preceding claims wherein each unit comprises a first housing component adapted to receive and contain electronics and/or firmware, and a second housing compartment comprising a first connector for connecting to the electronics and/or firmware.
19. 19. A system according to Claim 18 wherein the first housing component of each unit comprises a second connector operatively connected to the electronics and/or firmware, which second connector is adapted to engage with the first connector.
20. 20. A system according to any one of Claims 18 and 19 wherein the second housing component comprises a fascia adapted to engage with the first housing component to form a closed housing.
21. 21. A unit forming part of a system according to any one of the preceding claims.
22. 22. An emergency system comprising a plurality of units, each unit comprising a housing having a first housing component adapted to receive and contain electronics and/or firmware, and a second housing component engageable with the first housing component to form a closed housing, the second housing component comprising a first connector for connecting to the electronics and/or firmware.
23. 23. An emergency system according to Claim 22 wherein each unit comprises substantially the same housing and electronics and/or firmware.
24. 24. A method of testing a wireless emergency system comprising a plurality of units, each unit comprising a transceiver adapted to transmit and receive data to/from other units in the system, the method comprising the steps of: causing one of the units to transmit a message to other units in the system; checking that all other units in the system have received the message and checking that the strength of each signal received is above a predetermined level.
25. 25. A method according to Claim 24 comprising the steps of: setting an attenuation reserve threshold; checking that the received signals are above the attenuation threshold.
26. 26. A system substantially as hereinbefore described with reference to the accompanying drawings.
27. 27. A unit substantially as hereinbefore described with reference to the accompanying drawings.
28. 28. A method substantially as hereinbefore described with reference to the accompanying drawings.