IES80475B2 - A message processing centre - Google Patents

Description

A Message Processing Centre The invention relates to a communication system for communication of alarm information from subscriber alarm a systems to monitoring stations.

In many presently available subscriber alarm systems various sensors are connected to a control unit which activates audio and visual outputs and transmits an alarm signal to a monitoring station when an alarm condition arises. The signal is either a land-based or a wireless telephony signal. The format used depends on the nature of the subscriber alarm system and also on the nature of the monitoring station. In any one country there are generally many different types of subscriber alarm systems and central monitoring stations. Accordingly, many different formats are used for data transfer to the monitoring stations .

A basic problem which arises when the telephony signal is transmitted via a land-based PSTN network is that burglars can often gain access to the cables and cut them, thus breaking the connection to the monitoring station. The obvious solution to overcome this problem is to use wireless communication such as a cellular mobile telephone network to communicate with the monitoring station.

Indeed, such an approach has been proposed in several documents including EP632635, US5004999, JP6253042 and US4993059. In the system described in US4993059 there is a conventional dial-up land-based path for communication S8047S with a monitoring station. The alarm system includes detection circuitry which detects a failure of this path and then uses a redundant path via a cellular transceiver. «» 5 The first outgoing transmission includes only the mobile identification number (MIN) and a serial number for the transceiver. This establishes bi-directional communication with the monitoring station via the cellular system in the conventional manner for voice communication. 10 However, with both land-based and wireless communication, the alarm system may have difficulty in establishing an effective telephony connection to the monitoring station because the telephony network or the monitoring station may be excessively busy or because of a fault in the 15 telephony network. A still further problem is the delay often associated with establishing telephony connections. Thus, with increasing sophistication of alarm sensors and subscriber alarm systems it is increasingly the case that the telephony connection to the monitoring station is the weakest link in the alarm system. 20 A further problem is that existing alarms systems which are designed for land-based communication may not be easily modified for wireless communication. Further, the 25 system described in US4993059 requires use of detection circuitry to monitor all stages of the land-based communication path and activate the cellular communication if this path fails. This circuitry adds to complexity. Indeed, in general, provision of wireless communication circuits in the subscriber alarm system is expensive, thus limiting spread of their use. 30 The invention is therefore directed towards providing a communication system and method for wireless communication between subscriber alarm systems and monitoring stations in a manner which avoids the above-mentioned problems.

The invention provides a communication system comprising:a plurality of subscriber alarm system interfaces, each comprising :control means for detecting an alarm condition in a subscriber alarm system; and a wireless transmitter comprising means for automatically transmitting an alarm trigger signal when an alarm condition is detected, said trigger signal including an alarm system identifier; a message processing center associated with a plurality of interfaces and comprising:a receiver for receiving trigger alarm signals, a transmitter for transmitting telephony signals, and a controller comprising:means for reading a received trigger signal, means for generating an emulation telephony signal which an associated monitoring station expects to receive directly from the alarm system, and means for directing the transmitter to transmit the emulation telephony signal to said monitoring station.

The invention also provides a method of communicating an alarm signal from a subscriber alarm system to a monitoring station, the method comprising the steps of:detecting an alarm condition at the subscriber alarm system; transmitting an alarm trigger signal in response to detection of an alarm condition, said trigger signal including an identifier for the subscriber alarm system; receiving the trigger signal and, in response, generating an emulation telephony signal which the monitoring station expects to receive directly from the subscriber alarm system; and transmitting said emulation telephony signal to said monitoring station.

The invention therefore provides a very simple solution to the problem of applying wireless communication technology to existing alarm systems and monitoring stations. The monitoring station receives the signal it expects to receive, namely a conventional telephony signal. However, at the subscriber end there is no need to generate a telephony signal. All that is required is a trigger signal containing an alarm system identifier. This avoids the expense and possible delay and congestion problems which can arise if a telephony signal is generated at the subscribers' end.

In one embodiment, said controller comprises a stored database of records each storing emulation data for an associated alarm system, and means for generating said telephony signal according to said emulation data. The database record may store an address of the monitoring station associated with the alarm system. These features allow centralised updating, without the need for programming emulation data at the subscriber's end either initially or for subsequent updates. It also allows the trigger signal to be very short.

In one embodiment, said wireless transmitter is a cellular transceiver comprising means for transmitting the trigger signal in an overhead control channel. This is a very well established and effective mechanism, which may be easily applied to transmission of a trigger signal.

Preferably, the interface control means comprises means for detecting an alarm condition status and for directing transmission of condition status data in the ESN frame of the overhead control channel, and said message processing center controller comprises means for representing said status data in the telephony signal. This allows comprehensive information to be received by the monitoring station - although only a trigger signal is transmitted from the subscriber's end.

Preferably, the message processing center comprises means for transmitting an acknowledgement signal to the interface in response to receipt of an acknowledgement signal from the monitoring station. This allows validation by the interface and re-transmission if necessary.

In one embodiment, the wireless transmitter is a cellular transceiver, and the message processing center comprises means for causing a cellular paging signal to be transmitted to the transceiver as an acknowledgement. This is a very simple way of transmitting an acknowledgement signal.

In one embodiment:the interface control means comprises means for directing the wireless transmitter to include emulation data in the trigger signal, and the message processing center controller comprises means for reading the emulation data in a received trigger signal and generating the telephony signal according to said emulation data. In the latter embodiment, said interface control means may comprise means for directing the wireless transmitter to include the associated monitoring station address in the trigger signal, and the message processing center comprises means for reading said address.

In a preferred embodiment, the message processing center controller comprises means for creating an in-process event record when a trigger signal is received, for writing emulation data to said event record, and for using contents of the event record to generate the emulation signal.

According to another aspect, the invention provides an alarm communication system comprising:a plurality of subscriber alarm system interfaces, each comprising:control means for detecting an alarm condition in a subscriber alarm system; and a wireless transmitter comprising means for automatically transmitting an alarm trigger signal when an alarm condition is detected, said trigger signal including an alarm system identifier; and a message processing center associated with a plurality of interfaces and comprisingsa receiver for receiving trigger alarm signals, a transmitter for transmitting telephony signals, and a controller comprising:means for reading a received trigger signal to determine the alarm system identifier; means for retrieving a database record associated with said alarm system using said identifier as an address; means for reading emulation data in the retrieved database record and for using said emulation data to generate an emulation telephony signal which an associated monitoring station expects to receive directly from the alarm system; and means for reading the database record to determine the associated monitoring station address and transmitting the emulation telephony signal to said monitoring station.

Ideally, the interface further comprises a wireless receiver and means for recognising an acknowledgement signal from the message processing center, and the message processing center controller comprises means for directing transfer of said acknowledgement signal to the interface after receipt of an acknowledgement from the monitoring station. In one embodiment, the interface comprises means for recognising a dial-back (attempted communication) within a pre-set time period as an acknowledgement signal. This is a very simple way of receiving an acknowledgement because it eliminates the need to process an acknowledgement signal and the circuitry required to do so.

The interface preferably comprises a wireless transceiver such as a cellular transceiver, which items are readily available and inexpensive and allow use of a cellular system to be used to transmit the alarm trigger signal to the message processing center.

Preferably, the wireless transmitter comprises means for transmitting the trigger signal in an overhead control channel of a mobile telecommunications network. Such channels are not subject to network delays and congestion, and the need for voice channel capability in the transceiver is avoided. This also allows very fast transmission of the trigger signal.

Ideally, the detecting means of the interface comprises input ports for connection to alarm signal conductors of an existing alarm system whereby the interface may be easily retro-fitted to an existing alarm system. Ideally, the detecting means comprises a number of different types of input ports to allow retro-fitting to one of a range of different types of alarm systems. Thus, a single universal interface may be developed which may be used with different types of subscriber alarms systems different input ports being used in different cases.

In one embodiment, the interface comprises means for capturing status data relating to the alarm condition and for transmitting said status data in the trigger signal, and wherein said message processing center controller comprises means for representing said status data in the emulation telephony signal. Preferably, the wireless transmitter comprises a cellular transceiver, and the control means comprises means for directing insertion of said status data in the ESN frame of an overhead control channel trigger signal.

In one embodiment, the message processing center comprises means for creating a database record for an interface, being addressable by an identifier of the interface, means for receiving emulation data from an installer via a telecommunications network and for writing the emulation data to the record, and means for transmitting an activation signal to the interface after writing the emulation data. This allows initialisation of a particular interface in a very simple manner in which the integrity of the database record is also assured.

In one embodiment, the controller comprises means for creating an in-process event record when a trigger signal is received, for writing the emulation data to the event record, and for using contents of the event record to direct generation of the emulation signal. Use of an event record in this way allows simplified control of a particular alarm signal.

In one embodiment, the interface comprises a means for transmitting alarm status data with the additional alarm signal and the controller comprises a means for writing the alarm status data to the event record.

In one embodiment, the controller comprises a gateway processor controlling the receiver, a dialling processor controlling the transmitter, and a main processor, each processor comprising means for performing an action with reference to the event record and passing control over to a next processor. This mechanism allows distribution of the processing tasks at the message processing center in a simple and effective manner to achieve a very fast message transfer rate in real time.

Preferably, the processors pass control over to a next processor by updating an owner field in the event record. This is a very simple way of passing control and allows a large degree of processor-independence.

In one embodiment, the controller comprises a main processor, a plurality of modular gateway processors connected to associated communication devices in the receiver, and a plurality of modular dialler processors connected to associated communication devices in the transmitter. This allows very simple growth of the message processing center without affecting the current capability of the center. It also allows redundancy very important for alarm communication.

Preferably, the gateway and dialler processors update a watchdog field in a table to indicate current status, and the main controller re-assigns processors upon failure by reference to the watchdog field. This is a very simple way of maintaining controller integrity.

According to another embodiment, the invention provides an alarm communications message processing center comprising :a gateway processor comprising means for receiving an alarm trigger signal including an identifier of an associated subscriber alarm system; means for creating an in-process event record uniquely associated with the received trigger signal and means for writing said identifier to said event record; a main processor comprising means for reading the identifier from the event record, for retrieving a database record addressed by the identifier, and writing emulation data and a monitoring station address read from the database record to the in-process event record; and a dialling processor comprising means for reading the emulation data and the monitoring station identifier from the in-process event record and for automatically generating an emulation telephony signal which the monitoring station expects to receive directly from the subscriber alarm system, and for transmitting said emulation signal to the monitoring station.

According to a further aspect, the invention provides an alarm communication system comprising:a subscriber alarm system interface comprising:control means for detecting an alarm condition in a subscriber alarm system, and a cellular transceiver connected to the control means and comprising means for automatically transmitting an alarm trigger signal including an alarm system identifier when an alarm condition is detected, said trigger signal being transmitted in an overhead control channel; and a message processing center associated with a plurality of interfaces and comprising:12 a receiver having means for receiving alarm trigger signals from a cellular system; a transmitter for transmitting telephony signals; and a controller comprising:means for reading a received trigger signal to determine the alarm system identifier; means for retrieving a database record associated with said alarm system using said identifier as an address; means for reading emulation data in the retrieved record and for using said emulation data to generate an emulation telephony signal which an associated monitoring station expects to receive directly from the alarm system; and means for reading the record to determine the associated monitoring station address and for transmitting the emulation telephony signal to said monitoring station.

According to another aspect, the invention provides an alarm communication system comprising:a plurality of subscriber alarm system interfaces, each comprising:a wireless transmitter; and control means comprising means for detecting an alarm condition in a subscriber alarm system, storage means for storing telephony emulation data and an address of an associated monitoring station, and means for directing the wireless transmitter to transmit a trigger signal including an alarm system identifier, the emulation data, and the monitoring station address; and a message processing center associated with a plurality 10 of interfaces, and comprising:a receiver for receiving alarm trigger signals; a transmitter for transmitting telephony signals; and a controller comprising means for reading a 15 received trigger signal, for using the emulation data to generate an emulation telephony signal which the addressed monitoring station expects to receive directly from the alarm system, and for directing the transmitter to transmit the telephony to the addressed monitoring station address.

In another aspect, the invention provides a method of communicating an alarm signal from a subscriber alarm system to a monitoring station, the method comprising the steps of:detecting an alarm condition at the subscriber alarm system; transmitting an alarm trigger signal in response to detection of an alarm condition, said trigger signal including an identifier for the subscriber alarm system, telephony emulation data, and monitoring station address; receiving the trigger signal and, in response, using 5 the emulation data to generate an emulation telephony signal which the addressed monitoring station expects to receive from the alarm system, and transmitting the telephony signal to the addressed monitoring station.

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:15 Fig 1 is schematic overview of a communication system of the invention; Figs 2a and 2b are a schematic representation of an interface of the communication system; Fig 3 is a diagram illustrating a message processing 20 center of the system in more detail; and Fig 4a and 4b are together a flow chart illustrating operation of the system.

Referring initially to Fig 1, there is shown a communication system 1 of the invention. The system 1 is shown for use with a particular subscriber alarm system 2 which communicates via a PSTN network 3 with a monitoring station 4 administered by the alarm company of which the subscriber is a client. For simplicity, the system 1 is shown for use with a single subscriber alarm system 2 and a single monitoring station 4, however, in practice it will be used for in the range of tens of thousands to millions of subscriber alarm systems 2 and with up to thousands of monitoring stations 4. Indeed, an advantage of the system 1 is that it can be used for any subscriber alarm system and with any monitoring station.

The conventional path for transmission of an alarm signal is indicated by the letter A in Fig 1. The communication system 1 of the invention provides an additional path B which is always used, irrespective of success of the conventional path. The additional path is started by an interface 5 which detects an alarm condition in the subscriber alarm system 2.

The interface 5 transmits a radio trigger signal which is picked up by a mobile telecommunications network 6 and relayed via gateway computers and a PSTN network 7 to a message processing center 8. The trigger signal is not a telephony signal. In general, it is any signal which can alert the center 8 and need only include an identifier for the subscriber alarm system 2. This avoids the problems which may arise when a telephony signal is used, namely possible faults, congestion-related delays, and slow speed. Indeed, it may be generated in as little as 100 ms - much quicker than a telephony signal. The network 6 does not form part of the system, but is utilised by the interface 5 and the message processing center 8 of the system 1 to transfer messages in one leg of the path B. The network used is the Cellemetry System described in United States Patent Specification Nos. US 5546444 and US 5526401 (BellSouth Corporation) in which forward and reverse control channels are used.

The message processing center 8 emulates the subscriber alarm system 2 and generates emulation signals which are identical to those which are transmitted on path A, and transmits them via the PSTN 9 to the monitoring station 4. This is performed by retrieving emulation data from a database record (permanent record) using the subscriber alarm system identifier in the trigger signal to index the record.

Thus, the monitoring station 4 sees identical signals to those which are received via the conventional route, and because they are received within a pre-set time period they are regarded as relating to the same alarm condition. The additional path is always used so that the monitoring station 4 always receives a signal, even if the dial-up path A has failed by, for example, a burglar cutting telephone wires, or communications problems. Thus, the monitoring station 4 either receives two identical signals from the two routes, or only receives the signal from the path B, this being the signal which it expects to receive from path A.

Of course, the subscriber alarm system's circuits for the conventional path may be disabled so that path B alone is relied upon. Indeed, the system 2 need not include any land-based communication circuits, the invention allowing a tamper-proof path to be used without the need for transmission of telephony signals from the subscriber's end in a manner transparent to the monitoring station.

The message processing center 8 receives an acknowledgement signal from the monitoring station, and in turn sends an acknowledgement to the interface 5. This acknowledgement is a page signal which is simply recognised by the interface, not processed.

Because the message processing center 8 emulates conventional telephony signals, there is no need for any modification of the monitoring station 4. Further, because the interface 5 merely detects an alarm condition in the subscriber alarm system 2, it may be easily retrofitted to the alarm system 2. Updates such as changes in monitoring stations may be made centrally at the center 8.

Referring again to Fig 1, the message processing center 8 comprises a receiver 10 comprising a number of modular gateway modem bays for receiving signals from the Cellemetry System gateway computers. A transmitter 12 for transmission of telephony signals has a number of modular dialler modem bays. The center 8 also comprises a controller which is in three parts, namely a main processor for primary control and coordination, a gateway processor for control of the receiver 10, and a dialler processor for control of the transmitter 12.

Referring now to Figs 2a and 2b, there is illustrated an interface circuit 20 forming part of the interface 5. The interface circuit 20 has terminals 22 and 23 for connection in parallel with the sounder of a subscriber alarm system, usually an electronic siren or bell. The optically isolated output of these terminals is connected to an interrupt input of a microprocessor 34 for analysis of the nature of the signals. This allows the interface to distinguish between burglary and fire alerts. In addition, the interface circuit 20 includes terminals 25, 26 and 27 for connection to trip channels or analog inputs. An interface chip 24 interfaces eight inputs to one output selected by a three-way address and it allows an analog to digital converter circuit 29 to be used. The circuit 29 is connected to a port on the microprocessor 34. This allows detailed information to be captured, such as hold-up medical alarm conditions. Terminals 28 connected to the transceiver receive analog operating information such as control channel signal strength. The circuit 20 also comprises serial interface terminals 35 for capture of comprehensive information from a subscriber alarm system which has a serial link. The circuit 29 comprises ports P00 to P07 connected to the microprocessor 34, used to generate voltages for analog to digital conversion.

The circuit 20 is connected to a cellemetry transceiver using the CMM RXD and CMM TXD terminals, also indicated by the numerals 31 and 32. The transceiver is of the type marketed as a Cellemetry Radio Transceiver - a cellular radio unit with only control channel circuitry. A CMM RTS terminal 33 is used for handshake/flow control. These terminals are connected to the microprocessor 34 which controls interfacing. LEDs 1-7 display system status to the installing technician in order to verify correct system operation.

The transceiver connected to the terminals 31 does not include voice channels - only circuits sufficient to transmit a trigger signal on a forward or reverse overhead control channel which is conventionally used for mobile telephone roamer registration. It is thus inexpensive and compact.

It will be apparent from the description of the interface 5 that it may be easily retro-fitted to existing subscriber alarm systems by simply connecting up the relevant terminals, depending on the nature of the subscriber alarm system. An example is a simple 4-wire connection having two wires for power and two for an alarm output conductor. The interface chip 24 is programmed to recognise a wide variety of inputs and to in turn cause the microprocessor 34 to initiate an additional alarm signal transmitted over-the air to be picked up by the Cellemetry System.

Referring now to Fig 3, the message processing center 8 is illustrated in more detail. The center 8 comprises a local area network 40 which interconnects various processing devices. The receiver 10 comprises a number of modular bays of modems programmed for communication with gateway computers of a cellular system. Each bay 10 is controlled by a gateway control processor (GCP) 41 forming part of the controller 11. The transmitter 12 comprises a number of modular dialler bays, each of which is controlled by a dialler control processor (DCP) 42, also forming part of the controller 11. The controller 11 is completed by a main control processor (MCP) 43 and a backup MCP 44. A database is provided by a primary NT server 45 mirrored by a back-up NT 46, each of which is connected to the network 40. Finally, the center 8 comprises a set of dialogue line interfaces 47, each controlled by an IVR PC 48.

In operation, interfaces 5 are tested and assigned unique mobile identity numbers (MIN), which are recorded on a database on the server 45. This record is indexed by the MIN number. Each interface is then connected to a subscriber alarm system by connection of the relevant terminals, depending on the nature of the alarm system. This is a very simple operation.

The interface is then activated in real time by one of the IVR computers 48. The installer dials in to the IVR PC 48 and transmits data needed by the CMPC 8 to send emulation signals. This is performed interactively by keying data in response to IVR PC prompts using DTMF tones. The emulation data includes details of the mapping of digital dialler messages to send in the case of each activation report type. These are identical to the messages which are conventionally transmitted by the alarm system to the monitoring station via the dial-up path. The IVR PC 48 writes this information to the permanent record.

The interface 5 then transmits a trigger signal (first time activation registration) to confirm radio functionality and provides details of operations and program status to the center 8. The permanent record is updated when this registration is received. The installer then triggers a test alarm and the center relays the alarm to the monitoring station and verifies this to indicate successful completion of the installation.

An important aspect of the invention is the fact that the interface 5 transmits only a trigger - not a telephony signal. In this embodiment, the trigger uses a conventional forward or reverse cellular overhead control channel for registration of a mobile telephone to register its location. This channel is not subject to delays or congestion, unlike the telephony channels.

Referring now to Figs 4a and 4b, operation of the system 1 to handle an alarm signal is now described. This method is indicated generally by the numeral 60. In step 61, an alarm condition is detected by an interface 5 and this causes the transmitter of the interface 5 to emit a trigger signal (cellular registration signal). This includes the MIN number of the interface and a 32-bit data field which includes the alarm status information. This data is within the frame reserved for the ESN number in a conventional registration signal. The leading 3 bits indicate the nature of the remaining bits. The data generally includes codes indicating the nature of the alarm condition, and possibly diagnostic information indicating how the system 2 is operating. This signal is picked up by the Cellemetry System 6 and is routed via a gateway computer to the message processing center 8. The receiver 10 is the only means of contact between the subscriber alarm system and the message processing center 8. In the center 8, a GCP 41 controls the gateway modem which receives the trigger signal and it initiates an event which begins with receipt of a valid trigger (registration data packet) from the cellular system gateway computer and ends with writing of an event record to an event log table. Between these two points, the event is processed by reference to an in-process event (IPE) record. This record is used by the GCP 41, the MCP 43 and the DCP 42. The IPE record is a temporary record which is created and eventually logged in real time when the signals have been handled.

As indicated by the step 62, the gateway computer dials into the message processing center 8 and if the trigger signal is not valid, as indicated by the steps 63 and 64 the relevant GCP 41 generates an exception log record. It also generates a response to the gateway computer with relevant error code and hang-up information.

If the trigger signal is valid, in step 65 the GCP 41 creates an event by creating an IPE record in an IPE table. This record contains all of the data supplied by the gateway computer for the registration and the current time is added by the GCP 41, marking a start-of-event time stamp. Importantly, the GCP 41 also marks an OWNER field as being the MCP 43. In more detail, the following sets out the structure of the IPE record in full.

IPE RECORD Field Name Type Size (Bytes) Edit Remarks 1 Eventld N 15 GCP Sequence No. - Same as used in historical Eventlog. 2 Event Start Time @ GCP Date/Time stamp on record creation by GCP. 3 GCP Bay Reg N 2 GCP Bay # of GCP. 4 IGateway Name C 8 GCP Name of gateway presenting message. 5 Gateway Id N 2 GCP Gateway record #. 6 Gateway Time C 6 GCP Time field of actual message sent by gateway. 7 Gateway MIN C 10 GCP Incoming MIN. 8 Gateway ESN c 8 GCP Incoming ESN 8 chars of hex. digits (alarms status). 9 Gateway SID c 4 GCP Incoming message originating SID. 10 Gateway MSC c 2 GCP MSC id. 11 DCPBay N 2 MCP DCP bay assigned by MCP to contact MS. 12 CSPhoneNo N 10 MCP Phone no. of MS. 13 CSMsgFormat N 2 MCP Format to use in MS dialogue. 14 CSMsg Data C 24 MCP What to send to MS. 15 CSRetries c 1 MCP How many limes has the MS call been tried? 16 CSMsgResult N 2 DCP Delivered OK? PR Error code. 17 DiallcrNo N 2 DCP Dialler # assigned by DCP Io call CS. 18 GCPBayPage N 2 MCP GCP Bay No. (o request MIN page. 19 MINPageRetrys C 1 MCP How many times has gateway MIN page request been tried ? 20 MINPageResulls N 2 GCP Delivered OK? OR error code. 21 GCPModcmNo N 2 GCP GCP Modem No. used to call gateway. 22 EventEndTime @ MCP Date/Tune stamp event processing completed. 23 Owner C 5 All The processor currently responsible for event processing.

Note: MS - monitoring station N - numeric C - characters (alphanumeric) An important aspect of operation of the center 8 is that control of the event is transferred between the different processors by amendment of the OWNER field in this manner. When the MCP 43 identifies a new IPE record marked for its attention in the IPE table, it looks up the file of permanent records to establish if the registration is to be processed. If so, it retrieves emulation data from the permanent record and writes it to the IPE record. The emulation data includes the monitoring station phone number, message format, the subscriber's account number, the message data to transmit (e.g. correlating a message with an alarm status code in the received ESN data), and number of retries. The MCP 43 then selects an appropriate DCP bay and marks the record for that bay. This is a function of the on-line status and number of idle diallers for each bay. These steps are indicated by the numerals 67 and 70 in Fig 4a.

When a DCP 42 identifies a new IPE record marked for its attention, it assigns one of its free diallers to transmit the message to the monitoring station. This is achieved by simply reading the emulation data of the IPE record and building an emulation signal according to this data in a conventional manner. This signal includes all of the status information derived from the ESN frame and is thus very comprehensive.

This step is indicated by the numeral 71 in Fig 4a (in which the dialler bay is referred to as a Smart Dialler). In step 72, the DCP 42 updates the monitoring station report result field. If the delivery failed, the MCP 43 moves the IPE record to the historical event log file and generates an event error record. At this point, the current time is added by the MCP 43, thus marking the end-of-event time stamp.

If, however, the delivery was successful, the MCP 43 marks the IPE record for the most appropriate GCP bay as follows:If the GCP which received the registration is still on-line, this is used. It may still be connected to/our receiving a new registration from the required gateway.

Otherwise, the GCP with the most idle modems is chosen.

These steps are indicated by the numeral 73 and 75 in Fig 4b.

The GCP 41 requests the gateway to MIN page the originating interface as an acknowledgement. This is recognised by the interface 5 as a delivery confirmation.

There is no bi-directional communication - simply recognition of the paging signal. This step is indicated by the numeral 76 and in step 77 the GCP 41 stores the result of the MIN page request in the IPE record and transfers control back to the MCP 43. The microprocessor 34 of the interface 5 is programmed to automatically retransmit the trigger signal if the acknowledgement is not received with a pre-set time.

The MCP 43 then moves the IPE record to the historical message event log file and adds the current time to the end-of-event time field as indicated by the step 79. The process 60 is then ended as indicated by the step 80. If delivery is unsuccessful as indicated by step 73 or the acknowledgement or confirmation MIN page operation is unsuccessful, an event error is generated in step 68.

The modular nature of the CMPC controller 11, namely the modular GCPs 41, the MCP 43, and the modular DCPs 42 allow for distribution of tasks very effectively. This helps to achieve effective and fast throughput of messages in real time, despite the fact that there may be hundreds of messages being handled simultaneously. The IPE record is a very simple and effective way of achieving control using such modular processors. Another feature which helps coordination is the fact that the processors automatically update a watchdog field in a table in real-time. If a particular bay fails, the MCP 43 immediately re-assigns the relevant task.

It will be appreciated that the invention provides a system which once installed can be used for any subscriber system which dials a monitoring station to non-intrusively and transparently provide a second alarm signal path, which is more secure than conventional paths. It is thus entirely flexible and versatile and may be very easily applied by installers. The interface unit may be very easily connected to the subscriber alarm system, and no modification whatsoever is required of the monitoring station because of the emulation which takes place. It will also be appreciated that messages are handled in real time very efficiently within the message processing center 8 by the manner in which an IPE record is created and managed. An important point is that the IPE record allows operation of the centre 8 to be independent of any single processor. This is very important for communication of alarm signals. Further, the system may be installed very inexpensively for subscribers. This is because a transceiver which only handles trigger signals such as control channels is much less expensive than a conventional wireless transceiver. Further, the control and detection circuits of the interface 5 are relatively simple, inexpensive, and easy to connect to a subscriber alarm system. In addition, the power supply reguirement is very low.

It is envisaged that the trigger signal may include the emulation and/or the address of the associated monitoring station. This may be the case if a cellular system having a control channel protocol allowing a relatively large data frame is used, for example. In this case the message processing center need not have a stored database of permanent records storing emulation data or monitoring station addresses. It would simply read the data in the received trigger signal and use it for emulation and transmission of the telephony signal. Such a message processing center may create and use in-process event records, much as described above. The emulation data and the address would be written immediately to the event record instead of being retrieved from a database.

Claims (1)

1. An alarm communications message processing centre comprising:a gateway processor comprising means for receiving an alarm trigger signal including an identifier of an associated subscriber alarm system; means for creating an in-process event record uniquely associated with the received trigger signal and means for writing said identifier to said event record; a main processor comprising means for reading the identifier from the event record, for retrieving a database record addressed by the identifier, and writing emulation data and a monitoring station address read from the database record to the inprocess event record; and a dialling processor comprising means for reading the emulation data and the monitoring station identifier from the in-process event record and for automatically generating an emulation telephony signal which the monitoring station expects to receive directly from the subscriber alarm system, and for transmitting said emulation signal to the monitoring station. A message processing centre as claimed in claim 1, wherein said gateway, main, and dialling processors each comprise means for passing control over to a next processor when a task is complete by writing a flag indicating the next processor to an owner field in the in-process event record. A message processing centre as claimed in claim 1, wherein the gateway and dialling processors each comprise a plurality of modular processors. A message processing centre as claimed in claim 3, wherein each of said modular processors comprises means for automatically updating a watchdog status field to indicate processing status and the main processor comprises means for re-assigning tasks in response to said field when gateway or dialling processors fail. A message processing centre substantially as described with reference to the accompanying drawings.