CA2192759C - A communication system - Google Patents

Abstract

A communication system (1) provides a wireless path for transmission of alarm signals from subscriber alarms systems (2) to monitoring stations (4) without transmission of a telephony signal from the alarm systems (2). No modification of the monitoring station (4) is required as the system (1) generates the telephony signal which the monitoring station expects to receive, even though only a trigger signal is transmitted. The system (1) may be used with a wide variety of different existing subscriber alarm systems (2) by appropriate connection of terminals on an interface (5) to conductors in the control panel of the subscriber alarm system (2). An acknowledgement is transmitted back as a "MIN Page" to the interface (5).

Description

"A Co nication-system and ~ethod for Alarm Signal~

~ACKGROUND OF THE INvENTION

Field o~ the Invention The in~e~tion relate~ to a communication system for communication of alar~ information from subscriber alarm systems to monitoring ~tations.

Prior Art Discussion In many presently a~ailahle subscriber alarm systems various sensor~ are conneeted to a control unit which activates audio and visual outputs and transmits an aLarm ~ignal to a ~onitoring station when an alarm condition arises. The signal is either a land-based or a wireless telephony signal. The format u~ed 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 man~ different types of subscriber alarm sy~tems and central monit~ring stations. Accordingly, ~any different formats are used for data transfer to the monitoring stations.

A basic problem which arise~ 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, thu~
breaking the ~onnection to the monitoring ~tation. The obvious ~olution to overcome this problem is to uxe ~5 ~ireles~ communication ~uch a~ a cellular mobile telephone network to communicate with the ~onitoring station.
Indeed, such an approach has been proposed in ~e~eral documents including EP632635, US5004999, JP6253042 and US4993059. In the sys~em described in VS4993059 there is a conventional dial-up land-ba~ed path for communication 2 1 ~ 2 7 ~ 9 with a monitoring ~tation. The alarm ~ystem incl~des detection circuitry which detects a failure of this path and then uses a redundant path via a cellular tran~eiver.
The first outgoing transmi~sion includes only the mobile identification num~er (MIN) and a serial number for the transceiver. This establishes ~i-directional communication with the monitoring station via the cellular system in the conventional manner for voice communication.

Howe~er, with both land-ba~ed and ~ireless communication, the alarm system may have difficulty in establishing an ef fective telephony connec~ion to the monitorin~ station becau~e the telephony network or the monitoring station may be excessively busy or becau~e of a fault in the telephony net~ork. A still further problem i~ the delay often associated with establishing telephony connections.
Thus, with increasing sophistication of alarm sen~ors and subscriber alarm systems it is increasingly the ca~e that the telephony connection to the monitoring station is the ~weakest link" in the alarm system.

A further problem is that existing alarms ~y~te~s which are de~igned for land-based communication may not be easily modified for wireless communication. Further, the system described in US~9930S9 requires use of detection circuitry to monitor all stage~ of the land-based communication path and activate the cellular c~mmunication if this path fails. This cir~uitry adds to complexity Indeed, in general, provi~ion of wireles~ co~munication circuits in the subscriber alarm system is expensive, thus limiting spread of their u6e.

Ob~ect6 of the Inventlon The invention i~ therefore directed toward~ providing a communication ~y~tem and method for wireless communication 21 9275't bet~een suh~criber alarm sy~tems and monitoring stations in a manner which avoids the abo~e-mentioned proble~s.

Summary of the In~ention The invention provides a comm~nication ~ystem comprising:-a plurality of sub~criber alarm system interfaces, each c~mpri~ing:-control means for detecting an alarm condition in a subscriber alarm ~stem; and a wirele~s transmitter comprising means for automatically trans~itting an alan~ trigger signal when an alarm condition is detected, said trigger signal including an alarm ~ystem identifier;

a message processing center associated with a plurality of interfaces and comprising:-a recei~er for receiving trigger alarm signals, a tran~mitter for transmitting telephony signals, and a controller compri~ing:-means for reading a received trigger slgnal, means for generating an emulation telephony signal which an as~o~iated monitoring station expects to receive directly from the alanm sy~tèm, and means for directing the tran~mitter to transmit the emulation telephony s ignal to ~aid monitoring station.

The invention also provides a method of co~munic~ting an alarm signal from a subscriber alarm system to a ~onitoring station, the method compri~ing the ~teps of:-detecting an alarm condition at the subscriber alarm S system;

transmitting an alarm trigger signal in response to detection of an alarm condition, said trigger signnl including an identifier for the s~bscriber alarm system;

receiving the trigger ~ignal and, in response, generating an emulation telephony signal which the monitoring station expects to receive directly from the subsc~iber alarm system; and transmitting said emulation telephony signal to said monitorinq station.

The invention therefore pro~ides a very simple solution to the problem of applying wireles~ communication technology to existing alarm systems and monitoring stations. The monitoring station recei~es the sign~l 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 i~ reyuired is a trigger ~ignal containing an alarm ~y~tem identifier. This avoid~
the expen~e and possible delay and congestion problems which can arise if a telephony ~ignal is generated at the ~ub~ribers' end.

n one embodiment, said controller comprises a stored ~atabase of records each s~oring emul~tion data for an associated alarm system, and means for generating said telephony ~ignal ac~ording to ~aid emulation data. The 2l ~275q databa~e record may store an address of the monitoring station associated with the alarm system. These features allo~ centralified updating, ~ithout the need for programming emula~ion data at the subscriber's end -either initially or for subsequent updates. It also allo~s the trigger signal to be very short.

In one e~bodiment, said wireles~ tran~mitter is a cellular transceiver comprising means for transmltting the trigger signal in an overhead control channel. This is a very well e~tabli~hed and effective ~echanism, which may be easily applied to transmission of a t~igger signal Preferably, the interface control mean~ comprises means for detecting an alanm condition status and for directing transmission of condition status data in the ESN frame of the overhead control channel, and said message proces~ing center ~ontroller comprises means for representing said status data in the telephony ~ignal. This allows comprehensive information to be received by the monitoring station - although ~nly a trigger 6ignal is transmitted from the subs~riber~s end.

Preferably, the message processing center comprise~ means for transmitting an acknowledgement signal to the interface in response to receipt of an acknowledge~ent signal fro~ the monitoring station. This allows validation by the interface and re-transmission if necessary In one embodiment, the wirele~ tra~smitter is a cellular tran~cei~er, and the message pr~cessing ~enter compri~es means for causing 8 cellular paging signal to be transmitt~d to the tr~n~ceiver as an acknowledgement.
Thi~ is a very si~ple way of tran~mitting an acknowledgement signal.

In one embodiment:-the interface control mean~ comprises means for directing the wireless transmi~ter to 1nclude emulation data in the trigger signal, and the mes~age processing ~enter ~ontroller comprise~
means ~or reading the emulati~n data in a received trigger signal and generating the telephony ~ignal according to ~aid emulation data. In the latter embodiment, said interface control meang may comprl~e means for directing the wirele~ transmitter to include the associated monitoring station address in the trigger signal, and the me~sage processing center compri~es means for reading ~aid address In a preferred embodiment, the me~sage processing center controller comprises means for crea~ing 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 pro~ides an alarm c~mmunication system comprising:-a plurality of subscriber alarm ~y~tem interfaces, each compri~ing:-control means for detecting an alarm condition in a subscriber alarm sy~tem; and a wireless transmitter compri~ing mean~ for automatically tran~mitting an alarm trigger ~ignal w~en an alarm c~ndition i~ detected, said trigger signal including an alarm ~y~tem identifier; and 21 ~27Sq a message processing center associated with a pl~rality of interfaces and comprising:-a recei~er for receiving trigger alarm signals, a tran~mitter for transmittin~ telephony signals, S and a controller comprising:-means for reading a received trigger signal to determine the alarm system identifier;

means for retrie~ing a database record associated with said alar~ sy6tem using baid identifier as an address;

means for reading emulation data in the retrieved database record and for using fiaid emulation data to generate an emulation telephony signal which an associated monitoring station expects to receive directly from the alarm 8y6tem; and means for reading the data~ase record to determine the associated monitoring station address and transmitting the emulation telephony signal to said monitoring station.

Ideally, the interface further compri~es a wireless recei~er 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 ackno~ledgement signal to the interface after receipt cf an acknowledgement from Lhe monitoring station. In one embodiment, the interface comprises means for recognising a dial-~ack (attempted communication) within a pre-set time period as an acknowledge~ent signal.
This is a very simple way of receiving an acknowledgement because it eliminate~ the need to process an S acknowledgement signal and the circuitry required to do so .

~he interface preferably comprises a wlreless transceiver such as a cellular transceiver, which items are readily a~ailable and inexpensive and allow use of a ceLlular system to be used to transmit the ala~m trigger signal to the message processing center.

Pre~erably, the ~ireless tran~mitter comprises means for trans~itting the trigger signal in an overhead control channel of a mobile teleco. Inication6 network. Such channels are not sub~ect to net~ork delays and congestion, and the need for voice channel capability in the transceiver is avoided. This al~o allows very fa~t transmission of the trigger signal.

Ideally~ the detecting means of the interface comprises input ports for connection to alarm si~nal conductors of an existing alanm system whereby the interface may ~e easily retro-fitted to an exi~ting alarm system. Ideally, the detecting means comprise~ a number of di~ferent types of input ports to allow retro-fitting t~ one of a range of di~ferent types of alarm syatems. Thu~, a ~ingle univer~al inter~ace may be developed which may be used with different types of ~u~scriber alarms systems different input ports being used in different cases.

In one embod~ment, the interface comprise~- means for capturing status data relating to the alarm condition and ~or transmitting said status data in the trigger signa~, and wherein said message proce~ing center cont~oller 21 ~2759 comprises means for representing said ~tatus data in the emulation telephony signal. Preferably, the wireless transmitter comprises a cellular tran6cei~er, and the control means compri~e~ means for directing insertion of said ~tatus data in the ~SN frame of an o~erhead control channel trigger s iynal.

In one embodiment, the me~sage processing center compri~es means for creating a database record for an interface, being addressable by an identifier o~ the interface, means for receiving emulation data from an installer via a telecomm~nications network and for wri~ing the emulation data to the record, and means for tran~mitting an activation signal to the interface after wrLting the emulation data. Thi~ allows initialisation of a particular interface in a ~ery 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 trigyer signal is received, for writing the emulation data to the event 2~ record, and for using content~ of the e~ent record to direct generation of the e~ulation sign~l. Use of an event record in this way allows simplified control of a particular alarm signal.

In one emhodiment, the interface compri~es a mean~ for transmitting alarm ~tatus data with the additional alarm signal and the controller comprises a means for writing the alarm status data to the e~ent record.

In one embodiment, the c~ntroller comprises a gateway processox controlling the receiver, a dialling processor controlling the tranæmitter, and a main processor, each proces~or comprising means for perfon~ing an action with reference to the event record and passing control over to 2 ! 92759 a next processor. Thi~ mechanism allows distribution of the proces~ing tasks at the message processing center in a simple and effective ~anner to achieve a very fast message transfer rate in real time.

Pre~erably, the processors pa88 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 allo~s a large degree of processor-independence.

In one embodiment, the controller comprises a main processor, a plu~ali~y of modular gateway processors connected ~o as~ociated communication de~ices in the receiver, and a plurality of modular dialler processors connected to as~ociated cc. Inication devices in the trans~itter. Thi~ allow~ 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 ~ain 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 embodLment, the invention provides an alarm communications mes~age proce~sing center comprising:-a gateway process~r comprising ~eans for receiving an alarm trigger signal including an i~entif ier of an associated sub~criber alarm syste~;

2 1 92 I Sq ~eans for creating an in-process e~ent record uniquely associated with the received trigger signal and means for writing ~aid identifier to said event record;

a main processor comprising means for reading the identifier from the event record, for ~etrieving a database record addressed by the identifier, and writing emulation data and a monitoring station address read from the database record to th~ in-proce5s event record and a dialling processor comprising mean~ for reading the emulation data and the monitoring ~tation 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 ~ignal to the monitoring station.

According to a furthe~ aspect, the invention provides an alarm communication sy~tem compri~ing:-a subscriber alarm ~ystem 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 ~ignal including an 2S alarm system identifier when an alarm condition i~
detected, said trigger signal being transmitted in an overhead control channel; and a mes~age proce~ing center as~ociated with a plurality ~f interfaces and comprising:-21 ~2159 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 rece~ved trigger signal to determine the alarm syRtem identifier;

means for retrieving a database record associated with said alarm system using ~ai~
identifier as an address;

means for reading em~lation 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 addre~s and for transmitting the emulation telephony signal to said monitoring station According to another aspect, the invention providex an ala~m communication system comprising:-a plurality of subscriber alarm system interfaces, each comprising: -a wireles~ transmitter and . ~

control ~eans comprising means for detecting an alarm condition in a subscriber alarm syste~, storage means for storing telephony emulation data and an address of an ass~ciated monitoring S station, and mean~ for directing the wireless transmitter to transmit a trigger ~ignal including an alarm system identifier, the emulation data, and the monitoring station add~ess; and a message processing center associated w~th a plurality 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 received trigger signal, for using the emulation data to generate an emulation telephony ~ignal which the addressed monitoring station expects to recei~e directly from the alarm sy~tem, an~ for directing the tran~mitter to trans~it the ~0 telephony to the addres~ed 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 su~scriber alarm system;

transmitting an alarm trigger signal in response to detection o~ an alarm condition, said trigger signal 21 9275~

including an identifier for the subscriber alarm sy~tem, telephony em~lation datar and monitoring station address;

recei~ing the triyger signal and, in response, using the emulation data to generate an emulation telephony signal which the addressed monitorin~ station expects to receive from the alarm system, and transmitting the telephony signal to the addre66ed moni~oring ~tAt3on.

DETAILE~ DESCRIPTION OF THE INVEN~ION

Brief descri~tion of the drawings The in~ention will ~e more clearly understood from the following de~cription of ~ome embodiments thereof, gi~en by way of example only with reference to the accompanying drawing~ in which:-Fig 1 i~ schematic overview of a communication ~yste~
of the invention;

Figs 2a and 2b are a ~chematic representation of an interface of the communication system;

Fig 3 is a diagram illustrating a me~sage processing center of the system in more detail; and Fig 4a and 4b are toyether a flow chart illustratingoperati~n of the system.

Detailed description of the emdodiments Renferring initially to Fig 1, there id 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, and 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 sy~tem, but is utilised by the interface 5 and the message processing center ~ of the system l to transfer messages in one ~'leg~ of the path B.
The network used is the Cellemetry Sy~tem described in United States Patent Specification Nos. US 5546444 and US
5526401 (BellSouth Corporation) in which forward and re~erse control channel~ are used.

The message processing center 8 emulat~s the fiubscrlber alarm system 2 and generates emulation signals which are identical to those which are transmitted on path ~, and transmits them via the PSTN 9 to the ~onitoring station 4.
Thi6 is performed by retrieving emulation data from a database record (pennanent record) u~ing the subscriber alarm system identifier in the trigger signal to index the record.

Thus, the monitoring station 4 "~ees" identical signal~ 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 i~ alway~ used ~o that the monitoring station 4 al~ays receives a signal, even if the dial-up path A ha~ failed by, for example, a burglar cutting telephone wlres, or communicatlons problems. Thus, the monitoring station 4 either receives two identical signals from the two ro~tes, or only receives the ~ignal from the path B, this being the signal which it expects to receive from path A.

Of cour~e, the ~ubscriber alarm system's circuits for the conventional path may be disabled ~o 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 21 9275~

transmission of telephony signals f~om the subscriber's end in a manner transparent to the monitoring station.

The ~essage processing center 8 receives an acknowledgement ~ignal from the monitoring station, and in turn send~ an acknowledgement to the interface 5. This acknowledgement is a page signal which is simply recognised by the interface, not proces~ed.

Because the message processing ~enter 8 emulates conventional telephony signals, there i8 no need for any modification of the monitoring station 4. Further, because the interface 5 merely detect~ an alarm condit~on in the su~scriber alarm system 2, it may be easily retro-fitted 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 ~e~sage processing center 8 comprises a receiver 10 compriRing a number of modular gateway modem bays for receiving signals from the Celle~etry System gateway computer~. A transmitter 12 for trans~ission of telephony ~ignals has a number of modular dialler mode~ bays. The center 8 also compri~es 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 trans~itter 12.

Referring now to Fig~ 2a and 2b, there i~ illustrated an interface circu-t 20 forming part of the interface 5. The interface circuit 20 has te inAls 22 and 23 for connectlon in parallel with the sounder of a subscriber alarm system, usually an electronic siren or bell. The optically isolated output of these terminals i~ connected to an interrupt input of a microprocessor 34 for analysis of the nature of the signals. This allows the interface 2 ! 92 75~

5 to distinguish between burglary and fire alerts. ~n 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 con~erter circuit 29 to be used. The circuit 29 is connected to a port on the microprocessor 34. This allow~ detailed information to be captured, such as hold-up medical alarm conditions. Terminal~ 2~
connected to the transceiver receive analog ~perating information such a~ control channel signal strength. The circuit 20 also comprises æerial interface terminals 35 for capture of comprehensive information from a subscriber alarm system which has a ~erial link. The circuit 29 comprises ports P00 to P07 conne~ted to the microprocessor 34, used to generate voltages for analog to digital con~ersion~

The circui~ 20 is connected to a cellemetry transceiver using the CMM RXD and CMM Txn terminals, also indicated by the numerals 31 and 32, The tran6ceiver i~ of the type marketed a~ a Cellemetry Radio Transceiver - a cellular radio unit with only control channel circuitry. A CMM RTS
terminal 33 is u~ed for handshake/flow control. These ~erminal~ are ~onnected 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 terminal~ 31 doe~ not include ~oice channels - only circuits sufficient to transmit a trigger signal on a forward or reverse overhead control channel ~hich i~ conventionally used for mobile telephone roamer registration. It i~ thus inexpensive and compact.

It will be apparent from the description of the interface 5 that it may be easily retro-fitted to existing subscrl~er alarm systems by simply connecting up the relevant terminals, depending on the nature of the subscriber alarm syste~. An example is a ~imple 4-~ire connection having two wires for power and two for an alarm output conductor. The interface chip 24 is programmed to recognise a wide ~ariety o~ inputs and to in t~rn cause the microprocessor 34 to i.nitiate an additlonal alnrm s~gnal transmitted over-the air to be picked up by the Celle~etry System.

Referring now to Fig 3, the message proces~ing center B i~
illustrated in more detail. The center 8 comprises a local area network 40 which interconnecta various processing devices. ~he receiver 10 comprises a numbe~
of modular bays of modems progra~med for communication with gateway computers of a cellular system. Each bay lO
is controlled by a gateway control proces~or (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~
al~o forming part of the controller ll. The controller 11 is completed ~y a main control processor (MCP) 43 ~nd 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 ~
comprises a set of dialogue line interfaces 47, each controlled by an IVR PC 48.

In operation, interfaces 5 a~e tested and assigned unique mobile identity numbers (MIN), which are recorded on a database on the server 45. ~his record is indexed by the MIN number. Each interface i8 then connected to a subscriber alarm ~y~tem by connection of the re}e~ant terminal~, depending on the nature of the alarm system.
This is a ~ery si~ple operation.

The interface i8 then activ~ted in real time by one of the I~R computer~ 48. The installer dials in to the IVR PC 48 S and transmits data needed by the CMPC 8 to send emulation signals. This is perfor~ed interactively ~y keying data in respon~e to IVR PC prompts using D~MF tones. The emulation data includes details of the mapping of digital dialler messages to send in the case of each activation l~ report type. These are identical to the messages which are conventionally transmitted by the alar~ ~ystem to the monitoring station ~ia the dial-up path. The IVR PC
writes this information t~ the per~anent re~ord.

~he interface ~ then tran~mits a trigger signal (fir~t time activation registration) t~ confirm radio functionality and pro~ides de~ails of operations and program status to the center 8. ~he permanent record i~
~pdated when this registration is received. ~he in~taller then trigger~ a test alarm and the center relays the alarm to the monitoring ~t~tion and verifies this to indicate successful completion of the installation.

An i~portant aspect of the ~nvention i~ the fact that the interface 5 tran8mits only a trigger - not a telephony . signal. In this embodiment, the trigger uses a conventional forward or rever~e cellular overhead control channel for registration of a mobile telephone to register its location This channel is not ~ubject to delays or congeStion, unlike the telephony ~hannels.

Referring now to ~ig~ 4a and 4b, operation of the system l to handle an alarm æignal is now deæcri~ed. This method is indicated generally by the numeral 60. In step 61, an alarm condition i~ detected by an interface S and ~his causes the transmitter of the interface 5 to emit a trigger signal ~cellular regifitration signal). This includes the MIN number of the interface and a 32-bit data field ~hich inciudes the alarm status information. This data i~ within the frame reserved for the ESN number in a conventional regi~tration signal. The leading 3 bit~
indicate the nature of the remaining bits. The data generally include~ codes indicating the nature of the ala~m condition, and po~sibly diagnostic information indicating ho~ the ~ystem 2 is operating. This signal is picked up hy the Cellemetry System 6 and is routed via a gateway computer to the message processing center 8. The recei~er 10 is the only mean~ of contact ~etween the sub~criber alarm system and the message processing center 8. In the center 8, a GCP 41 controls the gateway modem whi~h receives the tri~ger signal and it initiates an event wh~c~ 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 t~o points, the event i~ processed by referen~e to an in-pr~cess event (IPE) record. This record is used by the GCP 4I, t~e MCP
43 and the DCP 42. The IP~ record i~ a temporary record which is created and e~entually logged in real time when the ~ignals have been handled.

A~ indicated by the step 62, the gate~ay computer dials into the message proces~ing center 8 and if the trigger ~ignal is not valid, a~ indic~ted by the step~ 63 and 64 the relevant GCP 41 generates an exception log record. It al80 generates a respon~e to the gate~ay computer with rele~ant error code and hang-up information.

If the trigger signal is validr in step 65 the GCP 41 creates an event by creating an IPE record in an IP~
table. This record contains all of the data supplied by the gateway computer for the registration and the current time is added hy the GCP 41, ~arking 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 21 9275C~

-- 2:~ --I PE RECORD
Field Narne 7~peS~z~ EdJ't Rlmor~
(B~rcs) 1 Eventld ~ lS GCP Sequencc ~o. - Same as uscd in his~oncal Evenl~og.

2 Event Start Tir,nc @ GCP Date/Tirne stamp on rccord creation by 3 GCP Bay Reg r 2 ~CP Bay 9~ ot GCP.

4 l(iateway I`lanle C 8 GCP ~ame o~ gatew~y rrescn~ message.

Gal~way Id ~ 2 GCP Catew3y recunl #
6 aat~way Time C 6 GCP Tunc field of actual message scllt by galcWay 7 Gateway Ml~ C 10 GCP t ; e MlN.
8 Gateway ESr~ C 8 GCP 1~ g ESN 8 chars or he~ dig~ts (~nns status).

9 Galcway SID C 4 GC~ 1 ' O mc~sage c ;~, " 3 SID.

10 Gateway MSC C 2 GCP l~lSC id.
11 DCPBay ~ 2 MCP DCP bag àssi~ned by l~CP to contact 3 ~) MS.

12 CSPhoneNo ~1 10 MCP Phone no. Or MS.

13 CSMa~sFvl~dt ~ 2 MCP ~ormat to use in MS ~ logu~
14 CSMsg Data C 2~ MCP ~hat to send to MS.
1~; CSRetries C 1 MC~ How many times has the MS call bcen llied?

IG CSMsgRcsult N 2 DCP Delivered OK? PR Errot code.
17 DiallcrNo N 2 DCP Dialler # assigDcd by DCP to call CS.

21 '~275~

1~ GCPBayPage 1~1 2 MCP CCP Bay N~ lo rcqucsl Ml~l page.

I9 MIMageRetr~s C 1 ~CP H~wmany lim~s h~ gatew~y Ml~l page requc5~ bce~ ~ried ?

20 I~ JPageResulls 1`~ 2 GCP Deli-~ered OK? OR error codc.

21 GCPModeml~o N 2 GCP GCP Modcm Nc. uscd lo c~ll g~teway.

22 EYenlEndTim~ (~) MCP Date~Time slamp event pr~
cu...~!~l 1.
23 Owncr C 5 All ~he p.ocessor currently r~s for event p~x Note: MS - monitoring ~tation N - numeric C - characters (alph~n ~ric) An important aspect of ~peration of the center 8 is that control of the event is transferred between the different processors by a~endment 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 e~tablish if the registration is to be processed. If so, it retrieve~ emulation data from the permanent record and writes it to the IP~ record. ~he emulation data includes the monitoring station phone number, message f~rmat, the ~ubscriber's account number, the message data to transmit (e.g. ~orrelating a message with an alarm statu~ code in the recei~ed ~SN data), and number of retrie~. The MCP 43 then selects an appropriate DCP bay and mark~ the record for that bay. This is a function ~f the ~n-line ~tatu~ and num~er of idle dialler~
3~i for each bay. These ~;tep3 are indica~ed by the numerals 67 and 7t) in Fig 4a.

- 21 ~2759 When a DCP 42 identifies a new IPE record marked for its attention, it assigns one of its free diallers to transmit the mes~age to the monitoring station. This i~ achieved ~y fiimply reading the e~ulation data of the IPE record and ~uild~ng an emulation ~ignal according to this data in a con~entional manner. ~his ~ignal includes all of the status information deri~ed from the ESN frame and i~ thus very comprehensive.

This step is indicated by the numeral 71 in Fig 4a (in which the dialler ba~ is referred to as a 'Smart Dialler" ) . In step 72, the DCP 42 update~ the monitoring station report result field. If the deli~ery failed, the MCP 43 moves the IPE record to the historical event log file and generates an event error record. At thi~ point, the current time is added b~ the MCP 43, thu~ marking the end-of-event time stamp.

If, however, the delivery was succe6~ful, the MCP 43 marks the IPE record for the most appropriate GCP bay as follows:-- If the GCP which received the regi~tration i~
still on-line, thi~ i~ u~ed. It may ~till be connec~ed to/our receiving a new registration from the required gateway.

- Otherwise, the GCP with the most idle modems i~
chosen.

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

The GCP 41 re~uests the gateway to "MIN page" the originating interface as an acknowledgement. This iS
recognised by the interface 5 as 8 delivery confirmation.

There is no bi-directional communication - simply reco~nition 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 S transfers contr~l back to the MCP 43. The microproces~or 34 of the interface 5 is programmed to auto~atically re-~ransmit the trigger signal if the acknowledgement is not received with a pre-set time.

The MCP 43 then moves the IPE record to the hi~torical message event log file and adds the c~rrent 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 8~. If delivery i~ 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 modulàr nature of the CMPC c~ntroller 11, namely the mod~lar GCPs 41, the MCP 43, and the modular DCPs 42 allow for dlstribution of tasks very effectively. This helps to achieve effective and fast throughput of messages in real ti~e, de~pite the fact that there may be hundreds of messages being handled simultaneously. The IPE record is a very simple and ef~ective way o~ achieving control using such modular processors. Another feature which helps coordination is the fac~ that the proce~sors automatically update a watchdog field in a table in real-time. If a particular bay fails, the MCP 43 i -'iately re-assignS
the rele~ant task.

It will be appreciated that the invention provides a system which once installed can be used for any subscri~er system which dials a monitoring station to non-intrusively and transparently pro~ide a second alarm signal path, which is m~re 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 ~o the ~ubscriber alarm system, and no modification ~hatsoever is required of the ~onitoring station because of the emulation which take~ place. It S will also be appreciated that message~ are handled in real time very e~ficiently within the message processing center 8 by the manner in which an IP~ 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. F~rther, the system may be installed very inexpensively for sub8cribers. Thi~ i~ because a transce~ver which only handles trigger signals such as control channels is much le~s expensiYe than a conventional wireless transceiver Further, the control and detectlon circuits of the interface 5 are relati~ely simple, inexpensive, and easy to connect to a ~ubscriber alarm system. Tn addition, the power supply requirement is very low.

It is envi~aged that the trigger 6ignal 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 ~e~age proce~sing center need not ha~e a stored database of permanent records storing em~lation data or monitoring ~tation addre~ses. It would ~imply read the data in the received trigger signal and use it for emulation and transmission of the telephony signal. S~ch a message processing center may create and use in-process e~ent records, much as de~cribed aboue The emulation data and the address w~uld be written im~ediately to the e~ent ~ecord instead of being retrieved from a database.

Claims (28)

1. 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 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 telephony signal to the monitoring station.

2. A system as claimed in claim 1, wherein 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.

3. A system as claimed in claim 2, wherein each database record stores an address of the monitoring station associated with the alarm system.

4. A system as claimed in claim 1, wherein said wireless transmitter is a cellular transceiver comprising means for transmitting the trigger signal in an overhead control channel.

5. A system as claimed in claim 4, wherein 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.

6. A system as claimed in claim 1, wherein 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.

7. A system as claimed in claim 6, wherein 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.

8. A system as claimed in claim 1, wherein:

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.

9. A system as claimed in claim 8, wherein said interface control means comprises 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.

10. A system as claimed in claim 8, wherein 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.

11. 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 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 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.

12. A system as claimed in claim 11 wherein 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.

13. A system as claimed in claim 11 wherein the interface comprises means for recognising a connection attempt within a pre-set time period as an acknowledgement signal.

14. A system as claimed in claim 12 wherein the interface comprises a cellular transceiver.

15. A system as claimed in claim 11, wherein the wireless transmitter comprises means for transmitting the trigger signal in an overhead control channel of a cellular system.

16. A system as claimed in Claim 11 wherein 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.

17. A system as claimed in 16 wherein the detecting means comprises a plurality of different types of input ports, whereby the interface may be retro-fitted to one of a range of different types of alarm system.

18. A system as claimed in claim 11, wherein 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.

19. A system as claimed in claim 18, wherein 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.

20. A system as claimed in claim 11 wherein the message processing center comprises:
means for creating a database record for an interface, addressable by an identifier of the interface;
means for receiving emulation data from an installer via a telecommunications network and writing the emulation data to the database record, and means for transmitting an activation signal to the interface after writing the emulation data to the database record.

21. A system as claimed in claim 11, wherein 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 generate the emulation signal.

22. A system as claimed in claim 11 wherein 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 generate the emulation signal, and wherein the interface comprises means for transmitting alarm status data with the trigger signal and the controller comprises means for writing said alarm status data to the event record.

23. A system as claimed in claim 11 wherein 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 generate the emulation signal, and wherein 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.

24. A system as claimed in claim 11 wherein 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 far using contents of the event record to generate the emulation signal, and wherein 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 means for updating an owner field in the event record to pass over control to a next processor.

25. A system as claimed in claim 11 wherein 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.

26. A system as claimed in claim 25, wherein the gateway processors and the dialler processors comprise means for automatically updating a watchdog field in a table in real time to indicate processing status and the controller comprises a main controller comprising means for re-assigning tasks when gateway or dialler processors fail.

27. 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:
a receiver 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 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 for transmitting the emulation telephony signal to said monitoring station.

28. 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 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 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.