Improvements In Communications Links

Field of the invention

[001] This invention relates to improvements in communications links.

[002] The invention is applicable to communication systems generally, and will be described in relation to an alarm communication system such as described with reference to our co-pending international application PCT/AU2003/ 000921 (WO20004012434), the contents of which are incorporated herein by reference.

[003] The invention will be described in the context of a line monitoring arrangement, a communication terminal with a back-up communication arrangement, a communication system having a customer terminal with a back-up communication link, to an arrangement for enabling a customer terminal to establish communication, and to a method and arrangement for configuring a customer terminal. The customer terminal can be a remote terminal which is adapted to be connected to a supervision terminal via a communication link.

Background of the invention

[004] In many cases such as emergency communications and security communications, it is important to have a back-up communication link. For example, where an alarm system uses a land ^" line, the line can be cut and the communication link will be lost.

[005] There are a number of systems which seek to address this problem, and some of these are discussed in our above co-pending application.

[006] Any reference herein to known prior art does not, unless the contrary indication appears, constitute- an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application.

Summary of the invention

[007] The present invention provides a communication terminal adapted to transmit data via a back-up communication link when required.

[008] The present specification also describes an arrangement which allows a communication panel to monitor the communication link between an alarm panel and the communication panel.

[009] The specification also describes an arrangement which enables communication network settings to be entered into a communication panel without the need to use a computer terminal for this task.

[010] The specification also details a powering arrangement which enables the customer's broadband gateway modem to be powered during a mains outage by using the battery backed powering facilities of the communications panel.

[011] The invention also provides a means for detecting an alarm panel substitution attack.

[012] In one embodiment, the invention provides a system and method for providing a back-up communication link between one or more first terminals and at least one second terminal connectable by a first communication link, wherein: - the first terminal is adapted to transmit data to a second terminal via the first communication link; the second terminal being adapted to transmit a response message to the first terminal; the first terminal being adapted to monitor the first communication link to detect the response message; wherein, if the response message is not received within a first time-out time limit, the first terminal transmits the data to the second terminal via a second communication link.

[013] The system can include at least one gateway arranged to connect the first terminal to a communication network.

[014] The system can include two or more gateways each adapted to connect the first terminal to a communication network in which a first gateway is designated as a default gateway via which an initial attempt to access the communication network is made, and wherein each of the remaining gateways is prioritized to attempt to establish a connexion successively if the attempt via the higher priority gateway fails.

[015] The invention provides a system and method for providing a back-up communication link between one or more remote terminals and at least one supervision terminal connectable by a first communication link, including:- a remote terminal adapted to transmit data to a supervision terminal via the first communication link; the supervision terminal being adapted to transmit a response message to the remote terminal; the remote terminal being adapted to monitor the first communication link to detect the response message; wherein, if the response message is not received within a first time-out time limit, the remote terminal transmits the data to the supervision terminal via a second communication link.

[016] A further embodiment of the invention provides a back-up communication system and method for providing a back-up communication link path between a first terminal and a second terminal connectable by a first communication link and a second communication path, including:- a the first terminal being adapted to transmit data to a the second terminal via the first communication link; the second terminal being adapted to transmit a response message to the first terminal; the first terminal being adapted to monitor the first communication link path to detect the response message; wherein, the monitoring means being adapted to detect failure of the first communication path,

[017] the first terminal including first control means adapted to cause the first terminal to transmit the data to the second terminal via the second communication path if failure of the first communication path is detected.

[018] The failure of the first communication path can be detected by comparing the elapsed time following transmission of data from the first terminal with a permitted time window.

[019] The time window can be fixed.

[020] The time window can be automatically adjustable by a controller to allow for variable delay on the first communication path.

[021 ] The remote terminal can be adapted to re-transmit the data up to a predetermined number of times via the first communication link if the response is not received within a first time window less than the first time-out time limit.

[022] The remote terminal can be adapted to re-transmit the data one or more times via the second communication link if a response is not received via the second communication link within a second time window.

[023] The invention also provides a communication system including: - one or more remote terminals; one or more remote terminals associated with at least one of the supervision terminals; each remote terminal being connectable to its associated supervision terminal via a first communication path and being connectable to its associated supervision terminal via a second communication path; the remote terminal being adapted to detect the receipt of a polling signal from the supervision terminal via the first communication network; the remote terminal being adapted to transmit messages to the supervision terminal via the second communication path if the polling signal is not received within a time window.

[024] According to further embodiment of the invention there is provided a communication system including: - one or more remote terminals; one or more supervision terminals where each remote terminal is associated with at least one of the supervision terminals; each remote terminal being connected to its associated supervision terminal via a first communication path and via a second communication path; the remote terminal being adapted to detect the receipt of an acknowledgement signal from the supervision terminal when a first message has been transmitted to the supervision terminal from the remote terminal via the first communication network; the remote terminal being adapted to transmit the first

message via the second communication network if the acknowledgement signal is not received within a time window.

[025] The communication system can be a telemetry system.

[026] The second terminal can be a supervision terminal, and the first terminal can be a remote terminal.

[027] The first communication path can include a first communication network.

[028] The second communication path can include a wireless network.

[029] The invention can also be embodied in a method of providing a backup communication path between a remote terminal and a supervision terminal connectable via a first communication path and via a second communication path, the method including the steps of: monitoring the first communication path at the remote terminal for a signal from the supervision terminal; and, in the event that the expected signal does not arrive at the remote terminal, within a time window, sending messages from the remote terminal to the supervision terminal via the second communication path.

[030] The invention is also embodied in a remote terminal connectable to a supervision terminal via a first communication path and a second communication path, the remote terminal including monitor means adapted to detect an expected signal from the supervision terminal; the remote terminal being adapted to send messages to the supervision terminal via the second communication path in the event that the expected signal is not received within a time window.

[031 ] An embodiment of the invention includes : one or more second terminals corresponding to the supervision terminal; one or more first terminals, corresponding to the remote terminal, associated with at least one of the supervision terminals; a data network linking the supervision terminal and the remote terminal; wherein;

each remote terminal is connected to a first communication network and to a second communication network; wherein the second communication network is a wireless communication network; the remote terminal being adapted to detect the receipt of an acknowledgement signal from the supervision terminal when a first message has been transmitted to the supervision terminal from the remote terminal via the first communication network; the remote terminal being adapted to transmit the first message via the second communication network if the acknowledgement signal is not received within a time window.

[032] The invention also provides a line monitor arrangement to enable a communication terminal to verify the integrity of a communication link with a signalling transmitting device.

[033] The line monitor arrangement includes a signal generator transmitting a signal to the signalling device

[034] The signal generator and the signal detector are at one end of the communication link and the signal terminator is at the other end of the communication link.

[035] The signal generator can be associated with the communication terminal.

[036] The signal detector can be associated with the communication terminal.

[037] The signal terminator can be associated with the signalling transmitting device.

[038] The invention also provides a method of enabling the entry of set-up parameters into a terminal without the use of a computer.

[039] In one embodiment, the invention enables the entry of communication network settings into a communication terminal using a DTMF telephone.

[040] The invention provides a method of configuring a remote terminal using a DTMF signaller. In particular, a DTMF phone can be used to configure the remote terminal.

[041] Where the network uses fixed IP addresses, the remote terminal can be configured by the method of: connecting the remote terminal to a network; setting the remote terminal to configuration mode; connecting a DTMF phone to the signalling transmitting device connection of the remote terminal; entering the IP address via the DTMF phone; entering the subnet mask via the DTMF phone.

[042] Where the network includes a DHCP (Dynamic Host Configuration

Protocol) server, the remote terminal can be configured by the method of: connecting the remote terminal to a network; setting the remote terminal to configuration mode; connecting a DTMF phone to the signalling transmitting device connection of the remote terminal; using the DTMF phone to initiate a DHCP registration process.

[043] The DTMF phone can be used to select between the fixed IP address mode and the DHCP mode by entering a code which identifies the applicable mode.

[044] The Dynamic Host Configuration Protocol (DHCP) is an Internet protocol for automating the configuration of computers that use TCP/IP. DHCP can be used to automatically assign IP addresses, to deliver TCP/IP stack configuration parameters such as the subnet mask and default router, and to provide other configuration information such as the addresses for printer, time and news servers.

[045] The present invention is not limited in applicability to systems in which the remote terminal is a burglar alarm, although the high degree of security offered by the invention is particularly advantageous in this context. Other uses for the invention include remote monitoring of meters, for example electricity, gas or water meters, or remote monitoring of the status of an automatic vending machine.

Brief description of the drawings

[046] An embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[047] Figure 1 illustrates an alarm communication system in which an embodiment of the invention can be implemented;

[048] Figure 2 illustrates a communication terminal adapted to implement the present invention;

[049] Figure 3 is a signal flow diagram illustrating message transmission between a communication terminal and a monitor terminal to implement the back-up function;

[050] Figure 4 is a schematic illustration of a line monitor arrangement according to an embodiment of the invention;

[051] Figure 5 is a block schematic illustration of a terminal adapted to be configured in accordance with an embodiment of the invention;

[052] Figure 6 is a schematic illustration of a substitution attack where the primary burglar panel is replaced by a secondary burglar alarm panel;

[053] Figure 7 is a schematic illustration of an enhanced line monitor arrangement according to an embodiment of the invention;

[054] Figure 8 is a schematic illustration of an enhanced powering arrangement for the customer's broadband gateway modem which allows it to survive mains power outages;

Detailed description of the embodiment or embodiments

[055] The invention will be described with reference to the accompanying drawings.

[056] Figure 1 illustrates an alarm system according to an embodiment described in our co-pending application.

[057] A communication terminal or customer terminal 102 is interposed between a burglar alarm panel 104 and one or more of the agency terminals 122, 124. The customer terminals are connected via a first communication network, preferably a data network such as broadband network 116, and/or a second communication

network, such as wireless network 114 to the agency terminal(s). The agency terminals are connected to an automation system terminal 120 which receives alarm messages from and manages the agency terminals.

[058] The customer terminal 102 can also be connected to the automation system terminal 120 via the PSTN through dialler receiver 130.

[059] The customer terminal (102) can be a gateway providing communications for a plurality of devices, such as PC 110 and telephone 1083, at the customer premises. The customer terminal 102 and the agency terminals 122, 124 are adapted to provide transparent communication between the burglar alarm panel 104 and the automation system terminal 120.

[060] The customer terminal (102) can connect to the broadband network

(116) directly using an embedded broadband modem (xDSL, DOCSIS or WiMAX etc.) or one or more gateway devices (140). Having multiple gateways provides redundancy. Each gateway can be arranged to communicate over a respective communication link. In normal operation, a first gateway is designated as the default gateway. The Customer Terminal software is programmed to switch to the second gateway if an attempted access over the default gateway times out. The gateway addresses can be programmed into the subscriber equipment such as the customer terminal.

[061] Figure 2 illustrates a communication terminal 200 of the type suitable for use in the system of Figure 1. The burglar alarm panel 220 connects to an alarm panel interface 202 in the communication terminal 200. The alarm panel interface converts downstream signals into a format required by the alarm panel 220, and converts upstream signals originating from the alarm panel 220 into a format suitable for transmission over the communication network(s) to which the communication panel 200 is connected. The communication panel shown has a wireless modem 214, an ADSL modem 210, a telephone line interface 206, and an Ethernet interface 212. Where the alarm panel is a legacy system requiring PSTN signalling, the alarm panel interface 202 can emulate the required PSTN signalling to enable the alarm panel 220 to send alarm signals. The network processor 204 has a number of ports which can be used to send and receive communication signals. In this embodiment, the processor is programmed to respond to the detection of the failure of the first path which is

connected to the line 224 (or 212) to activate the port connected to wireless modem 214.

[062] The processor 204 can monitor the delay on the first path and adjust the time window for retransmission or switching to the second path in accordance with the monitored delay.

[063] Figure 3 illustrates the signals exchanged between the burglar alarm panel BA, the communication terminal CT, and the agency terminal AT in a first case, indicated the exchange of signals in dashed line box 321, and in a second case illustrated by the exchange of signals in dashed line box 331.

[064] The set of transactions labelled 321 demonstrate the operation of the system when one or more IP paths are functional. In this case the Burglar Alarm system sends an "event" notification to the Customer Terminal, which forwards it to the Agency Terminal over the IP path as "event - IP". The IP path can be carried on xDSL. The Agency Terminal returns an acknowledgement message "event acknowledge - IP" to the Customer Terminal over the same IP path. The Customer Terminal in turn sends the acknowledgement "event acknowledge" to the Burglar Alarm system in the format expected by the burglar alarm.

[065] In Figure 3, the vertical lines are the time axis. The maximum time allowed by the Customer Terminal for an acknowledgement message to be received in response to a transmitted event message over the IP path is shown as item 322 and is designated as tAiPMAX-

[066] If the acknowledgement message from the Agency Terminal indicating that the Agency Terminal has received the event message sent by the Customer Terminal is not received by the Customer Terminal in time t _A i _P MAX, the Customer Terminal resends the message over the IP path a pre-determined number of times, as shown in the set of transactions labelled 331.

[067] The set of transactions labelled 331 illustrate the operation of the ^' system when the IP path is malfunctioning. This could be a temporary malfunction that manifests itself by abnormally long message transmission times, or a complete failure of the IP link.

[068] As in the above case the Burglar Alarm system sends an event notification to the Customer Terminal, which forwards it to the Agency Terminal over

the IP path. In this case the Customer Terminal does not get an acknowledgement message from the Agency Terminal within a time interval of duration less than or equal to tAiP _MA X- As a result it resends the message and waits to receive the acknowledgement message. This is repeated a number of times. If the acknowledgement message has still not been received by the Customer Terminal over the EP path after a second time limit 332, the Customer Terminal sends the event notification to the Agency Terminal over the Cellular path illustrated as "Event - Cellular", using a number of message re-sends as for the IP path if required. The Agency Terminal returns an acknowledge message "event acknowledge - Cellular" to the Customer terminal over the Cellular path. The Customer Terminal then sends an "event acknowledge" message to the Burglar Alarm system.

[069] Some Burglar Alarm systems may, after waiting for a time interval

333, re-send the original event notification to the Customer Terminal as illustrated by the second "event" in box 331, in which case the Customer Terminal can be programmed to wait for the event retransmission by the Burglar Alarm system to be completed before sending the event acknowledge message to the Burglar Alarm system.

[070] This method thus uses the cellular link as a dynamic backup path to the primary IP link.

[071] The IP Gateway (140) arrangement shown in Figure 1 illustrates the manner in which the Customer Terminal (102) may implement path redundancy over the broadband IP connection. Internet connectivity at the customer's premises may be via one or more Gateway devices in which each gateway can correspond to a different access technology. For example, one Gateway (140) connects to the internet (115) using an xDSL modem, another via a WiMAX modem. The Customer Terminal (102) is configured with a list of available Gateways (140), should internet access not be available via the primary Gateway, the next on the list is tried in succession, until a working one is found and the connection to the internet re-established.

[072] Figure 4 illustrates the connection between the Burglar Alarm system

(470) and the Customer Terminal (480) which permits the alarm message to be transmitted whether or not the customer premises phone is in use.

[073] Generally, the Burglar Alarm system (470) is connected to the telephone network via a four-wire cable (489) to an RJ-31X connector (in the USA) or equivalent. This way the Burglar Alarm system (470) is connected in series with the in-premises phone system, which allows the Burglar Alarm system to disconnect the in-premises phone to make outgoing phone calls to report alarms irrespective of whether the in-premises telephone is in use.

[074] Relay RLl (comprising RLl A and RLl B) (471 ) is used to selectively connect the incoming phone line to the Burglar Alarm system's internal dialer (472) or to the in-premises telephone.

[075] The arrangements shown in Figures 4 and 7 allow the Customer

Terminal to monitor the connection between the Customer Terminal (480, 780) and the Burglar Alarm system (470, 770), so that an alarm can be signalled both locally and to a remote monitoring site when the connection between the Customer Terminal and the Burglar Alarm system (489, 789) is severed, interfered with or an unauthorised attempt is made to replace the primary burglar alarm panel with a secondary burglar alarm panel.

[076] Figure 6 details a possible substitution scenario in which a Secondary

Burglar Alarm Panel (606) is connected across the wired connection (614) between the Primary Alarm Panel (604) and the Customer Terminal (602). In this case the unauthorised wiring is achieved by connecting pairs 612 from the Secondary Burglar Alarm Panel (606) across pairs 608 which are used to communicate the signal between the Primary Alarm Panel (604) and the Customer Terminal (602).

[077] The invention utilises the Burglar Alarm panel' s existing ring detect circuit 474 (generally a series combination of a resistor and capacitor) to monitor the connection. Burglar alarm panels not equipped with such a circuit, can have it added during the installation of the Customer Terminal.

[078] The Customer Terminal (480) line interface comprises drivers 481 and

482 which are used to simulate the PSTN Voltages to the Burglar Alarm system. The drivers also generate a low-level signal at around 25 Hz which flows through the alarm panel's ring detector circuitry (474). Resistor 483 and amplifier 485 are used to monitor the current. The signal generated is at an amplitude that does not cause the Burglar Alarm systems ring-detector to trigger.

[079] At the service commissioning stage, the Customer Terminal's threshold detector circuit (487) is manually or automatically calibrated to match the ^' alarm panel's ring detector circuitry. During system operation, if the monitoring current varies in either direction more than a settable threshold value (for example 10%), an alarm indicating tamper is triggered unless the Burglar Alarm system is dialling or sending valid messages over its telephone line interface. For example, when the Burglar Alarm panel goes off-hook, this may affect the level of the detected signal. If the Burglar Alarm panel does not commence dialling within 10 seconds after going off-hook, an alarm is signalled.

[080] A further improvement in the monitoring of the link between the

Primary Burglar Alarm Panel and the Customer Terminal is shown in Figure 7. Figure 7 shows an embodiment in which the Phone out terminals (L3, L4) of the Primary Burglar Alarm Panel (770) are connected through a Low Pass Filter (LPF) shown as functional block 790, which is used to reject the low frequency monitoring signal described above, through an adder circuit (791) to a Voltage level detector (789). The Voltage level detector is used to monitor the return Voltage from the Primary Burglar Alarm Panel such that during normal operation, when the Primary Burglar Alarm Panel is on-hook, the Voltage level detector detects the full off-hook line Voltage produced by line drivers 781 and 782 (around -50 Volts), whereas when the Primary Burglar Alarm Panel is off-hook the Voltage level detector detects zero Volts.

[081] Should an unauthorised Secondary Burglar Alarm Panel, e.g., panel

606 in Figure 6 transition to the off-hook state, the Customer Terminal (780) detects the off-hook condition while at the same time the Voltage level detector (789) detects a non-Zero Voltage on the Phone out terminals (L3, L4). This is flagged as an illegal condition and results in an alarm condition. Thus the presence of an off-hook condition and a line voltage greater than a minimum value can be used to indicate an alarm condition.

[082] Figure 5 illustrates a communication panel arranged to enable the communication terminal 500 to be configured using a DTMF phone 518.

[083] Generally the Customer Terminal 500 is connected to a Local Area

Network (LAN) that supports the automatic configuration of the Customer Terminal's IP network settings via a Dynamic Host Configuration Protocol (DHCP) server.

[084] However, there are cases in which the Customer Terminal 500 is connected to LAN not equipped with a DHCP server so that it requires manual configuration. This requires the LAN nodes in general, and the Customer Terminal in particular to be manually configured by a network administrator, who also assigns static IP addresses to all the nodes on the local network.

[085] With reference to Figure 5, in the case that a DHCP server is not used on the LAN, the following IP network settings are required to be manually entered into the Customer Terminal for it to operate correctly on the LAN:

IP address Network mask Internet gateway address

[086] The following method enables the above IP network settings to be entered into the Customer Terminal without the use of a computer or the need for any specialised computer skills, allowing the Customer Terminal to be installed by a person who may not be computer literate:

[087] 1. The Customer Terminal 500 is re-started with its enclosure opened and a telephone handset 518 able to dial using DTMF (known as Touch Tones) plugged into the Alarm Panel interface 504 as shown in Figure 5.

[088] 2. After approximately 40 seconds, a 20 second time window is provided during which the configuration may be entered using the telephone handset.

[089] 3. During the configuration time window, when the telephone handset 518 is off-hook, the Customer Terminal indicates that it is able to accept the configuration by providing a dial-tone.

[090] 4. To commence the configuration process, the ' # ' DTMF tone is sent to the Customer Terminal from the telephone handset 518.

[091] 5. Once Customer Terminal is in configuration mode, the static IP address details and network mask are entered using the following DTMF key sequences:

* 10 * aaa * aaa * aaa * aaa # xxx * xxx * xxx * xxx # where:

aaa.aaa.aaa.aaa is the assigned static IP address xxx.xxx.xxx.xxx is the assigned network mask

[092] 6. To enter the IP address of the internet gateway into the

Customer Terminal, the following DTMF sequence is used:

* 11 * ggg * ggg * ggg * ggg # where: ggg. ggg. ggg. ggg is the IP address of the internet gateway used on the LAN

[093] For example, in order to set the Customer Terminal's IP settings to:

IP Address: 192.168.1.10

Network mask: 255.255.255.0

Default IP Gateway Address: 192.168.1.1 (others may be added in a similar manner)

[094] The operator enters the Customer Terminal's configuration mode and then enters:

*10* 192 ^' * 168 * 1 * 10 # 255 * 255 * 255 * 0 # ^♦ 11* 192 * 168 .* 1 * 1 #

[095] In each case the Customer Terminal sends two soft acceptance tones after the '#'. A series of sharp beeps informs the operator that the data has been incorrectly entered, requiring the re-entry of the full command.

[096] The operator is able to re-configure the Customer Terminal to return to

DHCP Client mode (where the IP network settings are automatically assigned by the DHCP Server on the LAN) by entering the Customer Terminal configuration mode and entering the following DTMF sequence:

* 13 * 1

[097] The Customer Terminal sends two soft acceptance tones after the ' 1 ' digit.

[098] It would be clear to one skilled in the art that the above is an example and that other data entry methods could be used to configure the Customer Terminal's IP networking parameters, including the use of voice commands by the operator to enter the data and the use of voice prompts by the Customer Terminal to assist the

operator with the data entry process. This can be extended to the operator dialling the Customer Terminal using a cell-phone and entering the configuration data using cellphone keystrokes.

[099] According to a further embodiment of the invention, a remote terminal can be adapted to communicate with a communication link via a communication device, the remote terminal including a fail-safe power supply, and the communication device can be powered via the fail safe power supply.

[0100] Figure 8 details a powering arrangement for the customer's broadband

, gateway modem (802). Broadband gateway modems (802), such as xDSL modems, cable (DOCSIS) modems and wireless (WiMAX) modems which are used to provide connectivity to the internet (801) are susceptible to local mains outages. When such an outage occurs, the modem (802) loses power and the customer's internet connection fails. This is unacceptable for critical security and telemetry applications.

[0101] The Customer Terminal (804), although powered from the main via an internal or external power supply (835), is designed to operate during mains outages, and is provided with a suitable power backup battery (825). This battery is charged and regularly tested by the Customer Terminal (804), such that remote and local notification is provided by the Customer Terminal (804) should the battery be found to be malfunctioning.

[0102] The purpose of the arrangement of Figure 8 is to ensure that the customer's internet connection continues to operate during a mains outage. This is done by implementing an auxiliary power circuit inside the Customer Terminal (804) with an adjustable output Voltage that is used to power the customer's broadband gateway modem (802). The customer's broadband gateway modem (802) is powered by the Customer Terminal (804) via power connection cable 810, whereas connection 815 is used for the bidirectional broadband data connection.

[0103] During normal operation, both the Customer Terminal (804) and the customer's broadband gateway modem (802) are powered from the mains (835). Both switch over automatically to battery (825) operation should the mains fail.

[0104] Where ever it is used, the word "comprising" is to be understood in its

"open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of. A corresponding meaning is to be

attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

[0105] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. AU of these different combinations constitute various alternative aspects of the invention.

[0106] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.