GB2304493A

GB2304493A - ISDN connection

Info

Publication number: GB2304493A
Application number: GB9617472A
Authority: GB
Inventors: Sigram Schindler; Karsten Luedtke; Frank Paetsch; Andreas Illg
Original assignee: TELES TELEMATIC SERVICES GmbH
Current assignee: TELES TELEMATIC SERVICES GmbH
Priority date: 1995-08-21
Filing date: 1996-08-20
Publication date: 1997-03-19
Anticipated expiration: 2016-08-20
Also published as: FR2738092A1; GB9617472D0; GB2304493B; FR2738092B1; DE19531948C1

Description

- 1 2304493 Method for transfer of information between terminal equipment

devices of an ISDN telecommunications connection

Description

The invention relates to a method for the transf er of information between two or more standard-conf orming terminal equipment devices of the same ISDN telecommunications connection according to the preamble of claim 1 and to an ISDN telecommunications connection f or carrying out this method.

An ISDN telecommunications system consists of terminal systems between which information is transferred standardized through transfer devices. one terminal system thereby communicates with a local bulletin board. Access to the local network of the bulletin board is through a network termination (NT).

The ISDN basic connection provides on the subscriber line (house connection) the SO interface which is located between the network termination NT and the terminal system. Frequently a subscriber connection is used at the same time for several terminal systems such as eg telephone, personal computer and telefax. The individual terminal equipment devices are arranged in a bus configuration and are connected by an S. Bus to a standard interface S..

In addition to the main function of an ISDN telecommunications system, of providing a communication between two terminal equipment devices of different telecommunications connections, it is also frequently required to provide a communication between two terminal SP1 791. P3 19 August 1996 equipment devices of the same telecommunications connection. This is not possible in the European Standard Euro-ISDN.

An example here is that one computer dials another communications subscriber and after making the connection the connection is automatically transferred to the telephone. Since a corresponding service element "equipment exchange" or "service exchange" of the ISDN connection is not provided in the European standard Euro- ISDN it is not possible to change automatically from one terminal equipment device to another terminal equipment device or where required to another service during an existing connection. In fact this is only possible in the Euro-ISDN by repeatedly operating function buttons on the terminal equipment devices involved.

In order to solve this and other problems caused by a missing communication between the terminal equipment devices it is known to provide a data line between two or more terminal equipment devices to connect these directly with each other. Through these lines it is then possible to provide communication and data transfer directly between the terminal equipment devices by by-passing the So-bus. The known solution has the disadvantage that an expensive additional interlinking of the individual terminal equipment devices is required. Also there is often the problem that corresponding interfaces do not exist on the terminal equipment devices.

A method according to the preamble of claim 1 is known from DE 39 17 169 Cl. This specification describes a method for the direct connection of terminal equipment devices connected to digital communications bulletin equipment.

SP1791.P3 19 August 1996 17- Through a channel control it is possible to produce a connection of two terminal equipment devices connected to the same S. bus wherein only one useful data channel is occupied.

The method described in DE 39 17 169 Cl allows a direct line-conveyed connection between two terminal equipment devices of a ISDN telecommunications connection. The drawback with this method is that with the existence of an internal connection one of the two useful data channels is automatically occupied. Also to carry out the known method an independent channel control is required whereby additional apparatus expense and additional costs are incurred.

Based on this prior art the object of the present invention is to provide a method for the transfer of information between two or more terminal equipment devices of the same ISDN telecommunications connection as well as a corresponding ISDN telecommunications connection wherein a transfer of information between the terminal equipment devices is carried out in a simple way without occupying the useful data channels.

This is achieved according to the invention by a method with the features of claim 1 and by an ISDN telecommunications connection with the features of claim 9.

The method according to the invention allows a transfer of information between the terminal equipment devices of a telecommunications connection solely on the signalling channel so that the existing B-useful data channels are readily available. An internal code is used for the SP1 791. P3 19 August 1996 transfer of information between the terminal equipment devices and as the modules are used the protocol-conf orming signalling commands def ined in the ISDN which the terminal equipment devices send to the bulletin board or network termination. These signalling commands are certainly used for another purpose and for the transfer of information are not used in their actual meaning but as code. A transfer of information through a direct line- conveyed or packageconveyed connection between the terminal equipment devices does not therefore take place.

The invention adopts the fact that a transfer of information between the terminal equipment devices does not require a direct connection through a basic channel. The information to be transferred frequently only represents short references or commands from one terminal equipment device to the other. By way of example the information to be transferred exists in the command to automatically pick up a connection already existing on the B-channel. The fact that according to the invention a transfer of information only takes place on the signalling channel does not thereby rule out that the transferred information is used to build up or break down the connection on one or both of the basic channels. The transfer of information is to be separated from the measures and commands released by the transferred information.

The solution according to the invention uses the protocol or standardconforming behaviour of the bulletin board and/or network termination to the signalling commands of the terminal equipment devices serving as code. Utilizing standard- conforming behaviour means that reactions of the bulletin board or network termination to certain signals of sp l 791 P3 19 August 1996 1-7.. 1 the terminal equipment devices def ined according to the telecommunications standard used, and thus accompanying procedures and protocols of the data protection level and/or bulletin level are recognized by the terminal equipment 5 devices and used to send data.

The standard conformity of the individual terminal equipment devices thereby remains. More particularly no functions are exercised by the terminal equipment devices which are not provided according to the relevant standard. Through the transfer of information between the terminal equipment devices according to the invention it is now possible f or functions which were previously carried out manually to now be carried out automatically.

With the solution according to the invention there are no additional costs since the bulletin board or network termination only reacts according to standard.

In a preferred embodiment of the invention a terminal equipment device sends as signalling commands ISDN standard data elements or parts thereof to the bulletin board and/or network termination. These react to the ISDN standard data elements or their parts in a standard-conf orming way.

Through a certain time sequence when sending the standard data elements and/or the type of standard data elements or parts thereof information is coded for another terminal equipment device and a transfer of data is possible in this way. The ISDN standard data elements relate in particular to data packages of the OSI level 2.

In another preferred embodiment standard data elements or parts thereof sent on the transmission line of the SP1791.P3 19 August 1996 signalling channel from a f irst terminal equipment device are reflected in a standard-conforming way to the receiving line and read by a second terminal equipment device wherein the standard data elements in addition to their own function inside the ISDN additionally code information and thus represent data to be transferred. A ref lection of the transmitted data is hereby carried out without additional functions having to be implemented in the bulletin board or in the network termination.

It is preferred to use the standard-conforming behaviour of the bulletin board or network termination when calling a terminal endpoint identifier (TEI). For a clear determination of the terminal equipment device identity in the ISDN a procedure is defined for allocating an address wherein the terminal endpoint identifier (TEI) is part of the protocol data element. A TEI allocation procedure is carried out in particular by an automatic TEI allocation wherein the management authority of the terminal equipment device asks for a TEI at the bulletin board.

In an advantageous design a first terminal equipment device in order to ask for a terminal endpoint identifier sends a data package (ID request) to the bulletin board, wherein the data package (ID request) has an identification number R, produced by the terminal equipment device and this identification number Ri codes data. To this end a corresponding code unit is provided in the terminal equipment device. The identification number R, is then 30 reflected in a standard-conforming way from the bulletin board unchanged to the receiving line of the signalling channel and read by a second terminal equipment device and recognized as data information. A transfer of data takes SP1791.P3 19 August 1996 place in this way between the terminal equipment devices.

In a further advantageous design a code is produced by a terminal equipment device, which causes a signalling between terminal equipment devices. This may happen through a request for a TEI which is unusual but tolerated by the system, or possibly through an otherwise unnecessary multiple request for a TEI. For this the other terminal equipment devices need only overhear the answer of the bulletin board to the repeated TEI inquiry and recognize it as code. Alternatively the other terminal equipment device overhears the content of the echo D-channel on which the Dchannel content stemming from the terminal equipment devices is slipped backed to the terminal equipment devices. The multiple TEI inquiry serves as a trigger to release services on the part of the other terminal equipment devices.

A specific code is thereby advantageously provided for each terminal equipment device. By way of example a triple request f or a TEI signals a PC, a f ourf old request f or a TEI signals a telefax.

An automatic change of apparatus and where applicable service from a first terminal equipment device to a second 25 terminal equipment device during an existing connection is preferably carried out by using a standard PARK function of the ISDN. The f irst terminal equipment device thereby produces at f irst a code through repeated calling up of a terminal endpoint identifier (TEI). Then the first terminal 30 equipment device after producing this code interrupts the current transaction according to a standard SUSPend function whereby the transaction number (CALL REFERENCE) is released without the corresponding connection being terminated. The SP1791 P3 19 August 1996 second terminal equipment device recognizes the code produced by the first terminal equipment device as a signal and picks up automatically, ie without human intervention, the transaction interrupted by the first terminal equipment device through a standard RESume function. An equipment exchange takes place which can also be accompanied with a change of service, possibly from telephone to telefax.

With the automatic exchange of apparatus and possibly 10 service there is also a transfer of information between the terminal equipment devices without violating the standard conformity of the terminal equipment devices. SUSPend and RESume functions are provided according to standard. The transfer of information however allows an automated action of these functions which hitherto had been carried out manually eg by pressing buttons.

Further advantageous and preferred embodinents of the invention are characterised in the sub-claims.

Figure 3 The invention will now be described below in detail with reference to various embodiments shown in the figures in the drawings in which:

Figure 1 shows an ISDN subscriber connection with several terminal equipment devices; Figure 2 shows the physical and logical connection between two terminal equipment devices according to the prior art; shows the physical and logical connection between two terminal equipment devices according to the invention; Figure 4 shows the command sequence with a change of SP1791 P3 19 August 1996 77 equipment according to the invention; and Figure 5 shows diagrammatically the reflection of an ID request data package with coded identification number R, at a bulletin board for information transfer.

According to Figure 1 several terminal equipment devices TE1, TE2, TE3 (TE = Terminal Equipment device) are connected to a network termination NT of an ISDN basic connection.

The terminal equipment devices TE1, TE2, TE3 can be for example a telephone TE1, a personal computer TE2 and a telefax TE3. It is also possible to have terminal equipment devices of a similar kind. The terminal equipment devices TE1, TE2, TE3 are arranged in a bus configuration on a S. bus 2.

The network termination is connected by a connection line 1 to a bulletin board V which manages the transfer channels of the network. The network termination NT is divided (not shown) in known way into two functional units NT1, NT2 wherein the functional unit NT1 produces the coupling with the connecting line 1 and the functional unit NT2 allows the common use of a network connection through the terminal equipment devices TE1, TE2, TE3.

At the standardized reference point S a physical, standardized interface 50 is formed to which the terminal equipment devices TE1, TE2, TE3 are linked through the S. bus. At the interf ace two pairs of cores are used per transfer direction. All part signals, thus the signals of the D channel and the B channels are combined in the time multiplex.

SP1791 P3 19 August 1996 I- For communication between the terminal equipment devices TE1, TE2, TE3 and the network when using services, a user signalling is produced whose protocols are structured according to the OSI reference model (OSI Open Systems Interconnection). Then a difference is made between a bit transfer level (level 1), a security level (level 2) and a communicating level (level 3). Signalling then takes place solely on the-D-channel.

The protocol LAPD (link access procedure on D-channel) belongs to level 2 and undertakes the task of securing all information being transferred in the D-channel against transfer errors and ensures the allocation of clear terminal endpoint identifiers TEI. Each terminal endpoint TE1, TE2, TE3 operated on the bus configuration must have a different terminal endpoint identifier TEI so that the bulletin board V of the network can recognize on receiving a signal which terminal endpoint was the sender, and can send information accurately to a specific terminal equipment device. For TEI allocation the. terminal equipment device sends a data package (IDrequest) in which it asks for a TEI from the bulletin board V. This package is answered by the bulletin board with an IlID-Assignedll or with an IlID-Deniedll.

Figure 2 shows the physical (solid line) and logical (dotted) line connection between two terminal 'equipment devices TE1, TE2 with network termination NT and bulletin board V according to the Euro-ISDN standard. The terminal equipment devices TE1, TE2 are connected physically with the network termination NT and bulletin board V through the S, bus 2. A transfer of information between the terminal equipment devices TE1, TE2 is not possible. Accordingly there is also no logical connection between the terminal SP1791.P3 19 AuguSt 1996 __II 1 equipment devices TE1, TE2 but only a logical connection between each one terminal equipment device and the bulletin board V.

Applications which require a transfer of information between the terminal equipment devices, such as an automatic exchange of equipment, are therefore not possible. Thus it is not possible with a computer TEI to dial a subscriber and after making the connection to transfer the connection 10 automatically to the telephone TE2.

Figure 3 shows the physical and logical connection of two terminal equipment devices TE1, TE2 with the network termination NT and the bulletin board V according to the invention. Here a transfer of information between the terminal equipment devices is possible. The possibility thereby exists of a non-standardized communication between two or more terminal equipment devices.

A first method according to the invention for signalling between terminal equipment devices will now be explained with reference to Figure 4 where an automatic change of equipment is carried out from one terminal equipment device TE2 (personal computer) to another terminal equipment device TE1 (telephone) The task is for the terminal equipment device TE2 (personal computer) to call up a connection and after making this connection to transfer this automatically to the terminal equipment device TE1 (Telephone).

To the network according to Figure 4 is connected on the right the bulletin board and the terminal equipment device of the dialled subscriber (not shown).

SP1791.P3 19 August 1996 After the input of the command to make a connection at the PC (TE2) this transfers the target address or a part of the target address as well as compatibility data to the bulletin board V in the message SETUP. As receipt the protocol data element CALL PROCEEDING is sent from the bulletin board.

Also a free B-channel is allotted to the calling terminal equipment device. As soon as the connection wish of the target exchange becomes known it selects the addressed connection, checks the compatibility and sends the connection wish to all terminal equipment devices of the called subscriber.

If a terminal equipment device of the dialled subscriber is in a position to take the call, the call is indicated to the dialled subscriber (ringing tone). The network then sends the protocol data element ALERT to the subscriber being called. The protocol data element CONNECT is sent when the connection is established (receiver is lifted). A receipt CONNECT AKNowledge is then provided at the terminal equipment device which has established the connection.

For an automatic transfer of the completed connection from the PC to the telephone of the subscriber being called, the PC first requests repeatedly (three times) within a predetermined time a TEI from the bulletin board. The multiple request for a TEI within a predetermined tiTae represents a code. A request of this kind produces a standard conforming behaviour of the bulletin board V, namely an allocation of a TEI to the personal computer. The bulletin board V does not recognize or is not interested that the PC already has a TEI per se.

After a triple request for a TEI the PC triggers a PARK SP1791.P3 19 AugUSt 1996 7- function. The PARK function is provided as standard in the Euro-ISDN and allows the parking of a connection for exchanging the terminal system or rerouting on the bus.

A preferably preset identification number (CALL IDENTITY) is thereby allocated by the terminal equipment device for the parking process (eg number 7). The identif ication number (CALL IDENTITY) identifies and serves as the code word for the parked connection.

In the protocol of level 3 the parking is introduced by the terminal system (here: PC) through a SUSPend. The Bchannel remains reserved in the bulletin board and the transaction number (CALL REFERENCE) is released. Through a protocol data element SUSP ACKnowledge SUSP is acknowledged and a timer is started. If the time which is set to 2 minutes runs out before the parking is lifted then the connection is broken. In the case of a dialled subscriber the parking is indicated by a protocol data element STAT.

The telephone overhears the repeated request for a TEI through the PC. This can happen in two ways. In one variation the telephone simply overhears on the receiving line of the base connection the standardconforming reaction 25 of the bulletin board, ie the allocation of TEIs. The other variation uses the fact that the network termination NT according to standard slips the D-channel contents stemming from the terminal equipment devices in its own echo Dchannel to the terminal equipment devices. For overhearing, 30 the terminal equipment devices, in this case the telephone, evaluate the echo-D channel. So that the sof tware can recognize a code in this variation an additional HDLC controller or similar module is required to ensure access to SP1791 P3 19 August 1996 1 - the echo D channel. In order to evaluate the code a corresponding evaluation or decoding unit is provided in both cases in the telephone.

The evaluation unit is formed as a programmable ROM (PROM) which overhears the signals of the other terminal equipment devices, recognizes certain non-standardized codes and releases a corresponding reaction of the terminal equipment device. Presently the PROM recognizes the multiple request of the PC for a TEI or the multiple allocation of a TEI through the bulletin board as a code for the telephone. Through the multiple allocation of a TEI through the bulletin board V the reaction is automatically triggered in the terminal equipment device telephone that at the bulletin board V a protocol data element RESume is sent which notifies the end of parking. The parked connection is collected by the telephone under the preset identification number (CALL IDENTITY) (eg identif ication number 7). The connection is again made by the bulletin board and the recording with RESume ACKnowledge receipted to the telephone.

In this way an automatic equipment exchange takes place so that the subscriber being dialled now takes the connection established by the PC through the telephone.

There now follows a signalling of the telephone by means of the coded request of TEls in connection with a standardconforming behaviour of the network termination (here: return 30 loop of the contents of the Dchannel in an echo D-channel) or a standard-conforming behaviour of the bulletin board (here: allocation of TEIs to the D-channel). In this way the telephone recognizes that it ought to establish the SP1791 P3 19 AuguSt 1996 connection with RESume. The standard function PARK is used in a hitherto unusual way insofar as it is used f or an automatic change of equipment. originally it was provided for a manual change of equipment.

There are numerous conceivable alternative uses of the invention. In one alternative there is a change of equipment and.service from telephone to telefax, likewise by using the PARK function. To this end f or example the standard-conforming behaviour of the bulletin board is used when allocating TEI. Through a f or example quadruple demand for a TEI a PROM arranged in the telefax recognizes after overhearing and evaluating that it is to establish the connection. With the change of equipment is connected also a change of service from telephone to faxing. A five times request f or a TEI could designate f or example a code f or the PC to react in a certain way, possibly to establish a connection.

A further application of the invention lies in informing one or more other terminal equipment devices of the ISDN connection through a communication according to the invention between the terminal equipment devices, in order to switch to an existing connection, possibly to build up a conference circuit.

A further use can be to transfer the charges arising from one conversation to another equipment.

A second method according to the invention causes a data transfer between terminal equipment devices through the direct coding of data packages or parts thereof which according to standard are sent within the scope of the ISDN SP1791.P3 19 August 1996 protocol from one terminal equipment device to the bulletin board V and/or to the network termination NT. As an example, a coding of an ID request data package will be described below in connection with Figure 5.

As already explained, a TEI is allocated to each ISDN apparatus on the basic connection of the bulletin board V. This concerns.a level-2-address. To the demand for a TEI the terminal equipment device sends a data package IIID Request" 5 on the transmission line 3 of the basic connection. This package 5 is answered by the bulletin board V with an IIID Assigned" 6 or with an 111D Denied" 6.

So that the terminal equipment device can detect whether a received data package is the answer to the actual demand and not to the demand of another terminal equipment device the terminal equipment device uses in the data package IDRequest 5 a number R, which according to the prior art is a random number. This 20 number R, is generated by the terminal equipment device and identifies same.

The number R, is reflected unchanged in standard-conforming way from the bulletin board V to the receiving line 4 of the basic connection and is read and recognized by the terminal equipment device. By listening in on the receiving line of the D-channel however this number can also be read by the other terminal equipment devices of the base connection and can therefore be used to transfer data between two terminal equipment devices. For this purpose each terminal equipment device has a coding unit 7 and a decoding unit 8.

The coding unit 7 produces the number R, so that this additionally codes data. To this end large digital numbers SP1 791.P3 19 August 1996 are formed wherein the numbers contain data at the same time. These numbers are read and evaluated in the decoding unit 6 of the other terminal equipment device. The transfer rate to be achieved in this example amounts to some octets 5 per second.

The data being transferred can contain any information, such as signals for taking over an existing connection or even simply certain data such as telephone numbers and addresses. All the aforesaid uses, such as change of equipment, change of service, setting up a conference circuit, charge-transfer etc are possible with this method which provides a direct coding of data packages or parts thereof.

In further embodiments the standard-conforming behaviour of the bulletin board is utilized when sending charge information or when requesting certain information services. The transfer of information is thereby carried out each time through overhearing such data sent out by a terminal equipment device and which is reflected from the transmission line of the signalling channel to the receiving line of the signalling channel. The data itself or the time sequence of the transmission and the type of data thereby represent a code for the transfer of information.

The invention is not restricted in its design to the aforesaid embodiments. Rather a number of variations are possible which make use of the invention even in fundamentally quite different designs.

SP1791.P3 19 August 1996 18 -

Claims

7_.

1. Method for the transfer of information between two or more standardconforming terminal equipment devices of the same ISDN telecommunications connection, which are connected by a common bus line to a standard ISDN interface and are in connection through a network termination with a bulletin board, characterised in that a transfer of information between the terminal equipment devices (TE1, TE2, TE3)takes place solely on the signalling channel and for the transfer of information between the terminal equipment devices (TE1, TE2, TE3) an internal code is used which uses as code elements protocol-conforming signalling commands of the terminal equipment devices to the bulletin board (V) or network termination (NT) wherein a) one terminal equipment device (TEl,TE2,TE3) sends at least one signalling command to the bulletin board (V) or network termination (NT), b) the bulletin board (V) or network termination (NT) reacts in a protocol-conforming way to the at least one signalling command and c) at least one further terminal equipment device (TEl,TE2, TE3) detects the protocol-conforming behaviour and accompanying signals of the bulletin board (V) or network termination (NT) to the at least one signalling command and evaluates same as code for the transfer of information.

2. Method according to claim 1 characterised in that a 30 terminal equipment device (TE1, TE2, TE3) sends standard data elements or parts thereof to the bulletin board (V) and/or to the network termination (NT) and information for another terminal equipment device is coded through the time SP1791.P3 19 August 1996 Z7.

sequence of the transmission of the standard data elements and/or the type of standard data elements or parts thereof.

3. Method according to claim 1 or 2 characterised in that standard data elements or parts thereof sent on the transmission line of the signalling channel from a terminal equipment device (TEl,TE2,TE3) are reflected in standard manner to the receiving line and are read by another terminal equipment device (TEl,TE2,TE3) whereby the transmitted standard data elements or parts thereof code information for the other terminal equipment device (TEl,TE2,TE3).

4. Method according to one of claims 1 to 3 characterised in that the standard conforming behaviour of the bulletin board (V) or network termination (NT) is used when asking for a terminal endpoint identifier (TEI).

5. Method according to claim 4 characterised in that a) a f irst terminal equipment device f or asking f or a terminal endpoint identifier (TEI) sends a data package (ID request) to the bulletin board (V) wherein the data package (ID request) has an identification number (R,) produced by the terminal apparatus and this identification number (R,) 25 codes data, b) the identification number (R,) is reflected in'standardconforming manner from the bulletin board (V) unchanged to the receiving line of the signalling channel and c) is read by a second terminal equipment device and recognized as data information.

6. Method according to claim 4 characterised in that a change of apparatus from a first terminal equipment device SP1791.P3 19 August 1996 (TEl,TE2,TE3) to a second terminal equipment device (TEl,TE2,TE3) is carried out by a) the first terminal equipment device (TEl,TE2,TU) producing a code through repeated requests for a terminal endpoint identifier (TEI) b) the first terminal equipment device (TEl,TE2,TE3) after producing this code interrupts the current transaction according to. a standard SUSPend-f unction, whereby the transaction number is released without the corresponding connection being terminated, c) the second terminal equipment device (TEl, TE2,TE3) overhears and recognizes the code produced by the f irst terminal equipment device (TEl,TE2,TE3) and d) the second terminal equipment device (TEl,TE2,TE3) then picks up again the transaction interrupted by the f irst terminal equipment device (TEl,TE2,TE3) automatically through a standard RESume function.

7. Method according to one of claims 1 to 3 characterised in that the standard-conforming behaviour of the bulletin board (V) or network termination (NT) is used during transfer of charge information, when calling up the time clock or other information services or when retrieving the service feature state.

8. ISDN telecommunications connection for carrying out the method according to claim 1 with several terminal equipment devices attached to a standard ISDN interface through a common bus line, characterised in that in the terminal equipment devices (TEl,TE2,TE3) there are:

a) means for sending out at least a protocol-conforming signalling command to the bulletin board (V) or network SP1791 P3 19 AuguSt 1996 77termination (NT) wherein the at least one signalling command represents a code or the component part of a code f or transferring information between the terminal equipment devices (TEl,TE2,TE3) b) means for detecting the protocol-conf orming behaviour and accompanying signals of the bulletin board (V) or network termination (NT) to a corresponding signalling command of another terminal equipment device and c) an evaluating unit which evaluates the protocol10 conforming behaviour and accompanying signals of the bulletin board (V) and/or network termination (NT) to signalling commands of the terminal equipment devices as internal codes for the transfer of information between the terminal equipment devices (TE1, TE2. TE3).

is 10. Telecommunications connection according to claim 9 characterised in that a coding unit (7) and a decoding unit (8) are provided to produce and recognize a code for the data transfer.

11. Telecommunications connection according to claim 10 characterised in that the coding unit (7) produces an identification number (R,) so that data to be transferred are coded in the identification number (R1) and the decoding unit (8) decodes such identification numbers (R,).

12. A method for the transfer of information between two or more standardconforming terminal equipment devices of the same ISDN telecommunications connection, which are connected by a common bus line to a standard ISDN interface are are in connection through a network termination with a bulletin board, substantially as herein described with reference to Figures 3 to 5 of the drawings.

SP1791.P3 19 August 1996 1 13. ISDN telecommunications connection for carrying out the method according to claim 1 with several terminal equipment devices attached to a standard ISDN interface through a common bus line, substantially as herein described with 5 reference to Figures 3 to 5 of the drawings.

SP1791.P3 19 August 1996