AU660975B2 - Device and method for telephony interconnection intended to offer continuity of service to independent stations in a communications network - Google Patents

Description

A."

AUSTRALIA

60975 Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: 0 6 0 DEVICE AND METHOD FOR TELEPHONY INTERCONNECTION INTENDED TO OFFER CONTINUITY OF SERVICE TO INDEPENDENT STATIONS IN A COMMUNICATIONS NETWORK.

The following statement is a full description of this invention, including the best method of performing it known to me:- S.:6 *8S* Nt .15..6

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la Device and method for telephony interconnection intended to offer continuity of service to independent stations in a communications network.

The invention relates to telephony.

It is more particularly intended to serve in a communications network between fixed stations, such as telephone sets, and fixed terminals, the said fixed stations being linked to the telephony channels of the network while the fixed terminals comprise means forming an antenna (more simply called "antenna" in the rest of the text) for mutual interaction over distance with independent stations, such as portable telephone handsets.

Such a network is, for example, that known by the trade mark POINTEL, and the invention finds a particularly advantageous but not limiting application therein.

The POINTEL network does not permit, in its current definition, offering the user of a portable handset o continuity of service, when the latter moves, even if all eeee 20 the fixed terminals situated in the vicinity of the user :'..provide complete radio frequency coverage. In fact, it is anticipated .urrently that the telephony communication in 0oo* progress will be broken off as soon as, the user moves out of the radio frequency zone covered by the fixed terminal having initialised the radio frequency link of this telephony communication.

0 0 a S• The invention aims to provide a solution to this problem.

According to the presentation there is provided a telephony device for use in a communications network between fixed station (SF) and fixed terminals, the fixed stations being linked to telephony channels, the fixed terminals each 2 having an antenna for radio communication over one of number of radio frequency channels with independent stations the telephony device comprising: means for interfacing with the antennae of a plurality of the fixed terminals, means for connecting said fixed terminals to the telephony channels, specific means, linked to the means for interfacing and means for connecting, for establishing a telephony relationship between at least one of the independent stations (SA) and a fixed station (SF) linked to the telephony channels through a primary link between the independent station (SA) and the means for connecting, via the antenna of a primary one of the fixed terminals (BFRl), and for establishing at least one secondary link between the at least one of the independent stations (SA) and the connecting means, via the antenna of a secondary fixed terminal (BFR2) selected from among the fixed terminals using predetermined selection criteria, .Go.

20 station-analysis means (MTS), incorporated in the ,*6 .0 independent station, for generating a predetermined request information item in response to a predetermined station condition of the primary link, wherein the specific means responds to reception of the 000:.. 25 request information item, by switching the telephony relationship to pass through the secondary link, wherein the means for interfacing comprise, with respectively the ,0.0 antennae of the primary and secondary fixed terminals, C°e 'first primary and secondary interface stages for a 0 30 plurality of radio frequency channels, and wherein the specific mean.s comprise: 3 primary terminal-processing means (MPT-1 UCB-1), linked to the first primary interface stage (ET1-1) for establishing, within the primary link, a primary radio frequency link between the independent station (SA) and the antenna on at least one of the radio frequency channels of the primary fixed terminal (BFR1), for associating the primary radio frequency link one-to-one with a link identifier (LID1), and for delivering the link identifier (LID1) to a second primary interface stage (MOD-1), transfer means (URBS) linked to the second primary interface stage for receiving the link identifier (LID1) and for communicating to a second secondary interface stage (MOD-2) a link information item (INFL) containing at least the link identifier (LID1), and secondary terminal-processing means (MPT-2 UCB-2), linked to the said first and second secondary interface stages (ET1-2 MOD-2), for establishing, within the secondary link, a secondary radio frequency link between the independent station (SA) and an antenna on at least one S 20 of the radio frequency channels of the secondary fixed terminal (BFR2), using the link identifier (LTD1).

9o The specific means are then, moreover, suitable for responding to the reception of this request information item, by switching the said telephony relctionship so that it passes through this secondary link.

This secondary fixed terminal is advantageously selectable among a chosen group of terminals which are adjacent to the primary fixed terminal.

The request information item then advantageously contains S* 30 this link identifier.

The selection criteria for the secondary fixed terminal can 4 result from the analysis of at least one first characteristic deducted from the primary radio frequency signal transmitted in the course of the primary radio frequency link on at least one of the radio frequency channels of the primary fixed terminal, and from analysis of at least one second characteristic deduced from this primary radio frequency signal.

This first characteristic is, preferably, determination of the level of the said primary radio frequency signal in the primary fixed terminal while the second characteristic comprises, preferably, determination of the level of the radio frequency activity resulting from the transmission of the primary radio frequency signal, on the radio frequency channel associated *ith the secondary fixed terminal, the 15 counterpart of the radio frequency channel associated with the primary fixed tjrminal, on which the said primary radio frequency signal is transmitted.

i According to one embodiment of the invention, at least part S"of the constituent parts of the device can be incorporated 20 in at least one specific module.

it is also possible for these constituent parts to be S"incorporated within at least some of the connecting units for the fixed terminals belonging to the communications network.

The subject of the invention also provided a method of telephony interconnection, for use in a communications network between fixed stations and fixed terminals, the fixed stations being linked to telephony channels and the fixed terminals each having an antenna for radio communication over one of a number of radio frequency channels with independent stations, the method comprising the steps of: 5 connecting said fixed terminals to the telephony channels through a connecting means, establishing a telephony relationship between an independent station and a fixed station linked to the telephony channels, by a primary link between the independent station and the connecting means, via the antenna of a primary one of the fixed terminals, selecting a secondary fixed terminal on the bases of predetermined selection criteria, establishing a secondary link between the independent station and the connection means, via an antenna of the secondary fixed terminal, in response to a predetermined station condition, relating to the primary link, generating from the independent station a predetermined request information item, and in response to o 15 reception of the request information item and a link ""identifier associated with the primary link, wherein the link identifier is associated one-to-one with a primary 999999 S" radio frequency link within the primary link, switching the telephony relationship to pass through a secondary radio *g99 20 frequency link within the secondary link.

Other advantages and characteristics of the invention will appear on examining the detailed description below and the attached drawings in which: 9. 9.

Figure 1 represents a block diagram of a communications network of the POINTEL type of the prior art; Figure 2 represents a block diagram of a first configuration of a communications network equipped with means according to the invention; Figure 3 represents a block diagram of a specific module belonging to the device according to the invention; Figure 4, 5 and 6 diagrammatically illustrate other means 6 It is assumed now that the invention applies to the POINTEL network whose structure provided up to the present will now be very briefly described with reference to Figure 1.

Independent stations SA, such as portable telephone handsets, are capable of mutual interaction over distance with a radio channel with antennae ANT of fixed radio terminals BFR.

The radio frequency exchanges between the independent stations and the terminals are governed by a standard of British origin called "CAI" ("Common Air Interface"). The exchanges take place by frequency modulation making use of one frequency band per radio communication.

These fixed terminals BFR are connected to terminal connecting units URB by a specialised control channel 9 CCS. Each terminal connecting unit thus manages a group of fixed terminals BFR.

A fixed terminal can be directly connected to the telephony channels CTPU of the public switched telephone 20 networks. In this case the unit URB which manages it is not connected to these telephony channels.

A fixed terminal may not be directly connected to the telephony channels CTPU. In this case, its connection is carried out by the intermediary of its connecting unit 25 which is then directly connected to the channels CTPU.

Each fixed terminal BFR can only send out telephone calls towards the telephony channels CTPU but can certainly send out or receive radio calls destined for or originating from independent stations SA.

The communications network comprises, in addition to the telephony channels CTPU, a digital communications medium 7 CNPU, operating, in principle, by packets, such as the TRANSPAC (registered trademark) network. In the rest of the text, the expression "communications medium" will be replaced by the term "channel" for the sake of uniformity, although the person skilled in the art knows that the significance of the term "channel" may not be the same as in the case of telephony channels.

On to these digital signal channels CNPU are connected the various units URB as well as other constituent parts of the POINTEL network designated by the references CAP, CEPP and CEDP.

The POINTEL authorisation centre CAP, manages, for the whole of the POINTEL network, especially the subscriptions and thus the authorisations of the POINTEL 15 users to call a fixed station SF connected to the telephony channels CTPU, from an independent station. To this end, the terminal connecting units URB are linked to the centre CAP by the digital channels CNPU.

The connecting units URB are also linked to the main POINTEL operation centre CEPP, via the digital channels CNPU, with the aim of transfer of data relating to the telephony communications exchanged so that the centre CEPP can transmit this data to a billing system.

t The decentralised POINTEL operation centres CEDP are management installations intended to regionally supervise the operation of the network and especially to detect o* anomalies in operation of the connecting units URB and/or the fixed terminals BFR.

It should be noted that the centres CEDP can communicate, by the intermediary of the digital channels, data to the centres CEPP with the aim of national supervision.

-8- When a telephony communication is exchanged between an independent station SA and a fixed station SF, a radio frequency link is established between this independent station and the fixed terminal BFR whose radio frequency zone covered by this fixed terminal contains this independent station. Moreover, the fixed terminal can be connected to the public switched telephone network directly, or also by the intermediary of the connecting unit URB which manages it, according to the connecting configuration of the network adopted.

As already mentioned above, when the user carrying the independent station SA goes out of the zone covered by the terminal BFR having initialised the radio frequency link, the telephony communication in progress is broken off.

The POINTEL network, in its current definition, as well V, as the CAI standard, do not then permit offering this user the possibility that radio communication might be automatically relayed through a terminal other than that which initialised this communication.

The main aim of the invention is therefore to remedy this omission.

To this end, generally, there is provided: means of interface with the antennae of a plurality of fixed terminals, means of connection to the telephony channels of the network, specific means, linked to the interface and connection means, suitable 9 for establishing a telephony relationship between an independent station and another station, for example a fixed station, linked to the telephony channels of the network, by the intermediary of a primary link between the independent station and the connection means, via the antenna of a primary fixed terminal, for establishing at least one secondary link between the independent station and the said connection means, via the antenna of a secondary fixed terminal, chosen on the basis of predetermined selection criteria, and station-analysis means, incorporated in the independent station, suitable for generating a predetermined request information itemr relating to the primary link; the specific means are thus suitable for responding to the reception of the said request information item, in principle in the secondary terminal, by switching the said telephony relationship so that it passes through this secondary link.

In order to establish the various links, the interface 20 means comprise, with respectively the antennae of the primary and secondary fixed terminals, first primary and i secondary interface stages for a plurality of radio frequency channels.

It is thus arranged that the specific means comprise: primary terminal-processing means, linked to the said first primary interface stage of the primary fixed terminal, suitable for establishing, within the said primary link, in accordance with the CAI standard, a primary radio frequency link between the independent station and the antenna of this fixed terminal, on at least one of these radio frequency channels.

10 The primary terminal-processing means thus characterise, in accordance with the CAI standard, this primary radio frequency link one-to-one by a link identifier LID1. This link identifier is different from the identifier LID of the POINTEL commuunications network which has, for example, been sent out by the independent station SA when the user has wanted to be connected to the POINTEL network with the aim especially of calling another station. It will be seen later that, according to the invention, the request information item contains this link identifier LID1 and that the specific means will use it in order to reestablish telephone communication if the user goes out of the zone of radio coverage of the primary fixed terminal.

After having extracted this link identifier LID1, the primary terminal-processing means deliver it to a second primary interface stage.

The specific means also comprise transfer means, linked to this second primary interface stage, suitable for receiving this link identifier LID1 and for communicating it to a second secondary interface stage, situated at the ".site of the secondary fixed terminal. In fact, these transfer means are suitable for communicating a link 6i% information item INFL containing, in addition to this 25 link identifier, other data elements which will be e. detailed later.

Finally, secondary terminal-processing means are provided, linked to the said first and second secondary interface stages and suitable for establishing, within the secondary link, a secondary radio frequency link between the independent station and the antenna of this secondary fixed terminal on at least one of these radio frequency channels with the aid of the said link identifier LID1.

11 It will be seen later that the first and second primary intertace stages, as well as the primary terminalprocessing means are advantageously incorporated in the primary fixed terminal while the first and second secondary interface stages as well as the secondary terminal-processing means are incorporated in the secondary fixed terminal.

In the same way, the transfer means are preferably incorporated in the said connecting unit or units managing the primary and secondary fixed terminals.

It is possible, as will be seen later, for the primary fixed terminal to be connected to a primary connecting unit while the secondary fixed terminal is connected to a separate secondary connecting unit. In this case the 15 transfer means comprise, within the primary connecting unit, primary digital interface means linked to the digital channels of the network and, within the secondary connecting unit, secondary digital interface means linked to these same digital channels. The transfer means then transmit the said link information item INFL containing the link identifier LID1, between the primary and secondary connecting units, by the intermediary of the digital channels and the primary and secondary digital interface means.

25 The primary radio frequency link comprises transmission of a primary radio frequency signal on at least one of the radio frequency channels.

The said station condition, in response to which the station-analysis means will send out the request information item (link identifier LID1), thus relates to at least one of the characteristics of this primary radio frequency signal.

12 In accordance with the CAI standard, the primary radio frequency signal comprises a telephony channel and a signalling channel. The telephony message, supported by the primary radio frequency signal, comprises a specific signalling part (handshake) transported by the signalling channel, as well as a part, called useful, transported by the telephony channel. The specific signalling part makes it possible to check the state of the radio link.

It is then provided that the station-analysis means analyse the presence of this specific part and carry out radio frequency transmission of the link identifier LID1 (request information item) in the absence of this specific part. This absence may result from exiting from the zone of radio coverage of the terminal or even poor radio frequency transmission quality leading to an incomprehensible specific part on the part o. the :"independent station.

In addition to the means already quoted, the specific means comprise first analysis means of at least one first characteristic deduced from this primary radio frequency signal.

This first characteristic can then consist in determination of the level of the ,aid primary radio frequency signal at the site of the first primary stage oe 25 of the primary fixed terminal.

oe •It is also provided that the specific means comprise .9e.e.

second analysis means suitable for analysing, at the site of the said first secondary stage, at least one second characteristic deduced from the primary radio frequency signal. The cri\:eria of selection of the secondary fixed terminal can then result from analyses of the first and second analysis means.

13 The second characteristic is, advantageously, determination of the level of the radio frequency activity on the radio frequency channel of the said first secondary stage, the counterpart of the radio frequency channel of the first primary stage on which the said primary radio frequency signal is transmitted. This radio frequency activity then results from the transmission of this primary radio frequency signal.

In other words, the secondary terminal or other terminals can perceive radio frequency activity during transmission of the primary radio frequency signal between the independent station and the primary fixed terminal.

The selection criteria for the secondary fixed terminal can also comprise, in a variant, reception of the request 15 information item in this terminal.

It will be seen later that it is possible that the .o transfer means will communicate the said link information item INFL to the secondary fixed terminal, or to a.l the terminals of the group chosen from terminals adjacent to the primary fixed terminal among which the secondary S" terminal is selectable, before reception of the said request information item.

It is also possible, in a variant, that these transfer means will communicate the link information item INFL to 000 S 25 the secondary fixed terminal after reception of the request information item.

As far as the connection to the telephony channels of the network is concerned, it is provided that the connecting means comprise: a first interfaces block linked to the telephony channels of the network, 14 a second interfaces block linked to some at least of the fixed terminals of the network, and interconnection means between these interfaces.

The specific means thus comprise specific processing means linked to these interfaces blocks as well as to the interconnection means.

These specific processing means are then suitable for: establishing: 1) a telephony-station link between a first interface of the first interfaces block and the said other station, in principle the fixed telephone set, 2) a primary telephony link between a first interface 0* of the second interfaces block and a third primary interface stage of the primary fixed terminal, and 15 3) a secondary telephony link between a second interface of the second interfaces block and a third secondary interface stage of the secondary fixed terminal,

S.

establishing the said telephony relationship by 20 authorising interconnection between the first interface of the first block and the first interface of the second .block, then for authorising interconnection between the said first 5 interface of the first block and the second interface of the secoid block in order to switch the said telephony relationship.

Having now set out the main characteristics of a general nature of the device according to the invention, reference will now be made to Figures 2 to 6 in order to illustrate a first configuration of the communications 15 network in which at least one specific module UTP is provided, incorporating at least the first and second interfaces blocks, the interconnection means and the specific processing means.

It is provided that the device will comprise a plurality of specific models assigned respectively to separate attachment sectors. Figure 2 illustrates, for the sake of simplification, a single specific module UTP assigned to an attachment sector.

It will be assumed here that the primary fixed terminal possesses the reference BFR1 while three fixed terminals adjacent to the terminal BFR1 respectively possess the references BFR2, BFR3 and BFR4. The secondary fixed terminal which will be chosen is assumed here to be the 15 terminal BFR2.

It is also assumed that in this configuration the fixed terminals of the network are directly connected to the telephony channels CTPU and that a primary connecting unit URB1 manages the fixed terminal BFR1 and BFR3 via the respective specialised links CCS1 and CCS3 while a secondary terminal connecting unit URB2 manages the fixed terminals BFR2 and BFR4 via respective specialised links CCS2 and CCS4.

The first and second interfaces blocks, connected to the 25 telephony channels CTPU of the network, comprise a plurality of digitising cards for the telephony signals, *bearing the reference as MIC4, MIC11. These cards are, for example, those marketed by the French company AETA under reference ES0290.

The interconnection means are here represented by two digital linking buses BMIC3 and BMIC4 between the various cards MICj.

16 Each bus BMICj has a capacity of two megabits per second.

A card SIGM analyses the telephone numbers received from the telephony channels CTPU at the start of communication. The person skilled in the art knows how to produce such a card, for example using decoders (of telephone numbers coded according to the CCITT Q-23 standard) such as those marketed by the British company PLESSEY under reference MV8870DP.

A digital interfaces block JONM is also provided, linked to the digital channels CNPU. This interfaces block here comprises, for example, a card such as that marketed by the company MOTOROLA under reference MVME333. It is thus possible to produce a digital interface conforming to the international standard CCITT 15 The specific processing means UCM are linked to the block JONM, to the card SIGM and to the cards MICj by a linking bus BUCM. Physically, the latter can be produced by the card marketed by the MOTOROLA company under reference MVME 117A, based on the MOTOROLA 68010 processor incorporating the software part of these processing means, with which a dynamic random access memory of 2 megabytes is associated.

s*e Each bus BMICj is suitable for transporting digital data formed into a frame subdivided into a plurality of time intervals, typically 32, referenced ITO...IT31. The first time interval ITO and the seventeenth time interval IT16 are signalling intervals while the other time intervals are used for the various telephony channels.

While the signalling interval ITO is used for the purposes of synchronisation, the signalling interval IT16 is used to attribute a telephone line relating to a call entering or leaving the module UTP.

17 Thus, the specific processing means are suitable for acting on this s-.gnalling interval IT16 in order to permit reception or transmission of a telephone call in or from the first and second interface blocks MICj.

The module UTP finally comprises supply means ALSM and ALCM capable of providing voltages of 5 volts from the voltage of 48 volts delivered by the switched telephone network CTPU.

Figure 4 diagrammatically illustrates the block diagram of a terminal connecting unit URB-i. The suffix i will be assigned the value 1 when the primary connecting unit URB1 is concerned, and the value 2 when the secondary connecting unit URB2 is concerned.

The terminal connecting unit URB-i comprises a signalling S 15 unit URBS-i and a switching unit URBC-i as well as power supply means for these two units, not shown here, for reasons of simplification.

The signalling unit URBS-i here incorporates transfer means while the switching unit URBC-i is not used in this 20 variant and will be described in more detail later.

.E":a The transfer means comprise digital interface means JONo i linked to the digital channels of the network as well as to the switching unit URBC-i, and which can be produced in a manner similar to the digital interfaces block JONM of the module UTP.

These transfer means also comprise a plurality of interface cards CMB1-i...CMB4-i producing a signalling interface with the fixed terminals BFR. These cards CMBi can be, for example, those produced from cards marketed by the United States company FORCE COMPUTER INC. under reference SYS68K/ISIO-1/IA, associated with traditional modems.

18 With these various digital interfaces is associated a signalling processing unit UCS-i linked to the cards JON-i and CMB-i by a linking bus BUCS-i. The signalling processing unit is produced, for example in a way similar to the specific processing means UCM, based on the MOTOROLA processor 68010 which incorporates the software part of the transfer means.

Figures 5 and 6 illustrate a block diagram of the composition of a fixed terminal BFR-i.

The structures of the fixed terminals BFR of the network are similar. Also, the various constituent parts of this fixed terminal have references allocated the suffix j.

This suffix j takes the value 1 when a so-called "primary" element is concerned, that is to say associated 15 with the primary fixed terminal, and the value 2 when a so-called "secondary" element is concerned, allocated to the secondary terminal.

In the rest of the text, the adjectives primary and secondary may sometimes be suppressed and understood, for 20 reasons of simplification.

P The primary and secondary fixed terminals BFR1 and BFR2 respectively incorporate the primary and secondary terminal-processing means, the first primary and secondary interface stages ET1-1 and ET1-2, the second primary and secondary interfaces stages MOD-1 and MOD-2 Sas well as the third primary and secondary interfaces stages IRC-1 and IRC-2.

The fixed terminal BFR-j comprises a power supply block ALIM-j delivering the voltages plus and minus 5 volts from an input voltage of 220 volts AC. A terminalprocessing unit UCB-j is also provided, which can be produced in any way similar to the signalling processing unit.

19 The second interface stage MOD-j is, for example, produced from a card similar to that used for the cards CMB-j. This card makes possible the signalling link interface with the corresponding terminal connecting unit URB-j.

A radio frequency module RF-j is linked to a third interface stage IRC-j as well as to the terminalprocessing unit UCB-j and to the antenna ANT-j of the terminal BFR-j.

The card IRC-j comprises a module for digital interface with the module RF-j, followed by a digital/analog and analog/digital converter block produced, for example, on the basis of components such as those marketed by the company SGS-THOMSON under reference ETC 5067. This 15 converter block is itself followed by a model for analog subscriber line interface with the channels CTPU in accordance with the specifications for connection to the switched telephone network.

Finally, a link bus BUC-j makes it possible to link the 20 various components of this network together.

As illustrated in Figure 6, the module RF-j comprises a frequency changer stage FT-j linked to the antenna ANTj, followed by a signal demodulation circuit DMD-j then by a signal decoder circuit DCD-j.

25 This decoder DCD-j is suitable for discriminating on the one hand the signalling signals communicated by a link SIGN-j to a processing block MPT-j, and word signals communicated by another link PAR-j to a block PHO-j forming the interface with the card IRC-j.

The processing block MPT-j is linked to the terminalprocessing unit UCB-j as well as to a synthesiser SYN-j connected, moreover, to the frequency changer stage FT-j 20 for selection of the radio frequency channel on which the radio frequency link is established.

Such a module RF-j is, for example, that currently available from the Applicant under reference DTRF GPT- FT equipment.

It can be considered, functionally, that the first interface stage ET1-j encompasses the two frequency changer stages, the demodulation and decoding circuits for the signals as well as the synthesiser.

The terminal-processing means as well as the first and second analysis means comprise software modules incorporated within the blocks UCB-j and MPT-j.

We will now consider the case of a telephony communication established from the independent station SA with the 15 fixed station SF.

When the user is connected to the POINTEL network, by using the keypad of his handset, the station-analysis means communicate, for the attention of the fixed terminal BFR1, which here will be assumed to be the 20 primary fixed terminal, the identifier LID of the POINTEL network, as well as the identifier PID of the portable handset. The telephone call coming from the portable handset SA can be taken into account by the fixed terminal BFR1 since the primary terminal-processing means of 25 the latter already know the identifier LID of the POINTEL network. The telephone number of the called station, also composed on the keypad of the handset, as well as the identifier PID of this portable handset are transmitted by the intermediary of the primary connecting unit URB1 and digital channels of the network to the POINTEL authorisation centre CAP for checking.

21 When this checking is carried out, the transfer means of the primary connecting unit URBI establish a digital link with the specific module UTP by the intermediary of the digital channels of the network. This digital link has the aim of requesting from the specific processing means of the module UTP a call number of this specific module UTP by the intermediary of the switched telephone network CTPU. This telephony call number is referenced ABPQMCDU.

This call number ABPQMCDU is associated one-to-one with the identifier PID of the independent station and is communicated to the connecting unit URB1, returning via the digital channels of the network.

The transfer means of the unit URB1 then communicate via the signalling line of the specialised link CCSl the call 15 number ABPQMCDU as well as the authorisation from the POINTEL authorisation centre CAP, to the primary terminal-processing means of the terminal BFR1.

The primary radio frequency link is thus maintained between the portable handset SA and this fixed terminal 20 and is characterised as quoted above by the link identifier LID1, associated one-to-one with this link, and differing from the network identifier LID.

The primary terminal-processing means then communicate to the connecting unit URBI this link identifier LID1.

The transfer means of this connecting unit then broad- .cast, by the intermediary of these digital channels of the network and the specialised links to all the terminals BFR2, BFR3, BFR4 adjacent to the terminal BFR1, the link identifier INFL, containing the identifier LID1, as well as the call number ABPQMCDU of the specific module and the identifier of the independent handset PID.

Let us now return to the establishment of the primary link between the terminal BFR1 and the fixed station SF.

22 The primary terminal-processing means call the specific module UTP by the intermediary of the switched telephone network CTPU, with the aid of the call number ABPQMCDU.

In fact, only the MCDU part of this call number is analysed and used by the module UTP.

This "half-call" from the fixed terminal BFR1 to the specific module is received in the first interface of the second interfaces block of this module and will contribute to the establishment of the said primary telephony link.

The specific processing means of the module UTP then allocate, by the intermediary of the bus BMIC-j, the first interface of the first interfaces block so as to reserve a telephony line for the second "half-call" from the specific module UTP to the station SF, which will contribute to the establishment of the said telephonyt oo station link.

When this allocation is carried out, the switched telephone network sends, by the intermediary of the specific 20 processing means of the module UTP, a call tone to the primary terminal-processing means of the terminal BFR1, "I and bring about interconnection between the first interfaces of the first and second interfaces blocks of the connection means.

25 The primary terminal-processing means then dial the ooooo telephone number of the called station SF which will have the consequence of putting the station SA in communication with this station SF.

In the course of the telephony communication, when, for example, the user moves and exits the zone of radio coverage of the terminal BFR1, or else if there is any radio interference, the station-processing means of the handset will detect the lowering in level of the primary 23 radio frequency signal, especially when the latter no longer receives the specific part of the telephony message (thus the said predetermined station condition is present here).

In this case, the station-processing means will broadcast, on the various radio channels, the request information item, that is to say the link identifier LID1.

All the fixed terminals BFR2, BFR3 and BFR4, adjacent to the terminal BFR1, are able to recognise the link identifier LID1 since their respective terminalprocessing means have had foreknowledge of it.

It will be assumed, now that the user has pproached terminal BFR2, that it is this latter terminal which receives the identifier LID1 and which is therefore chosen among the group of adjacent terminals to be the secondary fixed terminal.

On reception of this link identifier LID1, the secondary terminal-processing means of the secondary fixed terminal are suitable for sending a secondary call signal to the said second interface of the second block, with the aid of the call number ABPQMCDU of the specific module, which will contribute to the establishment of the said secondary telephony link. In practice, only the part MCDU of this call number is transmitted by the switched telephone network CTPU to the module UTP.

On reception of this secondary call signal at the second interface of the second interfaces block of the specific module UTP, the specific processing means cause the interconnection between the first interface of the first interfaces block and this second interface. The telephony relationship between the independent station SA and the fixed station SF is thus switched and the user is offered 24 continuity of service.

In order to prevent untimely switching between two primary terminals, and in order to possibly leave time for the primary fixed terminal BFRl to pick up an interrupted radio frequency link again, especially in the case where an independent handset finds itself equidistant from two fixed terminals, it is preferable for the secondary terminal-processing means of the secondary fixed terminal JBFR2 only to transmit the said secondary call signal after a predetermined time delay typically of the order of 3 seconds, starting on first reception of the said link identifier LID1 at the said first secondary stage of this secondary fixed terminal BFR2. It will be recalled, in fact, that. the station- 15 processing means are able to send out the link identifier at regular intervals until the latter is received by one of the fixed terminals.

0* 0 C 0c*o We will now consider the case where the fixed station SF wishes to establish telephony communication with the independent station SA.

*o In order that the independent handset SA can be called, at no matter what geographical location, it is appropri- 0* ate that it can be located with respect to a chosen fixed *e terminal. This location information is stored in means 25 forming a data base BDP associated with each specific e" module UTP and contained, for example, in the 2 megabytes dynamic-random-access memory of the MOTOROLA 68010 processor. This data base BDP comprises, in addition to the location information of the chosen fixed terminal, here terminal BFRI, and therefore of the independent station SA, the correspondence between the call number of this handset SA and its physical identifier PID.

This location information results from a locating dialogue between the independent handset SA and the 25 chosen terminal BFR1.

The Applicant currently prefers to contemplate the principle of voluntary location on behalf of a subscriber wishing to receive telephone calls on his independent handset. It is assumed that this is the case here for the user carrying this independent station SA. This wish is recorded in the database BDP associated with the module UTP. It is also possible to associate with this wish a maximum duration during which the subscriber effectively wishes to receive telephone calls. A callable independent station will thus be equipped with means suitable for signifying refusal or acceptance to receive telephone calls. Such an autonomous station can thus effectively display its intention to receive calls.

S. 15 The locating dialogue can then in this case be the sending of a locating signal by this handset from the independent station SA to the chosen fixed terminal BFR1.

This can also be a telephony communication (incoming or outgoing) between this handset and this chosen terminal.

20 In practice, the database BDP stores, corresponding with the call number of the independent handset, the digital 0 identification (for example the address), on the digital channels, of the connecting unit of terminals URBI having carried out the last location on the basis of a location S 25 signal sent out by the handset, as well as a designation, for example the number, of the chosen fixed terminal BFRI @*see:chdtabae D "where this last location took place. Each data base BDP (here associated with a module UTP) possesses an address making it possible to contact it on the digital channels

CNPU

Inr, response to a telephone call request from a calling fixed station SF on the switched telephone network CTPU, the specific processing means of the module UTP will establish a control link with the chosen fixed terminal.

26 This control link comprises, after consultation of the corresponding data base BDP, a digital link between the module UTP and the terminal connecting unit URBI whose address corresponds to the location information item.

More precisely, establishment of this control link comprises sending a digital signal from the specific module UTP to the chosen terminal BFR1 by the intermediary of its connecting unit URBI. This digital signal comprises, in addition to identification of the terminal BFR1, an instruction for a radio call by this terminal BFR1 to the independent station SA, as well as the telephone number ABPQMCDU for a call by this terminal BFR1 to the specific module UTP.

This telephone call from the terminal BFR1 to the 15 specific processing means of the module UTP is subject to the satisfaction of additional predetermined conditions.

A first additional predetermined condition can be checking the effective capacity of the fixed terminal BFR1 to interact with the handset. This checking can include, for example, monitoring the correct operation of this terminal or even its capacity to reach the independent handset SA by radio waves.

Another additional predetermined condition may also be checking the effective presence of the subscriber ready 25 to accept the telephone call.

Moreover, the telephony-station link has been established between the fixed station SF and the first interface of the first interfaces block of the module UTP.

When the terminal BFR1 has called the module UTP for establishment of the said primary telephony link, this call being received at the first interface of the second interfaces block, the specific processing means cause interconnection of these two interfaces in order to 27 establish the telephony relationship.

As before, in parallel with this establishment, the transfer means communicate to the terminals BFR2, BFR3 and BFR4 adjacent to the terminal BFR1 the link identifier LID1 as well as the call number ABPQMCDU of the module UTP so that this telephony relationship can possibly be switched by passing through a terminal adjacent to the terminal BFR1.

It is appropriate also to note that, when the interconnection is effectively set up within the specific module UTP, the primary and possibly secondary telephony links between the independent station and the specific module are recorded as being charged to the subscriber holding the independent handset in order to bill him as 15 a consequence. The telephony-station link established between the fixed station and the module UTP is recorded as being charged to the fixed station with a view to billing it.

In the case of a telephone call coming from the indepen- 20 dent station to the fixed station all the telephony links e'e* established are charged to the caller.

We will refer now to Figure 7 which illustrates a second configuration of the network in which specific modules UTP are not provided. In contrast, the first and second t* t 25 interfaces blocks, the interconnection means and the specific processing means are incorporated into at least some of the connecting units of the network, in practice into all the connecting units. The other means of the device according to the invention remain, in this variant, installed as described above.

We also assume here that the fixed terminals are not directly connected to the telephony channels of the network CTPU but by the intermediary of their respective 28 connecting unit.

For the sake of simplicity in the description it will also be assumed here that the primary and secondary fixed terminals BFR1 and BFR2 are both connected by respective specialised links CCS1 and CCS2 to the connecting unit URB1.

If we return now to Figure 4, it will be noted that the switching unit URBC-j of the connecting unit URB-j (here URB1) comprises, in addition to the plurality of cards MIC-j, MIC-2 for digitising the telephony signals, forming the first interfaces block, a plurality of specialised acoustic interfaces cards IAP1...IAP4 suitable for being connected to the primary and secondary fixed terminals via the specialised links CCS1 and CCS2.

S 15 These cards IAPj comprise an interface with linking buses 486' BMIC5 and BMIC6, followed by a converter block similar to that used in the card IRC-j, followed in turn by a telephony interface (limited to the acoustic part) on a specialised link with the terminals.

20 The first interfaces block also comprises a plurality of cards ILA1, ILA2 suitable for producing an interface for connecting to telephony channels CTPR of a private communications network.

00 These cards exhibit a structure similar to the cards IAPj, the telephony interface over a specialised link being replaced by an analog subscriber line interface with the channels CTPR in accordance with the specifications for connection to the switched telephone network.

All of these cards are linked together by linking buses and BMIC6 as well as to a switching processing unit UCC-j linked to the signalling processing unit UCS-j.

29 This switching processing unit is, for example, produced with the aid of the MVME 117A card (already quoted), incorporating one of the software parts of the specific processing means.

When, in the case of a telephony communication established from the independent station SA to the fixed station SF, the user dials the telephone number of this fixed station, on the keypad of his handset SA, the checking procedure is carried out in liaison with the centre CAP, in a similar way to that described above.

When authorization is granted by the centre CAP, the primary radio frequency link is maintained between the portable handset SA and the fixed terminal and is characterised in a way similar to that quoted above by the link 15 identifier LID1.

S" The specific processing means of the connecting unit URBI then allocate, by the intermediary of the buses BM1C, the first interface of the first interfaces block so as to reserve a telephone line for the half-call from the connecting unit to the station SF, so as to contribute to the establishment of the said telephony-station link.

In parallel, the specific processing means allocate, by the intermediary of the cards IAP-j, the first interface :of the second interfaces block contributing to the establishment of the primary telephony link.

When these allocations are carried out, the specific processing means transmit, by the intermediary of a card CMB-j and of the signalling path of the specialised link CCS1, a call tone sent out by the channels CTPU, to the primary terminal-processing means of the terminal EFR1, and cause interconnection between the first interfaces of the first and second interfaces blocks.

30 The primary terminal-processing means then dial the telephone number of the called station SF, which will have the consequence of putting the station SA in communication with the station SF.

In the course of the telephony communication, the first and second analysis means, here formed by software modules incorporated within the terminal connecting unit URBI, analyse respectively the level of the primary radio frequency signal exchanged between the independent set and the first interface stage of the primary terminal BFR1, and the level of the radio frequency activity, resulting from the transmission of the primary radio frequency signal, on the radio frequency channels of the *'**.neighbouring terminals, the counterparts of the radio frequency channel of the first primary stage on which the said primary radio frequency signal is transmitted.

soot.: S"Needless to say that assumes that at least one of the neighbouring terminals is not saturated, that is to say that all its radio channels are not already used for 20 other radio frequency links with other independent stations.

When the level of the primary radio signal crosses a predetermined theshold, for example becomes less than -80 dBm, and when, in parallel, the level of the radio 25 frequency activity, on one of the neighbouring terminals becomes greater than another predetermined threshold, for example of the order of -60 dBm, this terminal (assumed to be the terminal BFR2) will be selected in order to switch the telephony relationship in progress.

In order to do that, the transfer means will then communicate to this terminal BFR2 the link identifier LID1.

The specific processing means will then allocate, by the intermediary of a card IAP-j, an acoustic link between this terminal BFR2 and the terminal connecting unit.

31 On reception of the link identifier LID1 sent out by the independent station, a channel will be selected on which the secondary radio frequency link will be established, and the specific processing means will break off the acoustic link between the first interface of the second interfaces block (at the site of a card IAP-j) and the primary terminal BFR1, then will carry out interconnection between the second interface of this second interfaces block and the first interfaces of the first interfaces block produced at the fixed station SF.

In order to avoid the terminal BFR1 taking up the radio link again (since it also receives the identifier LID1 sent out by the portable handset) so as to immediately generate a new switch to terminal BFR2, it can be 15 provided for a signal to be sent to a terminal BFR1 forbidding it to recognise the identifier LID1. Thus, only terminai BFR2 will be able to pick up the radio link.

For the user, switching this telephony relationship is 20 perceived as reestablishment of the radio link. It will also be noted that the outgoing path is, on the contrary, t not changed. There is thus no break in the telephonystation link to the fixed station SF.

0 It has been assumed here that the link identifier LID1 25 was communicated to the secondary fixed terminal after 0* the analysis carried out by the first and second analysis means. It could also be envisaged that, in parallel with the establishment of the primary link passing through the primary fixed terminal, the terminal connecting unit is already broadcasting the link identifier LID1 to the other neighbouring terminals, that is to say before choosing a secondary fixed terminal.

The invention also permits ensuring continuity of service, not only when the user moves, but also when the 32 external environment disturbs the radio link with the terminal, by choosina another less "disturbed" terminal, and to do this on the initiative of the independent station.

The invention is not limited to the embodiments described above but embraces all the variants contained in the scope of the claims below, especially the following: the two embodiments described, based on specific modules and without specific modules, are not incompatible. In this context a network configuration could be enviisaged in which some geographical sectors might be equipped with specific modules and other geographical sections would contain the specific means incorporated in the terminal connector units; 15 the specific module UTP, or even a connecting unit, could equally be connected to a private communications network also containing private telephony channels and private digital channels; it is also not excluded that the use could be 20 envisaged, in the second variant described, of the type of predetermined conditions and/or selection criteria used in the first variant, and conversely; *o it is also possible to include, within the module UTP or a connecting unit, a card making it possible to send out recorded standby messages to the calling users. This card could be equipped with voice synthesis generators associated with memories.

Telephone calls originating from a calling independent station to a callable independent station could certainly be envisaged. In this case, one of the fixed terminals interacting with one of the independent calling or called stations plays the role of the fixed station SF described 33 above.

More generally, an independent station is not limited to a telephony handset but relates to any object capable of interacting with a fixed terminal.

Needless to say, some of the means described above can be omitted in the variants where they have no function.

0

Claims (33)

1. A telephony device for use in a communications network between fixed station (SF) and fixed terminals, the fixed stations being linked to telephony channels, the fixed terlinals each having an antenna for radio communication over one of number of radio frequency channels with independent stations the telephony device comprising: means for interfacing with the antennae of a plurality of the fixed terminals, means for connecting said fixed terminals to the telephony channels, specific means, linked to the means for inteifacing and means for connecting, for establishing a telephony relationship between at least one of the independent stations (SA) and a fixed station (SF) linked to the telephony channels through a primary link between the independent station (SA) and the means for connecting, via the antenna of a primary one of the fixed terminals (BFRI), and for establishing at least one secondary link between the at least one of the independent stations (SA) and the connecting means, via the antenna of a secondary fixed terminal (BFR2) selected from among the fixed terminals g* using predetermined selection criteria, 25 station-analysis means (MTS), incorporated in the independent station, for generating a predetermined request information item in response to a predetermined station condition of the primary link, So 0 wherein the specific means responds to reception of the request information item, by switching the telephony relationship to pass through the secondary link, wherein the means for interfacing comprise, with respectively the 35 antennae of the primary and secondary fixed terminals, first primary and secondary interface stages for a plurality of radio frequency channels; and wherein the specific means comprise: primary terminal-processing means (MPT-1 UCB-1), linked to the first primary interface stage (ET1-1) for establishing, within the primary link, a primary radio frequency link between the independent station (SA) and the antenna on at least one of the radio frequency channels of the primary fixed terminal (BFR1), for associating the primary radio frequency link one-to-one with a link identifier (LID1), and for delivering the link identifier (LID1) to a second primary interface stage (MOD-1), transfer means (URBS) linked to the second primary interface stage for receiving the link identifier (LID1) and for communicating to a second secondary interface stage (MOD-2) a link information item (INFL) containing at least the link identifier (LID1), and secondary terminal-processing means (MPT-2 UCB-2), linked to the said first and second secondary interface stages (ET1-2 MOD-2), for establishing, within the secondary link, a secondary radio frequency link between the independent station (SA) and an antenna on at least one Sof the radio frequency channels of the secondary fixed 25 terminal (BFR2), using the link identifier (LTD1).

2. Device according to claim 1, characterised in that the secondary fixed terminal (BFR2) is selectable among a chosen group of terminals which are adjacent (BFR2, BFR3, BFR4) to the primary fixed terminal (BFR1). 30

3. Device according to claim 1, characterised in that the said request information item contains the link 36 identifier (LID1).

4. Device according to claim 1, wherein the first and second primary interface stages (ET1-1 MOD-1), as well as the primary terminal-processing means (MPT-1 UCB- 1) are incorporated into the primary fixed terminal, and the first and second secondary interface stages (ET1-2 MOD-2), as well as the secondary terminal-processing means (MPT-2 UCB-2) are incorporated into the secondary terminal.

5. Device according to claim 1, intended to serve in a communications network comprising connecting units for fixed terminals linked, on the one hand respectively to groups of the fixed terminals, and on the other hand together, wherein, the primary and secondary fixed terminals being linked to at least one (URBI) or two (URB1 URB2) of the connecting units, the transfer means (URBS) being incorporated into the said connecting unit or units.

6. Device according to claim 5, wherein the network comprises a digital communications medium (CNPU), wherein the primary fixed terminal (BFR1) is linked to a primary connecting unit (URB1) and the secondary fixed terminal (BFR2) is linked to a secondary connecting unit (URB2), wherein the transfer means (URBS) comprise, within the primary connecting unit, primary digital interface means S 25 (JON-1) linked to the digital communications medium of the network, and, within the secondary connecting unit, secondary digital interface means (JON-2) linked to the digital communications medium of the network, O* wherein the transfer means (URBS) transmit the link information item (INFL), between the primary and secondary connecting units, through the digital communications medium and the primary and secondary digital interface means. 37

7. Device according to claim 1, characterised in that the transfer means (URBS) communicate the said link information item (INFL) to the said secondary fixed terminal (BFR2) before reception of the said predetermined condition.

8. Device according to claim 7, characterised in that the transfer means (URBS) communicate the said link information item (INFL) to all the terminals of the said group before reception of the said predetermined request information item.

9. Device according to claim 1, characterised in that the transfer means (URBS) communicate the said link information item (INFL) to the said secondary fixed terminal (BFR2) after reception of the said predetermined request information item.

Device according to claim 1, wherein the interface means comprise a first primary interface stage (ET1-1) with the antenna of the plurality fixed terminal (BFR1) for a plurality of radio frequency channels, wherein the primary rAdio frequency link comprises transmission of a primary radio frequency signal on at least one of the radio frequency channels, and the said predetermined station condition relates to at least one of the characteristics of the primary radio frequency signal.

11. Device according to claim 10, characterised in that the station-analysis means (MTS), incorporated in the independent station are suitable for analysing the presence of a specific part of the telephony message 30 transported by the primary radio frequency signal, and for effecting radio frequency transmission of said request 38 information item (LDI1) in the absence of this specific part.

12. Device according to one of the preceding claims, characterised in that the selection criteria for the said secondary fixed terminal comprise reception at this terminal of the said request information item (LID1).

13. Device according to claim 1, wherein the interface means comprises, with respectively the antennae of the primary and secondary fixed terminals, first primary (ET1-1) and secondary ET1-2) interface stages for a plurality of radio frequency channels, wherein the primary radio frequency link comprises transmission of a primary radio frequency signal on at least one of radio frequency channels, wherein the specific means further comprises: first analysis means (MPT-1 CAN-1 DCD-1) including a primary processing block and a primary signal decoder for analyzing, at the level of the first primary stage, at least one first characteristic deduced from the primary 20 radio frequency signal, and second analysis means (MPT-2 CAN-2 DCD-2) including :a secondary processing block and a secondary signal decoder for analyzing, at the level of the first secondary stage, at least one second characteristic deducted from the 25 primary radio frequency signal, C S and the selection criteria for the secondary fixed terminal (BFR2) resulting from the analyses.

:14. Device according to claim 13, characterised in that the first characteristic comprises determination of 39 the level of the said primary radio frequency signal while the second characteristic comprises determination of the level of radio frequency activity, resulting from the transmission of the primary radio frequency signal, on the radio frequency channel of the said first secondary stage, counterpart of the radio frequency channel of the first primary stage on which the said primary radio frequency signal is transmitted.

Device according to claim 1, wherein at least the primary and secondary fixed terminals comprise respectively third primary (IRC-1 MOD-1) and secondary (IRC-2 MOD-2) interface stages linked respectively to the primary and secondary terminal-processing means, wherein the connecting means comprise: a first interfaces block (MICi) linked to the telephony channels, a second interfaces block linked (MICj lAPj) to at least of the fixed terminals, interconnection means (BMICj) between the first and :0 second interfaces blocks, 0 wherein the specific means comprise specific processing means (UCM BUC-M) linked to the interface blocks as well as to the interconnection means, .the specific means establishing a telephony station 25 link between a first interface of the first interfaces block and the another of the stations, a primary telephony link between a third primary interface stage (IRC-1) of the primary terminal and a first interface of the second a: interfaces block, and a secondary telephony link between a 30 third secondary interface stage (IRC-2) of the secondary 40 terminal and a second interface of the second interfaces block, establishing the telephony relationship by authorizing an interconnection between the first interface of the first interfaces block and the first interface of the second interfaces block, and authorizing an interconnection between the first interface of the first interfaces block and the second interface of the second interfaces block in order to switch the telephony relationship.

16. Device according to claim 15, wherein, while the telephony relationship from the independent station (SA) to the another of the stations is established: establishment of the primary telephony link results from a primary call signal from the third primary interface stage (IRC-1) of the primary terminal to the second interfaces block, the specific processing means allocating, in response to the primary call signal, the first interface to the first interfaces block, carrying out interconnection between the first interface of the first interfaces block and the first interface of the second block and transmitting a dialling authorization signal to the primary fixed terminal (BFR1) so that the primary fixed terminal composes the telephone number of the another of the stations.

17. Device according to claim 16, characterised in that the third primary (IRC-1) and secondary (IRC-2) interface stages are linked to the telephony channels of the network while the second interfaces block is connected a to the telephony channels of the network. 30

18. Device according to one of claims 15 to 17, characterised in that the secondary terminal-processing 41 means, incorporated in the secondary fixed terminal (BFR2), are suitable for sending a secondary call signal in the said second interface of the said second block, after reception of the said link identifier (LID1) in the said first secondary stage.

19. Device according to claim 18, characterised in that, as the station-analysis means transmit at least once the said link identifier (LID1), the primary terminal- processing means are suitable for sending the said secondary call signal after a predetermined time interval starting on first reception of the said link identifier (LID1) in the said first secondary stage.

Device according to claim 13 and one of claim 16 to 18 taken in combination, characterised in that in the presence of a primary radio frequency signal exceeding a predetermined primary threshold, and in the presence of a level of radio frequency activity exceeding a predetermined secondary threshold, the specific processing means are suitable for transmitting to the secondary terminal- processing means (MPT-2 UCB-2) a control information item in order to permit establishment of the said secondary radio frequency link.

21. Device according to one of claims 15 to 2 characterised in that it comprises a specific module (UTP) 25 incorporating at least the first and second interfaces blocks, the interconnection means and the specific processing means. o

"22. Device according to claim 1, comprising a digital communications medium, specific module (UTP) comprising a 30 digital interfaces block linked to the digital communications medi. S SS Se and the transfer means (URBS) communicating the link 42 information item (INFL) to the module through the digital communications medium.

23. Device according to claim 21 or 22, characterised in that the said link information item (INFL) comprises, in addition to the said link identifier (LIDI), a station identifier suitable for the independent station (SA) as well as a telephone call number of the specific module (UTP) suitable for being received in the said first interfaces block of this specific module (UTP).

24. Device according to claim 23 taken in combination with one of claims 18 and 19, characterised in that the secondary terminal-processing means of the secondary fixed terminal (BFR2) send the said secondary call signal with the said of a least a part of the said call number.

25. Device -ccording to claim 21, characterised in that the specific processing means are suitable for responding to a telephone call request from the another of the stations to the independent station the call request being received in the first interface of the first interfaces block by seeking to establish, in addition to the telephony-station link, the said primary telephony lying between the third primary interface stage (ETI-1) of the primary fixed terminal (BFR1) and the first interface of the second interfaces block, on the basis of 25 predetermined supplementary conditions, and on the basis of an information item for localization of the said primary fixed terminal (BFR1). e

'26. Device according to one of claims 21 to characterised in that the first and second interfaces block 30 comprise a plurality of cards (MICj) for digitisation of the telephony signals, linked by at least one link bus (BMIC3, BMIC4) forming the interconnection means, 0 43 in that the said link bus is suitable for transporting digital data using a frame subdivided into a plurality of time intervals (ITO, IT31) comprising useable intervals and signalling intervals (ITO IT16), and in that the specific processing means are suitable for acting on at least one of the signalling intervals (IT16) in order to permit reception or transmission of a telephone call in or from the first and second interface blocks.

27. Device according to one of claims 15 to 20, taken in combination with claim 6, characterised in that the first and second interface blocks, the interconnection means and the specific processing means are incorporated in at least some of the connecting units of the network.

28. Device according to claim 27, characterised in that the second interfaces block comprises a plurality of specialised acoustic interfaces cards suitable for being connected to the primary and secondary fixed terminals by a specialised link, and in that the first interfaces block comprises a plurality of cards (MICi) for digitising the telephony signals, linked together and to the acoustic interface cards by a least one link bus (BMIC2, BMIC4) forming the 0 Se interconnection means. 0 e.e..

29. Device according to any one of the preceding claims, characterised in that the communications network is a private network.

30. Device according to one of claims 1 to 28, offa$* characterised in that the communications network is a public network. 055O 0

31. A method of telephony interconnection, for use in 44 a communications network between fixed stations and fixed terminals, the fixed stations being linked to telephony channels and the fixed terminals each having an antenna for radio comunication over one of a number of radio frequency channels with independent stations, the method comprising the steps of: connecting said fixed terminals to the telephony channels through a connecting means, establishing a telephony relationship between an independent station and a fixed station linked to the telephony channels, by a primary link between the independent station and the connecting means, via the antenna of a primary one of the fixed terminals, selecting a secondary fixed terminal on the bases of predetermined selection criteria, establishing a secondary link between the independent station and the connection means, via an antenna of the secondary fixed terminal, in response to a predetermined station conditicn, relating to the primary link, generating from the independent station 20 predetermined request information item, and in response to reception of the request information item and a link identifier associated with the primary link, wherein the link identifier is associated one-to-one S* S. with a primary radio frequency link within the primary link, switching the telephony relationship to pass through a secondary radio frequency link within the secondary link.

32. A telephony device substantially as herein described with reference to the accompanying drawings.

33. A method of telephony interconnection substantially as herein described with reference to the accompanying drawings. Abstract Device and method for telephony interconnection intended to offer continuity of service to independent stations in a communications network. In a communications network between fixed stations and fixed terminals, the said fixed stations being linked to the telephony channels while the fixed terminals comprise an antenna for mutual interaction over distance with independent stations, means of connection to the telephony channels of the network are provided, and there is established a telephony relationship between an independent station (SA) and another station (SF) linked **to the telephony channels of the network, by the intermediary of a primary link between the independent 15 station (SA) and the connection means, via the antennas of a primary fixed terminal (BFR1). A secondary fixed terminal (BFR2) is chosen on the basis of predetermined selection criteria, and a secondary link is established between the independent station (SA) and the said S. 20 connection means, via the antenna of the said secondary fixed terminal (BFR2). In response to a predetermined station condition, relating to the said primary link, a predetermined request information item is generated from se- the independent station and, in response to reception of the said request information item, the said relationship as. is switched so that it passes through this secondary link. (Figure 2)