GB2356529A

GB2356529A - Communications interface unit

Info

Publication number: GB2356529A
Application number: GB9927312A
Authority: GB
Inventors: Mark Joseph Cohen; Nicholas Archibald Safford
Original assignee: Scientific Generics Ltd
Current assignee: Scientific Generics Ltd
Priority date: 1999-11-18
Filing date: 1999-11-18
Publication date: 2001-05-23
Also published as: GB9927312D0

Abstract

An interface unit 10 is provided which allows a user of a mobile communications device, such as a mobile telephone 9, to be able to receive mobile communications via a fixed communications device, such as a fixed telephone 5a,5b or an answering machine 11. The interface unit may also connect to a land line communication system and be arranged so that the fixed communications device can receive calls either from the mobile communications device or from the land line communication system.

Description

2356529 COMMUNICATIONS INTERFACE UNIT This invention relates to a device

which forms an interface between a portable communication device, a f ixed communication system and a f ixed communications device. More particularly, but not exclusively, this invention relates to a device which may form an interface between a mobile telephone, a.telephone land-line and a fixed telephone at a user's residence.

Currently, mobile telephones are well known to provide communications for persons who move about between different locations. Such people may use their mobile telephone as a primary point of contact. To this end there are several existing services, which supplement the mobile telephone being a single point of contact, including call forwarding and personal numbers.

Call forwarding allows calls directed to a mobile telephone to be forwarded to an alternative number if the mobile telephone is unavailable for any reason. The user of the mobile telephone is responsible for specifying the alternative number, and for activating and deactivating the call forwarding service. The user of the mobile telephone generally incurs extra charges for forwarded calls.

Personal numbers allow the owner a single point of 2 contact through a single telephone number. Such numbers, when called, redirect the call to whichever number their owner has specified. For example, during business hours the user of a personal number may direct calls to a mobile telephone and in the evenings may direct calls to a residential number. The owner of a personal number is responsible for updating the personal number service with whichever number he may be contacted on. The originator of a call to a personal number is typically charged a premium and so the call is more expensive, than for example, a normal land line call. The owner of a personal number will typically be subjected to subscription charges and may also be charged for each call that is redirected.

According to one aspect, the present invention provides a communication system comprising: a mobile communications device; a fixed communications device; and an interface unit for interfacing said mobile communications device to said fixed communications device so that communications received on said mobile communications device can be received on said fixed communications device through said interface unit.

The present invention also provides an interface unit for use in such a communications system.

This interface unit provides the benefit to the user that 3 he may receive messages from the mobile communications appliance via the fixed communication device without having to use call forwarding or personal number type services. Another benefit of the interface unit is that it allows the user to establish a single point of contact in a non-mobile environment, for example, a domestic residence. A further benefit is that no additional charges or subscription charges, compared -to call forwarding or personal numbers, are paid for either by the user or by the originator of the call.

A further advantage of the interface unit is that it allows the user to receive incoming messages on the mobile communication device whilst maintaining a physical separation between the antenna of the mobile communication device and the user's head. This may reduce the risk of brain tumours or associated conditions.

In a preferred embodiment, the mobile communications device is a mobile telephone and the fixed communication device is a fixed telephone.

In a further embodiment, an interface for an answering machine is provided. This allows the recording of messages that the user is unable to answer himself. It also provides the benefit that if the user is, for example, already using the fixed telephone to answer a 4 call originating from the mobile communication system, then a call received from the local exchange can be answered by the answering machine.

In a preferred embodiment provision is made for the interface unit to recharge the mobile telephone's battery. Typically the interface unit will be configured so that 10 it can physically support the mobile telephone. This allows the combination of the interface unit and the mobile telephone to be more compact and also easier to use. 15 Preferably the apparatus has a plurality of interfaces for connection to a plurality of land lines and/or mobile telephones and a plurality of interfaces for connection to a plurality of fixed telephones and/or answering machines. This provides the advantage that several users 20 (each with their own mobile telephone) can have the benefit of a single point of contact and, if appropriate switching is provided in the interface unit, the additional benefit that these users can transfer telephone calls from one fixed telephone to another at 25 this point of contact.

In one embodiment, provision is made for the interface unit to derive its operating power from the fixed communication system. This gives the advantage that the interface unit need not be connected to a power supply.

The interface unit preferably includes means for enabling the user to make outgoing calls using the fixed telephone via the mobile telephone rather than via the fixed communication system, since at some times of the day call charges via the mobile telephone are lower than those via the fixed communication system. In such an embodiment, the interface unit may be configured to choose automatically the communication network that offers the lowest call charges at that time of day.

The interface unit also preferably includes appropriate RF shielding so that it is not susceptible to interference from the mobile telephone.

Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic illustration of a telephone system which allows a user to receive mobile telephone calls on a standard fixed telephone; Figure 2 schematically illustrates the way in which an interface unit which forms part of the system shown in Figure 1 can be configured to establish various 6 connections between the mobile telephone and the other elements of the system; Figure 3a is a block diagram illustrating the principle components of the interface unit shown in Figure 1; Figure 3b is a schematic diagram illustrating the components of a control unit forming part of the block diagram shown in Figure 3a; Figure 4a is a flow chart illustrating a first part of the control steps used to control the operation of the interface unit shown in Figure 3a; Figure 4b is a flow chart illustrating a second part of the control steps used to control the operation of the interface unit shown in Figure 3a; Figure 4c is a flow chart illustrating a third part of 20 the control steps used to control the operation of the interface unit shown in Figure 3a; Figure 4d is a flow chart illustrating a fourth part of the control steps used to control the operation of the 25 interface unit shown in Figure 3a; Figure 4e is a flow chart illustrating a fifth part of the control steps used to control the operation of the 7 interface unit shown in Figure 3a; Figure 5 is a schematic illustration of a further telephone system which allows a number of users to receive mobile telephone calls or land line telephone calls on a number of fixed telephones; Figure 6 is a block diagram of an alternative interface unit which may be used in another telephone system which allows a user to send and to receive mobile telephone calls on a fixed telephone; and Figure 7 schematically illustrates the way in which a mobile telephone may be physically connected to such an interface unit.

Figure 1 shows a telephone system 1 comprising a land line 2, telephone line connectors 4a, 4b and 4c, conventional telephones 5a, 5b, a mobile telephone lead 8, a mobile telephone 9, an interface unit 10, an answering machine 11 and a mains wall socket 12. As shown, the interface unit 10 has an interface Il for connection to the land line 2, an interface 12 for connection to the telephones 5a and 5b, an interface 13 for connection to the mobile telephone 9 via the mobile telephone lead 8, an interface 14 for connection to the answering machine 11 and an interface 15 for connection to the mains wall socket 12.

8 In operation, when an incoming land line call is received, the call is directed to both the answering machine 11 and the fixed telephones 5. If one of the fixed telephones 5 is picked up by the user in time, the answering machine will not answer the call. If a fixed telephone 5 is not picked up in time, then the answering machine 11 will answer the call and record a message.

In the event of an incoming mobile callf the call is directed to the fixed telephones 5 and the answering machine 11. If a fixed telephone 5 or the mobile telephone 9 is picked up in time, the answering machine 11 will not answer the call. If a fixed telephone 5 or the mobile telephone 9 is not picked up in time, then the answering machine will answer the call and record a message.

In the event of an incoming mobile call being received whilst a land line call is taking place, the mobile call will be routed to the answering machine 11. 1 f the mobile telephone 9 is not picked up, then after a specified number of rings, the answering machine 11 will answer the call and record a message.

In the event that an incoming land line call is received while a mobile call is taking place using one of the fixed telephones 5, then the land line call is routed to 9 the answering machine 11. The answering machine 11 will then answer the call after a specified number of rings (although the rings will not be heard on the f ixed telephones since the call is not routed to them) and record a message.

The way in which the interface unit 10 can make connections between these interfaces so that the system can operate in the above manner will now be described with reference to Figure 2.

Figure 2a shows the situation when the land line 2 is connected to one of the fixed telephones 5. This situation could arise either as a result of an incoming call on the land line 2 being answered by the user on one of the fixed telephones 5 before the answering machine 11 answers the incoming call or as a result of the user making an outgoing call from one of the fixed telephones via the land line 2.

Figure 2b shows the situation when the mobile telephone 9 is connected to one of the fixed telephones 5. This situation would arise when an incoming call on the mobile telephone 9 is answered by the user on one of the fixed telephones 5 before the answering machine 11 answers the incoming call.

Figure 2c shows the situation when an incoming call from the land line 2 is answered by the answering machine 11.

This situation might arise if the user is unable to pick up either of the f ixed telephones 5 or if the user is unable to do so before the answering machine 11 answers the call.

Figure 2d shows the situation when an incoming call on the mobile telephone 9 is answered by the answering machine 11. This situation might arise if the user is unable to pick up either of the fixed telephones 5 or if the user is unable to do so before the answering machine 11 answers the call.

Figure 2e shows the situation when the land line 2 is connected to one of the fixed telephones 5 and when the mobile telephone 9 is connected to the answering machine 11. This situation might arise when the user is occupied with a call on the land line 2 using one of the f ixed telephones 5 and then, whilst this call is in progress, the mobile telephone 9 receives a call which is then answered by the answering machine 11.

Figure 2f shows the situation when the mobile telephone 9 is connected to the one of the fixed telephones 5 and the land line 2 is connected to the answering machine 11.

This situation might arise when an incoming call on the mobile telephone 9 is answered by the user with one of the fixed telephones 5 and then, whilst this call is in progress, an incoming call from the land line 2 is received and answered by the answering machine 11.

Figure 3a shows in more detail the main components of the interface unit 10 shown in Figure 1. As shown, in this embodiment, the interface unit 10 comprises 2 relays 20a and 20b, two line sensors 20a and 20b, an audio hybrid circuit 24, a ring voltage generator 25, a control unit 26, a power supply circuit 27 and interfaces Il to 15 corresponding to those shown in Figures 1 and 2.

In this embodiment, interfaces 11, 12 and 14 are of the two wire plain old telephone system (POTS) type.

Interface 13 connects to the mobile telephone 9 via the mobile telephone lead 8. Interface 13 in this embodiment, has the following connections: AUDIO OUT from mobile telephone, AUDIO IN to the mobile telephone, RING from the mobile telephone and ANSWER to the mobile telephone. The RING signal indicates that there is an incoming call to the mobile telephone 9 to be answered.

The ANSWER signal indicates to the mobile telephone that the incoming call should be connected so that the received audio is placed on the AUDIO OUT line and that audio signals to be transmitted may be found on the AUDIO IN line.

Relays 20a and 20b are double-pole double-throw (DPDT) relays and are used to connect interfaces 12 and 14 respectively to either interface Il or the audio hybrid circuit 24 and the ring voltage generator 25. These relays are biassed and in the absence of power they connect interface 12 to interface Il and interface 14 to interface Il so that land line calls can be made and answered by the fixed telephones 5, in the normal way.

As shown, a respective line sensor is connected in series with a POTS wire between interface 12 and relay 20a and between interface 14 and relay 20b and are used to determine, respectively, the state (i.e. whether or not it is busy) of the telephone device connected to the corresponding interface 12 and 14. In particular, if one of the fixed telephones 5 is off-hook, then current will be drawn by that fixed telephone and this current will be detected by the line sensor 22a. Similarly, if the answering machine 11 is off-hook, then it will draw current down the POTS wires and line sensor 22b will detect this.

The audio hybrid circuit 24 is an interface which converts the two simplex audio signals, AUDIO OUT and AUDIO IN, to corresponding duplex POTS signals that are carried over the two wires Pl and P2 to the two relays 20a and 20b. The audio hybrid circuit 24 also supplies a line current (which is generated by the power supply circuit 27) which is used to power the fixed telephones and the answering machine 11 when they are connected to 13 the audio hybrid circuit 24. When the fixed telephones and the answering machine 11 are connected to the land line 2 and are off-hook, they are powered by a DC line current which is drawn from the land line 2. When the fixed telephones 5 and the answering machine 11 are connected to interface 13 they cannot receive line current from the land line 2 and receive it, instead, from the power supply circuit 27 via the audio hybrid circuit 24. Instead, a separate line current generator may be provided to provide suitable line currents to the fixed telephones and the answering machines at the appropriate time.

In this embodiment, the ring voltage generator 25 receives the RING line from interface 13 and is also connected to the two POTS wires (Pl and P2) that connect to the relays 20a and 20b. When an incoming mobile call is received and the RING signal from interface 13 is activated, the ring voltage generator 25 generates a ring voltage which is used to ring the fixed telephones 5 and the answering machine 11.

As shown, the control unit receives the RING signal from the interface 13 and the line sensor signals LS1 and LS2 from the line sensors 22 and generates appropriate control signals CTRL1 and CTRL2 for controlling the relays 20 and an ANSWER signal which is transmitted back to the mobile telephone 9 via interface 13. When the 14 control unit 26 receives the RING signal from interface 13, it routes the incoming mobile call to whichever, or both, of interfaces 12 and 14 are not being used (as determined by the line sensors 22a and 22b). When the control unit 26 determines that one of the fixed telephones 5 or the answering machine 11 has gone off hook to take the mobile call, the control unit 26 asserts the ANSWER line to indicate to the mobile telephone 9 that a connection to either one of the fixed telephones 5 or to the answering machine 11 has been established and that the mobile telephone 9 may complete the connection of the incoming call.

In the case of an incoming call from the land line 2 via interface Il, the control unit 26 need take no action as both interface 12 and interface 14 are connected, by default, to interface Il. It is however necessary to ensure that if either of interface 12 or interface 14 is connected to interface 13 when a land line call is received, then that connection is maintained until the mobile call has been completed.

The power supply circuit 27 provides power to all the components of the interface unit 10. In this embodiment the power supply circuit 27 receives its power from a mains voltage supply received from interface 15 and converts this to a voltage suitable for use by the components of the interface unit 10. The connections between the power supply circuit 27 and the components of the interface unit 10 have not been shown, for clarity.

A more detailed description of the operation of the interface unit 10 of this embodiment will now be given with reference to Figure 4, which is a flow chart illustrating the control steps performed by the control unit 26 of the interface unit 10. As shown, the system starts at step S105 where the control unit 26 determines, from the signal LS1 received from line sensor 22a, whether or not one of the fixed telephones 5 is off-hook.

If neither of the fixed telephones 5 is off-hook then control passes to step S110 where the control unit 26 determines, from the signal LS2 received from line sensor 22b, whether or not the answering machine 11 is off hook. If the answering machine 11 is not off-hook then control passes to step S200 shown in Figure 4b, otherwise it passes to step S300 shown in Figure 4c. If, at step S105, one of the fixed telephones 5 was off-hook, then control passes to step S115 where the control unit 26 determines whether or not the answering machine 11 is off-hook. If the answering machine 11 is not off-hook then the processing passes to step S400 shown in Figure 4d, otherwise it passes to step S500 shown in Figure 4e.

If neither the answering machine 11 nor one of the fixed telephones 5 is off-hook, then at step S200 the control unit 26 checks the RING signal to see whether or not 16 there is an incoming mobile call. (In this embodiment, the system only checks for incoming mobile calls since incoming and outgoing land line calls are automatically routed through the interface unit 10 because of the default position of the relays 20.) If there is no incoming mobile call, then control passes back to step S105. If there is an incoming mobile call then, at step S205 the control unit 26 energises the relays 20 so as to connect both interfaces 12 and 14 to interface 13 and the ring voltage generator 25 is enabled so as to apply the ring voltage to the fixed telephones 5 and to the answering machine 11 via the interfaces 12 and 14.

Control then passes to step S210 where the control unit 26 checks to see whether or not the mobile telephone 9 is still ringing. If the incoming call (which was originally detected at step S200) on the mobile telephone 9 has ended, then control passes to step S215 where the control unit 26 reconnects both the interfaces 12 and 14 back to interface Il and the ring voltage generator 25 is disabled before returning to step S105. If the incoming call from the mobile telephone 9 is still present at step S210, then control passes to step S220 where the control unit 26 determines whether or not one of the fixed telephones 5 has been taken off-hook by the user. If one has, then control passes to step S225 where the ring voltage generator 25 is disabled and where the control unit 26 applies the ANSWER signal to the mobile telephone 17 9 to indicate that the mobile telephone 9 may connect the incoming call and reconnects the answering machine 11 back to the land line 2 by de-energising relay 20b.

Control then returns to step S105.

If at step S220 the control unit 26 determines that neither of the fixed telephones 5 have been taken off hook, then control passes to step S230, where the control unit 26 determines whether or not the answering machine 11 is off-hook. If it is then control passes to step S235 where the ring voltage generator 25 is disabled and where the control unit 26 asserts the ANSWER signal to the mobile telephone 9 to indicate that the incoming call may be connected and de-energises relay 20a in order to reconnect the fixed telephones 5 back to the land line 2.

Control then returns to S105.

If, at step S230, the answering machine is not off-hook, then control returns to step S210. Thus steps S210, S220 and S230 form a continuous checking loop which checks for one of the following three conditions taking place:

(i) the incoming call on the mobile telephone 9 ceases before it is answered, (ii) the mobile telephone 9 is answered by one of the fixed telephones 5, (iii) the incoming call on mobile telephone 9 is answered by the answering machine 11.

18 If just the answering machine 11 is originally off-hook, then at step S300 the control unit 26 determines whether or not the answering machine 11 is connected to the mobile telephone 9. If it is then control passes to step S305 where the control unit 26 determines whether or not the answering machine 11 is still off-hook. If it is then control returns to step S105, otherwise control passes to step S310, where the control unit 26 de energises the relay 20b in order to reconnect the answering machine 11 back to the land line 2 before returning to step S105. Thus steps S300 and S305 check to see whether or not a call from the mobile telephone 9 to the answering machine 11 is still in progress or if it has been completed. once the call has been completed then the answering machine 11 is reconnected back to the land line 2.

If the control unit 26 determines, at step S300, that the answering machine 11 is not connected to the mobile telephone 9 (and therefore that it is connected to the land line 2), then control passes to step S315 where the control unit 26 determines whether or not there is an incoming call on the mobile telephone 9. If there is not, then control returns to step S105 since no action is necessary as the answering machine 11 is connected to the land line 2 and there is no incoming mobile call which needs to be dealt with. If at step S315 the control unit 26 determines that there is an incoming mobile call (from 19 the RING signal), then control passes to step S320 where the ring voltage generator 25 is enabled and where the control unit 26 energises the relay 20a so as to connect the fixed telephones 5 to the mobile telephone 9.

Control then passes to step S325 where the control unit 26 determines whether or not the mobile telephone 9 is still ringing. If it is not, then control passes to step S330 which disables the ring voltage generator 25 and de energises the relay 20a so as to reconnect the fixed telephones 5 back to the land line 2 before returning to step S105. If the mobile telephone 9 is still ringing at step S325 then control passes to step S335 where the control unit 26 checks to see if one of the fixed telephones 5 is off-hook. If one is, then control passes to step S340 where the ring voltage generator 25 is disabled and where the control unit 26 applies the ANSWER signal to the mobile telephone 9 to indicate that the mobile telephone 9 should connect to the incoming call, before returning to step S105. If at step S335 the control unit 26 determines that neither of the fixed telephones 5 have been taken off-hook, then control passes back to step S325.

Thus a closed loop is formed by steps S325 and S335 which is only terminated by one of the following two events:

(i) the incoming call on the mobile telephone 9 ceases before it is answered by one of the fixed telephones 5; or (ii) the incoming call on the mobile telephone 9 is answered by one of the fixed telephones 5 before the incoming mobile call ceases.

As can be seen from a comparison of Figures 4c and 4d, the control processing for the situation where one of the fixed telephones 5 is originally off-hook is the same as for the situation when just the answering machine 11 is off -hook, except that references to the answering machine 10 and to the fixed telephones are swapped. Therefore, a further description of control steps S400 to S440 will not be given. If one of the fixed telephones 5 and the answering 15 machine 11 are both originally off-hook, then at step S500 the control unit 26 determines whether or not they are both connected to the land line 2. If they are, then no action is taken and the control returns to step S105. (The situation when one of the fixed telephones 5 and the 20 answering machine 11 are both off-hook and both connected to the land line 2 is only likely to be a temporary situation as most answering machines automatically return to the off-hook condition if a telephone on the same line is picked up.) If, at step S500, the control unit 26 25 determines that the fixed telephone 5 and the answering machine 11 are not both connected to the land line 2, then control passes to step S505 where the control unit 26 determines whether or not the fixed telephone 5 is

21 connected to the mobile telephone 9. If it is then control passes to step S510 where the control unit 26 determines whether or not the fixed telephone 5 is still off-hook. If it is, then control returns to step S105, otherwise control passes to step S515 where the control unit 26 reconnects the fixed telephones 5 back to the land line 2 before returning to step S105. If, at step S505, the control unit 26 determines that the fixed telephone 5 is not connected to the mobile telephone 9, then control passes to step S520 where the control unit 26 determines whether or not the answering machine 11 is off-hook. If it is, then control returns to step S105, otherwise control passes to step S535 where the control unit 26 connects the answering machine 11 back to the land line 2 (by de-energising the relay 20b) before returning to step S105. Thus steps S510 to S525 ensure that the appropriate device (either the fixed telephone or the answering machine 11) is connected back to the land line 2, once the incoming call on the mobile telephone 9 has been terminated.

As those skilled in the art will appreciate, the above flow chart may be implemented by the control unit 26 either with hardware or with a microprocessor run in conjunction with appropriate control software. In this embodiment, the control circuit is implemented using the latches and logic illustrated in Figure 3b. As shown, the control unit 26 has three inputs: RING, LS1, LS2 and 22 three outputs: ANSWER, CTRLl and CTRL2. LS1 and LS2 are signals from line sensors 22a and 22b, respectively, and take the value of logic level one when their respective telephone device is off-hook. CTRL1 and CTRL2 are outputs which control relays 20a and 20b respectively, and take the value of logic level one to switch the corresponding relay over to its non-default position.

RING takes the value of logic level one when there is an incoming call on the mobile telephone line and the output ANSWER takes the value of logic level one to indicate that the mobile telephone 9 should complete the connection of its incoming call. A logic level one on LS1 or LS2 forces its associated output, CTRL1 or CTRL2, to remain in the same state thus preventing the relays 20a and 20b from switching state when their associated line is already off-hook.

Figure 5 shows a telephone system 40 comprising a land line 2, three fixed telephones 5a, 5b, 5c, two mobile telephone leads 8a, 8b, two mobiletelephones 9a, 9b, an answering machine 11, a mains wall socket 12, a mains adaptor 13 and an interface unit 41. In this embodiment, interface unit 41 has three additional interfaces, 16 to 18, when compared to the interface unit 10 shown in Figure 1. As shown, the interface unit 41 has an interface 16 for connection to mobile telephone 9b via mobile telephone lead 8b, interface 17 for connection to fixed telephone 5c and interface 18 for connection to the 23 answering machine 11 (interface 14 is shown connected to the fixed telephone 5b).

In this embodiment, the interface unit 41 allows users to make extension to extension calls, i.e. calls from one fixed telephone to another, in addition to allowing one land line 2 and two mobile telephones 9a, 9b to be connected. to the three fixed telephones 5a, 5b, 5c and the answering machine 11. For example, up to three simultaneous calls may be connected through the interface unit 41: an incoming call on the mobile telephone 9a could be answered by the fixed telephone 5c, a call originating from fixed telephone 5b could be placed via land line 2 and, finally, an incoming call on the mobile telephone 9b could be answered by the answering machine 11.

A preferred way of achieving the connectivity required within the interface apparatus 41 is to use a private branch exchange (PABX) (not shown). The use of a PABX would provide the additional advantage of allowing users to transfer calls between fixed telephones so that, for example, if a mobile call on mobile telephone 9a is received at fixed telephone 5a it can be transferred to another user at fixed telephone 5c. Another f eature which could be provided by a PABX is to allow incoming calls to be associated with a particular telephone. For example, incoming calls from mobile telephones 9a and 9b 24 could be arranged to attempt to connect only with fixed telephone 5a and 5b respectively and, if not successful, then the answering machine 11. Such a feature could be of particular benefit in an office environment in which, for example, it is desirable to route calls from particular mobile telephones to particular desks.

Figure 6 illustrates the form of an interface unit 81 which may be used in a telephone system which allows incoming mobile telephone calls to be received on a fixed telephone. As shown, in this embodiment, the interface unit 81 comprises interfaces 11, 12 and 13 (which have the same functions as the corresponding interfaces in interface units 10 and 51), a relay 20, a line sensor 22, an audio hybrid circuit 24, a ring voltage generator 25, a control unit 88 and a dual tone multifrequency (DTMF) decoder 65.

In this embodiment, interface unit 81 is able to power itself from the land line 2 and, as will be described below, also allows the user to make outgoing mobile calls from the fixed telephone (not shown) connected to interface 12. As shown, in this embodiment, the interface unit 81 does not have a separate interface for connection to an answering machine. If answering services are required then these may be obtained from their respective service providers such as, for example, British Telecom for the land line 2 (not shown) and Vodafone for the mobile telephone 9 (not shown).

In this embodiment, the power supply circuit 64 includes a rechargeable battery (not shown) and so power need not be drawn continuously from land line 2 but only to recharge the battery. This recharging may be done either during a land line call or at preselected times of the day (e.g. at night). The power supply circuit 64, as well as supplying power to the interface unit 81, may also supply power to the mobile telephone 9 (not shown) via interface 13 for recharging the mobile telephone's battery.

Interface unit 81 is able to detect outgoing calls made by the fixed telephone (not shown) via interface 12 and DMTF decoder 65 and may route such calls via the mobile telephone 9 connected to interface 13. This allows the user to take advantage of lower call charges which may be available, at certain times of the day or to specified numbers, via the mobile telephone 9 rather than through the interface Il and the land line 2. In particular, DTMF decoder 65 allows the control unit 88 to recognise when a number is being dialled by the user and what the number is. If the control unit 88 determines that the call tariff would be cheaper over the mobile telephone network then the control unit 88 energises relay 20 to disconnect interface 12 from interface Il. This in effect simulates an on-hook condition to the land line 2 26 which cancels the call dialled to the land line by the user. The control unit 88 then indicates to the mobile telephone 9, via interface 13, that an outgoing call from the mobile telephone 9 is to be set up and indicates what the number to be dialled is. In this embodiment, the control unit 88 uses a DIAL signal to indicate to the mobile telephone the number to be dialled and receives an ACKNOWLEDGE signal from the mobile telephone 9 to indicate that the number has been successfully dialled.

No further action need then be taken by the control unit 88 until the end of the call, since the fixed telephone will already be connected to the mobile telephone 9 due to the prior energisation of the relay 20. The end of the telephone call is then detected by the line sensor 22 when the user returns the fixed telephone to the on-hook condition and, in response, the control unit 88 de energises the relay 20, thereby re-connecting interface 12 to interface Il.

Figure 7 is a perspective view of a further telephone system which allows mobile calls to be received using f ixed telephones. As shown, the system comprises an interface unit 71, a fixed telephone 5, a mobile telephone 9, an interface adaptor 78 and interfaces I1, 12 and 13 (which have the same function as the corresponding interfaces on interface units 10 and 51).

The interface 13 is composed of two sub-interfaces, 13a and 13b. 13a is the interface between the mobile 27 telephone 9 and the interface adaptor 78 whereas 13b is the interface between the interface adaptor 78 and the interface unit 71.

As compared to the mobile telephone lead 8, the interface adaptor 78 may perform additional functions in order to interface the mobile telephone 9 to the interface unit 71. For example, some mobile telephones have a digital interface for the audio signals at their connectors 10 instead of an analogue interface. Such telephones would require the interface adaptor 78 to perform analogue to digital and digital to analogue conversions to convert the digital format to the analogue format used by the fixed telephone. Another function that could be 15 performed by the interface adaptor at 78 is that of decryption, as some mobile telephones encrypt the signals at their output connector. The interface adaptor 78 may also be used as a cradle for 20 the mobile telephone 9 so that when the mobile telephone 9 is to be used in conjunction with the interface unit 71, the mobile telephone 9 is simply clipped into the interface adaptor 78. The interface adaptor 78 therefore also performs the function of physically supporting the 25 mobile telephone 9.

The interface adaptor 78 may be modified to allow more than one mobile to be connected to the interface unit 71.

28 This could be done, for example, either by allowing several mobile telephones to be connected to the interface adaptor 78 or by allowing several interface adaptors 78 to be interconnected.

Although the telephone system 70 shows the mobile telephone 9 being physically supported by an interface adaptor 78, other arrangements are also possible. For example, the mobile telephone 9 could be directly connected to the interface unit 71 without using either a mobile telephone lead or an interface adaptor.

However, as most types of mobile telephones have different physical arrangements, a number of different variants of the interface unit will then have to be produced: one for each type of mobile telephone. A similar situation applies with regard to the electrical interface of the mobile telephones. Another alternative is to provide the interface unit with an interface 13 capable of detecting the type of mobile telephone to which it is connected, and configuring itself to suit the mobile telephone.

Various other modifications will now be described which may be made to the embodiments described above.

The land line 2 which connected the interface unit to the f ixed communications system was described above in terms of a two wire POTS telephone system. As those skilled in 29 the art will appreciate, alternatives to this arrangement are possible. one alternative is to use a radio communication link to the local exchange to form a radio "land line". Such a land line is not "mobile" since it relies on a fixed transceiver at each end of the radio communications link. This alternative has the advantage of easy deployment when the user's residence is remote from the telephone exchange. Another alternative to the conventional two wire POTS land line is a fibre-optic land line between the user and the local exchange. This alternative allows greatly increased data rates when compared to a two wire POTS land line.

The interfaces 13 and 16 (to a mobile telecommunications appliance) were described above in terms of two simplex audio signals: AUDIO OUT and AUDIO IN. As those skilled in the art will appreciate, alternatives to this interface are possible. one alternative is to use a single digital audio in/out interface, through which the digital signals are passed.

The embodiments of the interface unit were described above in terms of exemplary telephone systems which included various combinations of mobile telephones, fixed telephones, answering machines and land lines. As those skilled in the art will appreciate, the general principles of these embodiments can be applied to any mobile communication system, such as a mobile data communication system. For example, the interface unit may be used to allow a user of a mobile facsimile machine to interface with a fixed facsimile machine or the like.

The interface unit was described above deriving its operating power either from a mains wall socket 12 or from the land line 2. As those skilled in the art will appreciate, alternatives are possible... One alternative is to use batteries to power the interface unit. This alternative has the advantage that it would not require a connection, for example, to the mains supply but also has the disadvantage that the batteries would need to be periodically replaced.

In the above embodiments, an answering machine was provided and connected to the interface unit. As those skilled in the art will appreciate, the answering machine may derive its power from a connection to a mains supply or it may draw its power from the interface unit.

Additionally, the answering machine may be incorporated within the interface unit itself. Where the answering machine can detect that one of the fixed telephones has been lifted, the interface unit may be arranged to pass control of the incoming land line or mobile call to the fixed telephones in the event that one of the fixed telephones or the mobile telephone is picked up when the answering machine is answering a call.

31 The interface unit was described above connecting to a two wire POTS telephone system. As those skilled in the art will appreciate, the interface unit can be adapted to operate with any other telecommunications system. In one alternative, the interface 12 is used to form the DECT base station interface for a DECT cordless telephone.

Another alternative is to provide an infra-red communications channel to a cordless telephone. An additional alternative is to adapt one or more of the interfaces Il and 13 for connection to a digital communications channel, for example, an ISDN line. A digital communications channel has the advantage that, whilst capable of conveying suitably encoded audio signals, it could also/instead be used to convey data to, for example, a computer.

The relays 20 were described above as being biased towards interface Il. As those skilled in the art will appreciate, they could, however, be biased instead towards interface 13. In this case, however, some telecommunications regulatory authorities require that, for example, during a power cut a connection from the fixed telephones 5 to the land line 2 is maintained.

With regard to the interface apparatus 10, this requirement is that a connection is maintained between interfaces Il and 12 during any loss of power. If the relays 20 are biased towards 13 then one way of ensuring that a connection between Il and 12 is established during 32 such emergency conditions is to have a local store of power, for example, a rechargeable battery to enable the relays to be switched so as to create a path from interface 12 to Il. Such an embodiment is not preferred, however, because of the need for the additional battery.

Furthermore, although the relays 20 were described above in terms of electromechanical relays, those skilled in the art will appreciate that alternatives are possible.

one alternative is to use a combination of semiconductor switches so that, for example, interface 12 can be connected to either interface Il or interface 13.

33

Claims

CLAIMS:

1. An interface unit for interfacing a fixed communications device to a mobile communications device or to a land line communications system, the interface unit comprising:

a first interface for interfacing to the mobile communications device; a second interface for interfacing to the fixed communications device; a third interface for interfacing to the land line communications system; a switch for connecting said first interface to said second interface or for connecting said second interface to said third interface so that said fixed communications device can receive communications from either said mobile communications device or said land line communications system; and means for controlling the position of said switch.

2. An interface unit according to claim 1, further comprising:

means for receiving a signal from said mobile communications device through said first interface indicating that an incoming call is being received on said mobile communications device; means for receiving a ready signal from said fixed communications device through said second interface, 34 indicating that said fixed communications device is ready to receive said incoming mobile communication; and means for applying, upon receipt of said ready signal, an answer signal to said mobile communications device through said first interface, for causing said mobile communications device to answer said incoming communication, so that said fixed communications device can receive said incoming communication via said first and second interfaces.

3. An interface unit according to claim 1 or 2, wherein said switch comprises a relay.

4. An interface unit according to any preceding claim, wherein said interface unit comprises a line sensor for sensing a state of said fixed communications device, and wherein said control means is operable to control the position of said switch in dependence upon the sensed state of said fixed communications device.

5. An interface unit according to any preceding claim, wherein said control means comprises a latch and logic circuits.

6. An interface unit according to any of claims 1 to 4, wherein said control means comprises a microprocessor and control software.

7. An interface unit according to claim 2, wherein said control means is operable to control said switch in dependence upon said signal sent by said mobile communications device to said interface unit.

8. An interface unit according to any preceding claim, wherein said interface unit further comprises means for drawing power from said land line communications system.

9. An interface unit according to claim 8, wherein said mobile communications device comprises a battery and wherein said interface unit is operable to draw power from said land line communications system to supply to said mobile communications device for recharging said 15 battery. 10. An interface unit according to any of claims 1 to 7, wherein said interface unit comprises a power connector for receiving power from an external supply. 20 11. An interface unit according to any preceding claim, comprising means for receiving a ring signal from said mobile communications device and a ring voltage generator which is operable to generate and apply a ring voltage to 25 said fixed communications device to cause said fixed communications device to ring upon receipt of said ring signal.

36 12. An interface unit according to any preceding claim, further comprising means for detecting an identifier of a recipient for a communication originating from said fixed communications device and means for supplying said identifier to said mobile communications device so that a communication can be made from said fixed communication device on said mobile communications device through said interface unit to said recipient.

13. An interface unit according to claim 12, further comprising a DTMF decoder for decoding DTMF tones generated by said fixed communications device and control means for passing appropriate dialling signals to said mobile communications device for establishing a communications channel with said recipient.

14. An interface unit according to any preceding claim, wherein said first interface is for interfacing to a mobile telephone.

15. An interface unit according to claim 15, wherein said second interface is for interfacing to a fixed telephone.

16. An interface unit according to claim 15, wherein said second interface is for interfacing to an answering machine.

37 17. An interface unit according to any of claims 1 to 14, wherein said second interface is for interfacing to a computer.

18. An interface unit according to any preceding claim, comprising a cradle for physically supporting said mobile communications device. 19. An interface unit according to claim 18, wherein 10 said cradle is detachable from said interface unit. 20. An interface unit according to any preceding claim, further comprising circuitry for converting signals received from said mobile communications device into 15 signals which are suitable for said fixed communications device. 21. An interface unit according to claim 20, wherein said conversion circuitry is detachable from said 20 interface unit.

22. An interface unit according to claim 21 when dependent upon claim 19, wherein said conversion circuitry is located within said cradle.

23. An interface unit according to any preceding claim, comprising a plurality of first interfaces for interfacing a plurality of mobile communications devices 38 to said fixed communications device.

24. An interface unit according to claim 23, wherein the communication interface between said fixed communications device and each of the mobile communication devices is different and wherein said interface unit comprises a respective interfacing circuitry for each mobile communication device.

25. An interface unit according to any preceding claim, further comprising a plurality of second interfaces for interfacing said mobile communications device to a plurality of fixed communications devices, so that communications received on said mobile communications device can be received on any one of said fixed communications devices through said interface unit.

26. An interface unit according to claim 25, wherein said interface unit comprises switching circuitry for allowing a mobile communication which is received on a first fixed communications device to be transferred to a second fixed communications device.

27. An interface unit according to claim 25 when dependent upon claim 23, wherein said interface unit is operable to associate a respective one of said first interfaces with a respective one of said second interfaces so that an incoming mobile communication is 39 initially directed to a predetermined fixed communication device.

28. An interface unit according to any preceding claim, comprising a plurality of third interfaces for interfacing said fixed communication device to either said mobile communications device or to any one of a corresponding plurality of land line communications systems.

29. A communications system comprising:

a mobile communications device; a fixed communications device; a land line communications system; and an interface unit for interfacing said fixed communications device to either said mobile communications device or said land line communications system so that said fixed communications device can receive communications from either said mobile communications device or said land line communications system.

30. A communications system according to claim 29, wherein said interface unit comprises a switch for connecting said fixed communications device to either said mobile communications device or said land line communications system and control means for controlling the position of said switch.

31. A communications system comprising:

a mobile communications device; a fixed communications device; a land line communications system; and an interface unit according to any of claims I to 28 for interfacing said fixed communications device to either said mobile communications device or said land line communications system.

32. A communications system according to any of claims 29 to 31, wherein said mobile communications device is connected to said interface unit via an electrical connection.

33. A communications system according to any of claims 29 to 32, wherein said fixed communications device is connected to said interface unit via an electrical connection.

34. A communications system according to any of claims 29 to 33, wherein said fixed communications system is connected to said interface unit via an electrical connection.

35. A communication system according to any of claims 29 to 34, wherein said fixed communications device comprises a fixed telephone.

41 36. A communication system according to any of claims 29 to 3 4, wherein said fixed communications device comprises an answering machine.

37. A communication system according to any of claims 29 to 34, wherein said fixed communications device comprises a computer. 38. An interface unit substantially as described herein 10 with reference to or as shown in the accompanying drawings. 39. A communication system substantially as described herein with reference to or as shown in the accompanying 15 drawings.