GB2322034A

GB2322034A - Telephone line monitoring arrangement

Info

Publication number: GB2322034A
Application number: GB9625399A
Authority: GB
Inventors: Brian Hamilton Edmundson
Original assignee: ROTADATA Ltd
Current assignee: ROTADATA Ltd
Priority date: 1996-12-06
Filing date: 1996-12-06
Publication date: 1998-08-12
Also published as: GB9625399D0

Abstract

A telephone line monitoring arrangement comprises a control unit (1) which periodically sends telephone calls to monitoring stations (2), each of which has a monitoring unit (3) connected between the telephone socket of the incoming line and any telephone apparatus (e.g. a handset (4)) used at that station. If the telephone line is cut, this is detected by the control station (1) and an alarm signal generated. The monitoring unit (3) includes a CLI detector circuit which intercepts calls from the control station (1) but passes other incoming calls transparently to the user.

Description

MONITORING UNIT AND ARRANGEMENT The present invention relates to a telephone line monitoring unit and to a monitoring arrangement comprising such a unit. It is often necessary or desirable to monitor telephone lines connected to burgiar alarm systems or other monitoring arrangements e.g. remote temperature sensors for supermarket refrigerators.

In one known arrangement, known as the REDCAREE system, special monitoring signals are sent from the telephone exchange to the telephone line being monitored and are used to detect interference with the telephone line.

These signals are "transparent" i.e. do not cause any telephones connected to the monitored line to ring and do not interfere with normal use of the telephone iine.

However the REDCAREE system is expensive and it would be desirable to provide an alternative in which "transparent" monitoring signals are not required.

Accordingly, in one aspect the present invention provides a telephone line monitoring unit comprising calling line identity detection means arranged to detect the line identity of an incoming telephone call, call intercepting means arranged to intercept the incoming telephone call in response to the detection of a predetermined line identity by the calling line identity detecting means and signalling means arranged to transmit a response signal in response to such interception of the incoming telephone call.

Preferably the signalling means is arranged to transmit a telephone signal (e.g.

signalling an engaged state of the telephone line being monitored) in response to such interception. However one or more other signals such as a local alarm signal and/or a radio signal can be generated additionally or alternatively to a telephone signal.

Preferably said signalling means is arranged to generate a characteristic signal indicative of the monitored telephone line being intact in response to such interception and to transmit said characteristic signal to a remote location.

Preferably the signalling means is arranged to transmit said characteristic signal to the originator of the incoming telephone call.

In a preferred embodiment the unit further comprises output means arranged to generate an external local output signal in response to such interception of the incoming telephone call, said local output signal being distinct from the signal transmitted by said signalling means.

The local output signal can for example be arranged to interrogate a sensor such as a temperature sensor in a refrigerator for example or to interrogate other apparatus e.g. alarms, detectors or other apparatus used in a security system for example. Any signals generated as a result of such interrogation could be used as local control or information signals or could be transmitted to a remote location by any suitable means.

Preferably however the unit further comprises input means arranged to receive a local input signal, the unit being arranged to transmit information contained in said local input signal the local input signal being distinct from said incoming telephone call. The local input signal could be (but is not necessarily) generated as a result of the output signal and can for example carry information about the value of a parameter sensed by a sensor (e.g. a temperature sensor) or derived from a security system.

The invention also provides a monitoring arrangement comprising a telephone line monitoring unit in accordance with the first aspect of the invention, the arrangement comprising telephone dialling means connected to a telephone line having said predetermined line identity, the telephone dialling means being arranged to generate said telephone call, the arrangement being arranged to generate an alarm signal in the absence of said response signal.

In one embodiment the arrangement is arranged to transmit said alarm signa' (preferably but not necessarily by telephone) to a station remote from the telephone dialling means. For example the telephone dialling means could be located at the premises of a security firm and the arrangement could be arranged to transmit the alarm signal to a police station and/or to the home of a key holder of the premises protected by a monitored security system.

A preferred embodiment of the invention is described below by way of example only with reference to Figures 1 and 2 of the accompanying drawing, wherein: Figure 1 is a block diagram illustrating a monitoring arrangement in accordance with the invention, and Figure 2 is a block diagram illustrating a telephone line monitoring unit in accordance with the invention and as used in the arrangement of Figure 1.

Referring to Figure 1, the arrangement comprises a control station 1 (e.g.

located at the premises of a security firm) which is provided with a conventional telephone line 10 connectable via the Public Switched Telephone Network (PSTN) 5 to any one of up to 500 monitored telephone lines 9A, 9B, 9C ... (only three are shown) of respective monitored stations (normally the premises of the security firm's clients) 2A, 2B, 2C .

At each monitored station 2A, 2B, 2C, a monitoring unit 3 is connected between the incoming telephone socket and the telephone handset 4 or other telephone equipment (e.g. a modem or facsimile machine) and is transparent to the user, in the sense that it has no effect on normal incoming or outgoing telephone calls (whether voice, fax or data).

As is described in more detail below however, when a call is received from the telephone number which identifies telephone line 10, the call is not routed to handset 4 but is intercepted. Depending on the settings of unit 3 (selectable by the user) the monitoring unit at monitoring station 2A can either: a) automatically answer the call and return a unique tone signature to control station 1 b) set itself to a "busy" state so that control station 1 will receive an "engaged" tone, or c) route the call to e.g. monitoring circuitry 7 which, in response, sends back an information carrying signal which is converted to a telephone call transmitting that information to control station 1. For example monitoring circuitry 7 could include a temperature or other sensor arranged to monitor the temperature or other parameter in local equipment and the temperature information or other information could be encoded in the telephone signal to control station 1.

The monitoring station 2B has a monitoring unit 3 which only has an input port connected to an output of a local detector 8 (e.g. a movement detector in a security system).

Hence only option a) or option b) is selectable for monitoring station 2B. The local detector 8 transmits a signal to unit 3 whenever movement is detected and unit 3 can be arranged to telephone either control station 1 or another remote station 6 (e.g. a police station) in response to such detection.

Monitoring station 2C has a control unit 3 which has no additional connections and in this case only the state of its telephone line 9C is monitored. Hence in this case option a) or option b) is selectable.

It will be apparent that the arrangement possesses considerable flexibility.

In order to enhance this flexibility, control station 1 generates the required telephone calls to monitoring stations 2A, 2B, 2C ... by means of one or more modems 18 under the control of a programmed personal computer 7. These telephone calls are made at regular intervals. Computer 7 can also be arranged to respond to various error conditions (e.g. the absence of expected "engaged" or other distinctive tone from a monitoring unit 3) by displaying an appropriate message on screen and/or generating an audible or other alarm signal.

Computer 7 can also be arranged to monitor (or even to change) the settings of the above-mentioned options a) b) or c) of the various monitoring units 3. All the above operations can be overidden or controlled from the keyboard, mouse or other input device of computer 7.

Turning now to Figure 2, each monitoring unit 3 comprises an interface module 11 having a standard connector for connection to telephone line 9 and arranged to receive and generate telephone calls. Incoming telephone calls are passed to a CLI detector 12 which detects calls from control unit 1 by comparing the telephone number of the incoming call with a list of telephone numbers in a lookup table 17.

If the telephone number of the incoming caller is not that of a control unit 1 then the call is immediately routed via a microprocessor 13 and switching unit 14 to a telephone outlet socket 15 of the unit which is connected to e.g. handset 4 or other telephone receiving apparatus.

If the telephone number is that of control unit 1 then microprocessor 13 intercepts the call and causes interface 11 either to signal an "engaged" tone or to send a characteristic tone to control unit 1 (depending on whether option a) or option b) is selected) e.g. by means of switches (not shown) coupled to inputs of the microprocessor.

Additionally, if option c) has been selected (e.g. by means of such switches) microprocesser 13 outputs a signal at port 16 of switching unit 14, which is received by an answering unit 19. Unit 19 is responsive to this signal to output a trigger signal at output port 20 which is received by monitoring circuit 7. A parameter sensed by circuit 7 (e.g. temperature) is then sampled and the resulting signal is output to port 21 of unit 19. The relevant parameter information is then telephonically encoded in unit 19 and transmitted via port 16, switch 14 and interface 11 as a telephone call to control unit 1.

It will be apparent that in a simpler form (as shown in monitoring station 2C of Figure 1) port 16, answering unit 19 and associated monitoring circuit 7 can be omitted.

Claims

A telephone line monitoring unit comprising calling line identity detection means arranged to detect the line identity of an incoming telephone call, call intercepting means arranged to intercept the incoming telephone call in response to the detection of a predetermined line identity by the calling line identity detecting means and signalling means arranged to transmit a response signal in response to such interception of the incoming telephone call.
2. A telephone line monitoring unit according to claim 1 wherein said signalling means is arranged to transmit a telephone signal in response to such interception.
3. A telephone line monitoring unit according to claim 2 wherein said telephone signalling means is arranged to signal an engaged state of the telephone line being monitored in response to such interception.
4. A telephone line monitoring unit according to claim 1 or claim 2 wherein said signalling means is arranged to generate a characteristic signal indicative of the monitored telephone line being intact in response to such interception and to transmit said characteristic signal to a remote location.
5. A telephone line monitoring unit according to claim 4 wherein said signalling means is arranged to transmit said characteristic signal to the originator of the incoming telephone call.
6. A telephone line monitoring unit according to any preceding claim, further comprising output means arranged to generate an external local output signal in response to such interception of the incoming telephone call, said local output signal being distinct from the signal transmitted by said signalling means.
7. A telephone line monitoring unit according to any preceding claim, further comprising input means arranged to receive a local input signal, the unit being arranged to transmit information contained in said local input signal, the local input signal being distinct from said incoming telephone call.
8. A monitoring arrangement comprising a telephone line monitoring unit according to claim 6 or claim 7 wherein said input means and/or output means is arranged to receive input signals from and/or to transmit output signals to local monitored apparatus.
9. A monitoring arrangement according to claim 8 wherein the local monitored apparatus comprises a security system.
10. A monitoring arrangement according to claim 8 as dependent on claim 7 wherein the local monitored apparatus comprises sensor means arranged to generate said local input signal, the local input signal conveying information about the value of a parameter sensed by the sensor means.
11. A monitoring arrangement comprising a telephone line monitoring unit according to any of claims 1 to 7 or as defined in any of claims 8 to 10, the arrangement comprising telephone dialling means connected to a telephone line having said predetermined line identity, the telephone dialling means being arranged to generate said telephone call, the arrangement being arranged to generate an alarm signal in the absence of said response signal.
12. A monitoring arrangement according to claim 11 which is arranged to transmit said alarm signal to a station remote from the telephone dialling means.
13. A monitoring arrangement substantially as described hereinabove with reference to Figures 1 and 2 of the accompanying drawing.