GB2395392A

GB2395392A - Controlling a customer telephone line

Info

Publication number: GB2395392A
Application number: GB0216307A
Authority: GB
Inventors: David Jones; Kevin Avery
Original assignee: Tunstall Group Ltd
Current assignee: Tunstall Group Ltd
Priority date: 2002-07-13
Filing date: 2002-07-13
Publication date: 2004-05-19
Anticipated expiration: 2022-07-13
Also published as: GB2395392B; GB0216307D0

Abstract

A circuit (30) is coupled between telephone equipment particularly a care monitoring system (20a), and a customer telephone line of a PSTN. The circuit senses a direction of a control signal asserted on a control line (13), and in response selectively suppresses a signal line (12). The telephone equipment (20), e.g. a care monitoring system (20a), may thereby seize control a customer telephone line, and override equipment (20b) at other extension socket outlets (15, 15b) , such as in response to an emergency alarm (21).

Description

Controlling a Customer Telephone Line The present invention relates in

general to a method and apparatus for controlling a customer telephone line.

A telecommunications network such as a PSTN (Public Switched Telephone Network) provides a telephone line to a customer's premises. Often, the customer extends the telephone line at their premises by providing a plurality 0 of extension socket outlets, thereby allowing multiple items of telephone equipment to be coupled to the telephone line. For example, several telephone handsets, a computer, a fax machine, and other items of telephone equipment are each coupled to the telephone line through 15 the extension sockets.

A problem arises in that once a first piece of telephone equipment seizes control of the telephone line, any other telephone equipment is prevented from making or 20 receiving telephone calls. This problem is particularly acute in the field of care monitoring systems used to

monitor elderly or infirm patients. It is desired to make an outgoing call from a care alarm unit to a remote care monitoring and control centre, such as in response to an 25 emergency event. If the telephone line is already in use, then such emergency call is delayed or even prevented altogether, which may have life-threatening consequences for the monitored patient.

30 An aim of the present invention is to provide a method and apparatus capable of controlling a customer telephone line. In particular, it is desired to enable priority access to a telephone line which is already in use. Also,

it is desired that the method and apparatus are simple, effective and reliable, and ideally involve minimal adaptations to an existing telephone line.

5 According to a first aspect of the invention there is provided a circuit coupleable between a telephone equipment and a telephone line having a signal line and a control line, the circuit comprising: a direction sensing unit arranged in use to sense a direction of a control lo signal asserted on the control line; and a suppression unit arranged in use to selectively suppress the signal line, responsive to the direction sensing unit.

Suitably, the direction sensing unit senses a 5 direction of current flow on the control line.

Suitably, the suppression unit comprises: a switch unit arranged to suppress the signal line; and a by-pass unit arranged to selectively bypass the switch unit.

Suitably, the switch unit is arranged to interrupt the signal line with an open circuit interruption.

A first preferred embodiment of the circuit may 25 comprise: a switch unit comprising a relay for interrupting the signal line; a by-pass unit comprising a rectifier for selectively by-passing the switch unit; and a current sensing unit comprising a rectifier for sensing current flow on the control line coming from or going 30 toward the telephone line.

A second preferred embodiment of the circuit may comprise: a switch unit comprising a relay for

interrupting the signal line; a direction sensing unit comprising a first transistor for sensing current flow on the control line coming from or going toward the telephone line; and a by-pass unit comprising second and third 5 transistors responsive to the current sensing unit for selectively by-passing the switch unit.

The circuit of the second preferred embodiment may comprise an output unit for providing a low resistance lo output path for current flow on the control line toward the telephone line.

Suitably, the circuits are adapted to be arranged in an extension socket outlet.

According to a second aspect of the present invention there is provided a telephone line control apparatus, comprising: a plurality of circuits each coupleable between a telephone equipment and a telephone line, each 20 circuit comprising a direction sensing unit arranged in use to sense a direction of a control signal asserted on a control line, and a suppression unit arranged in use to selectively suppress a signal line; and at least one control unit adapted to assert the control signal onto the 25 control line.

Suitably, the control unit is arranged to assert the control signal onto the control line through any first one of the plurality of circuits, thereby causing suppression 30 of the signal line at each other of the plurality of circuits.

According to a third aspect of the present invention there is provided a control unit adapted to assert a control signal onto a control line of a telephone line, the control signal having a detectable direction.

Suitably, the control unit is a care alarm unit. The care alarm unit is preferably arranged to generate the control signal in response to a trigger event.

lo According to a fourth aspect of the present invention there is provided a method for controlling a customer telephone line, comprising the steps of: determining a direction of a control signal asserted on a control line of the telephone line; and selectively suppressing a 5 signal line of the telephone line, in response to the detected direction.

The method may further comprise the step of determining a trigger event and, in response, asserting 20 the control signal onto the control line of the telephone line. Suitably, the trigger event comprises any one or more of: (a) detecting an alarm condition; or (b) recognising a 25 calling line identity of an incoming call on the telephone line. For a better understanding of the invention, and to show how embodiments of the same may be carried into 30 effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figure 1 is a schematic diagram of an example customer telephone line installation; Figure 2 is a schematic circuit diagram of a preferred 5 circuit for controlling a customer telephone line; and Figure 3 is a schematic circuit diagram of a second preferred circuit for controlling a customer telephone line; and Figure 4 is a schematic flow diagram of a preferred method for controlling a customer telephone line.

Figure 1 shows an example customer telephone line 15 installation, illustrating a preferred embodiment of the present invention. The telephone line 10 is linked to a telecommunications network such as a PSTN, through a master termination 14. The telephone line 10 comprises a signal line 12 to carry voice or other data, and a control 20 line 13. Conveniently, the signal line 12 comprises two or three conductors according to requirements of a country of installation. For example, in the United Kingdom the signal line comprises two conductors, while the USA has three conductors. The control line 13 may take any 25 suitable form, but preferably comprises at least one conductor separate from the signal line 12. The control line 13 ideally uses spare conductors within an existing telephone line 10. Typically, a telephone line 10 provides unused conductors in addition to two or three 30 conductors used for the signal line 12. These additional unused conductors are employed for the control line 13.

The example installation of Figure 1 comprises a plurality of extension socket outlets 15 allowing telephone equipment 20 such as telephones, fax machines, computers, and other devices, to be coupled to the 5 telephone line 10. The extension sockets 15 are installed at convenient locations around a customer premises, allowing the telephone equipment 20 to be plugged into any convenient socket 15. Any of the telephone equipment 20 may seize the telephone line by going off-hook. Other 10 telephone equipment is then prevented from making or receiving telephone calls.

As shown in Figure 1, the preferred embodiment of the present invention provides one or more circuits 30, each 15 coupled between one or more telephone equipment 20 and the telephone line 10. The circuit 30 acts to selectively disconnect the telephone equipment 20 from the signal line 12, in response to a control signal asserted on the control line 13.

Figure 2 shows one circuit 30 in more detail. The circuit 30 is coupled to the control line 13 of the telephone line 10. In this example the control line 13 comprises two conductors 13a, 13b separate from the 25 conductors of the signal line 12. In alternate embodiments one or more conductors, such as a common ground line, are shared between the control line 13 and the signal line 12.

30 The circuit 30 comprises a switch 35, and first and second rectifiers 33, 37. In this embodiment the switch 35 is a normally-closed relay, while the rectifiers 33, 37 are first and second diodes. The first diode 33 forms a

direction sensing unit 32, while the switch 35 and the second diode 37 form a suppression unit 34.

When a control signal is asserted on the control line 5 13, the relay 35 attempts to suppress the signal line 12.

As a result, access to the signal line 12 is interrupted.

Conveniently, the control signal is a DC voltage, which causes current to flow through a winding of the relay 35.

Typically, a control signal of 12 volts DC is used.

10 Optionally, a resistor 39 determines correct voltage drop across the relay 35 and limits current flow. The circuit 30 suppresses the signal lines 12 only whilst the control signal is asserted on the control line 13. Once the control signal is removed or de-asserted, the circuit 30 15 reverts to a quiescent state. Advantageously, the relay 35 provides an open-circuit interruption of the signal line 12. The relay 35 is simple, cost-effective and robust, also being relatively resistant to unexpected conditions on the signal line 12 such as a lightning strike.

The first diode 33 conducts when current flows on the control line conductor 13a in a first direction toward the telephone line 10, and does not conduct when current flows in the reverse direction. A control unit, such as a 25 telephone equipment 20, is adapted to assert the control signal on the control line 13, and is coupled to one side of the circuit 30. The telephone line, including the control line 13, is coupled to the other side of the circuit. Hence, the direction sensing unit 32 determines 30 whether the control signal has been asserted from the first side (i.e. from a control unit) or from the second side (i.e. from elsewhere on the telephone line).

The second diode 37 acts as a by-pass unit, to selectively by-pass the relay 35 in response to the control signal direction sensed by the direction sensing unit 32, i.e. the first diode 33. Hence, when the control 5 signal is asserted by the control unit on the first side of the circuit, the second diode 37 by-passes the relay 35 and the signal line 12 is not interrupted. Even though the control signal has been asserted on the control line 13, the control unit 20 that asserts the control signal lo still has access to the signal line 12.

Referring again to Figure 1, a control unit 20a is arranged to assert the control signal on the control line 13 through one of the circuits 30, in this case circuit 5 30a. The circuit 30a senses the direction of the control signal as coming from the control unit 20a and maintains access to the signal line 12. Meanwhile, each other circuit, including a second circuit Bob, senses the direction of the control signal as incoming from the 20 control line 13 and, in response, suppresses the signal line 12. Therefore, any other telephone equipment, such as a telephone handset 20b, is disconnected from the signal line 12.

25 In the preferred installation of Figure 1, the control unit 20a is a care alarm unit arranged to monitor an elderly or infirm patient. Suitably, the care alarm unit is coupled to a number of alarm sensors 21 including personal sensors such as a heart rate monitor and a fall 30 detector, and environmental sensors such as a smoke detector and a moisture detector, amongst others, as appropriate to a condition of the patient being monitored.

When one of the sensors 21 generates an alarm condition,

the alarm unit 20a asserts the control signal on the control line 13, causing any other telephone equipment 20, 20b to be disconnected. The alarm unit 20a then has exclusive access to the signal line 12 of the telephone 5 line 10 to make a priority outgoing call to alert a care monitoring centre of the alarm condition.

In a particularly preferred embodiment of the present invention the alarm unit 2Oa is adapted to recognise a lo calling line identity (CLI) of an incoming call received on the telephone line 10. In response to recognition of the incoming CLI, the alarm unit 2Oa asserts the control signal on the control line 13, thereby preventing the incoming call being answered by any other telephone 15 equipment. Advantageously, this allows an incoming call to be answered by a desired piece of telephone equipment, in this case the alarm unit 20a. Preferably, recognition of the incoming CLI and assertion of the control signal is performed relatively quickly, ideally within 200mS, before 20 a first power ring is asserted on the signal line 12.

Hence, the call is answered by the desired telephone equipment 20a without causing other telephone equipment to ring, which may disturb a user, or result in the call being answered at an unintended telephone equipment.

The circuit 30 of Figure 2 divides the control signal voltage between the relay 35 and the resistor 39. This means that in order to maintain the open circuit interruption of the signal line 12 by the relay 35, 30 current must flow through the resistor 39. Consequently, energy is dissipated in the resistor 39. This may be undesirable as in certain conditions, for example if mains power is interrupted, the energy required to assert the

control signal may be provided from a limited resource such as a battery. A battery within a single control unit 20 may be required to provide current to relays 35 located at a plurality of circuits 30. This places heavy demand 5 on such a battery and may reduce its ability to suppress the signal line 12 if used frequently or for extended periods of time.

Figure 3 illustrates a second preferred embodiment of lo the circuit 30.

In Figure 3, the circuit 30 is coupled to the control line 13 of the telephone line 10, and also comprises a direction sensing unit 32' and a suppression unit 34'. In 15 the second embodiment, the direction sensing unit 32' comprises first and second resistances R1, R2, first and second rectifiers, D1, D2 and a current sensing transistor TR1. The first and second rectifiers D1, D2 comprise an output unit of the direction sensing unit. The 20 suppression unit 34' comprises third, fourth and fifth resistances R3, R4, R5, a switch 35 comprising a normally closed relay, and second and third transistors TR2, TR3.

When a control signal is asserted on the control line 25 13 and received on one side of the circuit 30 such as from a telephone line, the relay 35 attempts to suppress the signal line 12. Conveniently, as with the first preferred embodiment shown in Figure 2, the control signal is a DC voltage, which causes current to flow through a winding of 30 the normally closed relay 35. The third transistor TR3 is turned on by a base current supplied through the fourth resistor R4. In this way, the relay 35 has the full control signal voltage across it, and current flowing in

the winding causes the signal line 12 to be open circuit interrupted. On the other hand, when a control signal is asserted 5 on the control line 13 from the other side of the circuit 30, such as from a control unit, current is caused to flow through the current sensing transistor TR1 and the second resistor R2. In addition, current also flows through the output unit D1, D2. The output unit provides a parallel 10 low resistance path through the first and second rectifiers D1, D2. Conveniently, these two semiconductor rectifiers D1, D2 are provided in the series with one another, giving sufficient voltage drop in the parallel path to avoid shorting out the base-emitter junction of 15 the current sensing transistor TR1. When the current sensing transistor TR1 turns on, it causes the second transistor TR2 to conduct, which in turn turns off the third transistor TR3. Switching off the third transistor TR3 ensures that the relay 35 is not activated.

The first resistor R1 and the fifth resistor R5 ensure that the first and second transistors TR1, TR2 respectively are maintained in the off state when no control voltage is applied to the control line 13 by the 25 control unit, and thus protect the circuit 30 from spurious operation in response to e.g. small changes in ground potential on the control lines 13.

Advantageously, the circuit 30 of Figure 3 employs a 30 relay 35 rated at the full DC control signal voltage, which reduces energy consumption in the suppression unit 34' when interruption of the signal lines 12 takes place.

This has particular benefit when the control unit is battery powered.

As can be seen from the example embodiment of Figure 5 2, the circuit 30 is small, simple and cost-effective.

The second embodiment of Figure 3 is still small and cost-

effective, and although relatively more complex it offers the advantage of low power consumption. In each case, the circuit 30 is readily adapted to be installed in an 10 extension socket 15. Preferably, the circuit 30 is manufactured integral with parts of the extension socket 15, such as a removeable faceplate. The circuit 30 is installed at a customer premises by removing existing extension sockets 15, or ideally just an existing 15 faceplate, and replacing with an adapted socket or faceplate including the circuit 30. Once installed, the circuit 30 remains in position. It is relatively difficult for a customer to circumvent the safe operation of the circuit 30. In normal use, existing telephone equipment is 20 allowed unimpeded access to the telephone line. However, a control unit 2Oa, such as a care alarm unit in an emergency situation, is able to seize control of the telephone line 10 and make a priority call.

25 The circuits 30 are each identical. Therefore, the control unit 20a is positionable at any extension socket 15. Likewise, other telephone equipment 20, 20b is readily moved to any desired extension socket. The telephone line is thereby controlled in any desired 30 configuration of the attached telephone equipment.

Figure 4 shows a preferred method for controlling a customer telephone line. In step 301, a control signal is

asserted onto a control line associated with the telephone line. Step 303 comprises detecting a direction of the control signal asserted on the control line. Step 305 comprises selectively suppressing a signal line of the 5 telephone line, in response to the detected direction.

A method and apparatus have been described for controlling a customer telephone line. Circuits are provided of simple and cost-effective construction. The lo circuits are robust and reliable. In normal use, the circuits allow unimpeded access to a signal line of a telephone line. However, when necessary, such as in response to an emergency condition, access to the signal line is interrupted at selected locations, allowing a 15 priority location to have exclusive access to the signal line. The circuits are easy to install but, once installed, are difficult to circumvent. Minimal adaptations are required to an existing telephone line installation. The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and

which are open to public inspection with this 25 specification, and the contents of all such papers and

documents are incorporated herein by reference.

All of the features disclosed in this specification

(including any accompanying claims, abstract and 30 drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification

(including any accompanying claims, abstract and drawings), may be replaced by alternative features serving 5 the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

lo The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any 5 novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A circuit coupleable between a telephone equipment and a telephone line having a signal line and a control 5 line, the circuit comprising: a direction sensing unit arranged in use to sense a direction of a control signal asserted on the control line; and a suppression unit arranged in use to selectively suppress the signal line, responsive to the direction sensing unit.

5

2. The circuit of claim 1, wherein the direction sensing unit senses a direction of current flow on the control line.

3. The circuit of claim 1 or 2, wherein the 20 suppression unit comprises: a switch unit arranged to suppress the signal line; and 25 a by-pass unit arranged to selectively by-pass the switch unit.

4. The circuit of claim 3, wherein the switch unit is arranged to interrupt the signal line with an open circuit 30 interruption.

5. The circuit of any of claims 1 to 4, comprising:

a switch unit comprising a relay for interrupting the signal line; a bypass unit comprising a rectifier for selectively 5 by-passing the switch unit; and a current sensing unit comprising a rectifier for sensing current flow on the control line coming from or going toward the telephone line.

6. The circuit of any of claims 1 to 4, comprising: a switch unit comprising a relay for interrupting the signal line; a direction sensing unit comprising a first transistor for sensing current flow on the control line coming from or going toward the telephone line; and 20 a by- pass unit comprising second and third transistors responsive to the current sensing unit for selectively by passing the switch unit.

7. The circuit of claim 6, comprising: an output unit for providing a low resistance output path for current flow on the control line toward the telephone line.

30

8. The circuit of any of claims 1 to 7, wherein the circuit is adapted to be arranged in an extension socket outlet.

9. A telephone line control apparatus, comprising: a plurality of circuits each coupleable between a telephone equipment and a telephone line, each circuit comprising a direction sensing unit arranged in use to sense a direction of a control signal asserted on a control line, and a suppression unit arranged in use to selectively suppress a signal line; and lo at least one control unit adapted to assert the control signal onto the control line.

10. The apparatus of claim 9, wherein the control unit is arranged to assert the control signal onto the control 15 line through any first one of the plurality of circuits, thereby causing suppression of the signal line at each other of the plurality of circuits.

ll. A control unit adapted to assert a control signal 20 onto a control line of a telephone line, the control signal having a detectable direction.

12. The control unit of claim 11, wherein the control unit is a care alarm unit.

13. The control unit of claim 12, wherein the care alarm unit is arranged to generate the control signal in response to a trigger event.

30

14. A method for controlling a customer telephone line, comprising the steps of:

determining a direction of a control signal asserted on a control line of the telephone line; and selectively suppressing a signal line of the telephone 5 line, in response to the detected direction.

15. The method of claim 14, comprising determining a trigger event and, in response, asserting the control signal onto the control line of the telephone line.

16. The method of claim 15, wherein the trigger event comprises any one or more of: (a) detecting an alarm condition; or (b) recognising a calling line identity of an incoming call on the telephone line.

17. An apparatus for controlling a customer telephone 20 line, substantially as hereinbefore described with reference to the Figures 1, 2 and 3 of the accompanying drawings.

18. A circuit for controlling a customer telephone 25 line, substantially as hereinbefore described with reference to Figure 2 or 3 of the accompanying drawings.

19. A control unit adapted for controlling a customer telephone line, substantially as hereinbefore described 30 with reference to Figure 1 of the accompanying drawings.

20. A method for controlling a customer telephone line, substantially as hereinbefore described with reference to the accompanying drawings.