DE4407214C1 - Extending transmission path between ISDN subscriber functional gps. - Google Patents

Abstract

A protocol converter is employed which can operate in either master or slave mode with ISDN and connection interface modules (1, 2) linked bidirectionally with a clock generation module (3) which is controlled by a mode selector (5) and microprocessor (6). The network interface (2) converts specifically encoded data into binary code. The microprocessor accepts B- and D-channel data from a connecting line (a) or bus (b) for formation into blocks for X-channel transmission through the subscriber interface (2). Clock recovery at the receiver is based on either the temporal sequence of received data blocks or that of the transmitted bits.

Description

The invention relates to a method and a device for increasing the Range of the transmission path between functional units of the ISDN Subscriber connection based on an ISDN interface, such as after CCITT I.400-ISDN User Network Interface and I.430-Basic User Network Interface is standardized. This makes it possible to use the wide range of ISDN services over a wide range Transfer distances.

The ISDN (Integrated Services Digital Network), which in addition to telephony also allows fast transfer of data, text and images, gives to his Interfaces the possibility of connecting NT and TE devices and others Distribution networks.

The CCITT reference configuration according to FIG. 5 is used to functionally delimit the elements used in the subscriber line.

The functional units indicate in detail:
ET, Exchange Termination:
Network switching center carries out subscriber network signaling on the network side.
LT, line termination:
Line termination forms on the network side the transmission-related termination of the route from the switching center to the subscriber line. It is sometimes considered part of the ET and is not shown separately.
NT1, Network Termination 1:
If the transmission-related termination from LT to the subscriber connection can be controlled by the network operator, the end system connection is isolated from the transmission technology of the subscriber connection.
NT2, Network Termination 2:
If available, operator or concentrator functions in the form of a telecommunications system.
TE1, Terminal Equipment Type 1:
Corresponds to the ISDN interfaces and works directly on NT1 or NT2.
TE2, Terminal Equipment Type 2:
Is a conventional end device with an analog interface, an end system adapter (Terminal Adapter, TA) is required to operate the ISDN, which provides access to the ISDN.

This reference configuration identifies the necessary functions independently of technical details and clarifies their relative position to each other.  

Between the functional units thus formed (functional groups) Reference points that define the functional units from each other separate. The reference point V is between the exchange and Line termination, the reference point U between line termination and network termination, the Reference point T between network termination 1 and 2, the reference point S between Network termination and type 1 end system and the reference point R between the end system adapter and end system type 2. For the reference point U there are nationally standardized interfaces, There are internationally standardized interfaces for the reference points S and T.

A large number of functions can be implemented at the interfaces of the ISDN subscriber line. An S _o interface must fulfill the following functions, for example:

• - two wires (copper) for each direction of transmission;
• - Gross transmission speed of the AMI-encoded signals for each Direction 192 kbit / s;
• - Net data rate (2B + D) = 144 kbit / s (48 kbit / s for synchronization and control);
• - Step clock: derivation from the bit stream = 192 kbit / s
• - Octet clock: derived from 192 kbit / s = 8 kHz (for speech coding)
• - Frame synchronization: (realized by code violations for the purpose Recovery of time-division multiplex channels)
• - D echo channel: (serves the orderly access of the TE to the D channel)
• - Activation and deactivation (change between operating and Idle state).

Frame structure and coding of the bits to be transmitted are subject to a fixed laid rule. According to the rules of the HDLC, the information to be transported mation packed in one or more frames, each with a special whose bit sequence begins and also ends. According to defined schemes procedures such as frame synchronization, superframe control, access control, remote supply, activation and deactivation implemented.  

Regardless of a network-side connection of ISDN terminals (TE) or network terminations (NT), it is advantageous to extend the range of the transmission path between functional units of the ISDN subscriber connection based on an ISDN base connection S _o or another ISDN interface in order to extend the to be able to pass on information in a network over a longer distance. However, the range that can be achieved with conventional means is considerably restricted due to the electrical properties of the ISDN interfaces and connection paths. So far, it has not been possible, for example, to operate an S _o interface over more than 1000 m (point-to-point connection) or a U _ko interface without the interposition of amplifiers over more than 6 km. This means that the range of the transmission path between the functional units of the ISDN subscriber line in relation to an ISDN interface is limited.

According to the CCITT I.400 standard, the signal delay is e.g. B. between the functional units NT and TE and back between a minimum of 10 µs and a maximum of 14 µs fixed. The 2-bit frame offset plays a role here Clock recovery is used (frame offset = code violation as an indicator for the beginning of the frame).

To detect a collision, the beginning of the frame (2 bits) must be approximately 70% of the Signal runtime can be recognized.

• - for 2 bits = 10.416666 µs
• - with reply = 3.6458331 µs.

Assuming a wave attenuation of 7.6 dB / km for copper, this is Signal transit time T = 9 µs / km. This results in

for the maximum expansion of the S _o connection. This calculation applies in the case of point-to-multipoint configuration. The calculation for the point-to-point configuration (no collision detection) results in an analogy of 1 km.

The time relationships for transmission over a satellite channel with regard to collision detection do not change. However, the signal runtime changes when connected via a geostationary satellite (36,000 km). This is 220 ms in one direction and 440 ms with response. These time relationships show that a direct extension of the range of the transmission path between functional units of the ISDN subscriber line starting from a base connection S _{o is} impossible in this way.

The object of the invention is therefore to create a method and a device, which allow the range of the transmission path between functional units the ISDN subscriber line to enlarge. This while maintaining all ISDN typical features such as:

• - Maintaining the network clock
• - Multiple access to the interface bus
• - Activation and deactivation of the interface.

According to the invention the object is achieved by a method in which

• a) the data is sent on the network side so that the on the ISDN interface accumulated ISDN-specific encoded data using a code converter in binary coded data converted to B and D channel information separately become,
• b) from this accumulating data of the B and D channels by means of a memory device blocks are formed in from the ISDN-specific clock  ISDN interface derived time intervals the transmission means leads and transmitted to the recipient side via this,
• c) a clock jerk on the receiver side assigned to the terminal is provided, either from the chronological order of the received data blocks or from the chronological sequence of the transmitted Data bits necessary for the communication between sender and receiver ISDN-specific clocks are recovered, and
• d) the blocks received are temporarily stored in a memory device and then the B-channel information according to the return clock and the D-channel information, if available, a code converters are fed and
• e) the data is sent on the terminal side analogously to method steps a) and b), and
• f) data recovery on the receiver side assigned on the network side by means of a code converter in accordance with the ISDN specific clock occurs.

The block is preferably formed after step b of the method in such a way that the blocks formed are of equal length and have B-channel and D-channel data Division ratio, which is the ratio of the capacities of B- and D- Corresponds to channels of the ISDN interface.

The blocks are formed when the D channel carries no information of the same length without D channel data.

An active intervention in the D-channel signaling takes place in cases where the Signal runtime of the D-channel signaling via the transmission channels used is great. In these cases, the activating participant is signaled that the Connection has not yet been established.  

The length of the blocks formed according to method step b depends on the capacity the processing units for converting, transmitting and converting the ISDN Interface information and the ISDN-specific channel capacities.

The blocks thus formed are transferred using known transmission devices Satellite or other transmission channels transmitted.

The clock recovery after step c of the method takes place when that Transmission system determines the transmission clock itself, in the form that from the a comparison clock is obtained in the chronological sequence of the received data blocks, by means of a phase-look-loop (PLL) according to known principles Basic clock is generated, from which the clock for the ISDN Interface is derived on the terminal side.

If the bit clock for the transmission system by a realizing the method Device can be specified, this basic clock is preferred for the ISDN interface recovered from the bit transmission clock using PLL.

Both the terminal and network-side conversion of the ISDN-specific encoded data into binary-coded data is carried out according to known principles using a code converter, preferably an ISDN subscriber access controler.

According to the invention, the method for increasing the empire is implemented distance of the transmission path between functional units of an ISDN subscriber connection by a device that is both terminal and network side from one Protocol converter and this assigned transmission channel.

The transmission channel consists of known transmission devices and the medium used for transmission, e.g. B. a satellite channel with the ent speaking transmitting and receiving devices and the necessary Modems.  

The protocol converters communicate via the respectively assigned transmission channel together. The protocol converters are preferably constructed identically and can act both in the master mode and in the slave mode, the network side in each case connected protocol converter in master mode and the terminal protocol converter works in slave mode. It is also possible to set up the protocol converter exclusively in master or slave mode, one on the network side in master mode working protocol converter and a protocol working in slave mode on the terminal side converter must be available.

The protocol converters essentially consist of
an ISDN interface module ( 1 ),
an interface module ( 2 ) for connection to transmission channel X,
a module for clock generation ( 3 ),
a power supply ( 4 ),
a switch for mode setting (master / slave) ( 5 ),
a microcomputer ( 6 ) and
corresponding electrical connections.

The microcomputer ( 6 ) is connected via a bus (b) or additionally via a bit serial data line a to the ISDN interface module ( 1 ) and via the bus (b) to the interface module ( 2 ) for connection to the transmission channel X.

The clock generation module ( 3 ) is connected to the interface module ( 1 ) via line (d), the microcomputer ( 6 ) via line (e) and to the interface module ( 2 ) for connection to the transmission channel X via line (c).

The switch ( 5 ) for the mode setting (master / slave) acts on the power supply ( 4 ), on the interface module ( 1 ), on the module ( 3 ) for clock generation and on the microcomputer ( 6 ).

The power supply ( 4 ) supplies the circuit with voltage and, when the protocol converter is operating in slave mode, generates the supply voltage for network-independent devices.

The ISDN interface module ( 1 ) electrically converts the ISDN interface into a binary-coded form and vice versa. The binary data and the necessary control information are exchanged via the bus (b) between the interface module ( 1 ) and the microcomputer ( 6 ). The ISDN interface module ( 1 ) is made up of an ISDN interface interface and a circuit for converting the ISDN-specifically coded data into binary-coded data, for example an ISDN subscriber access controller.

In the master mode, the ISDN interface module ( 1 ) supplies signaling information for the microcomputer ( 6 ), by means of which the microcomputer ( 6 ) can control the data exchange with the interface module ( 1 ) or clocks from which the clocks are generated in the clock module ( 3 ) that are required for data exchange via line (a) between the microcomputer ( 6 ) and the interface module ( 1 ).

In slave mode, the clocks for data exchange between the microcomputer ( 6 ) and the interface module ( 1 ) are generated by the clock module ( 3 ) from the comparison clock supplied by the microcomputer ( 6 ). Likewise in slave mode, the clock module ( 3 ) generates a basic clock which is passed to the interface module ( 1 ). The interface module ( 1 ) forms the base clock for the transmission on the ISDN interface.

The microcomputer ( 6 ) takes over the B and D channel data that are provided by the interface module ( 1 ) via the bus (b) and forms blocks that are transferred to the interface module ( 2 ) for transmission on the transmission channel X.

The microcomputer ( 6 ) accepts the blocks received in the interface module ( 2 ) from the transmission channel X into its internal working memory and transfers the B and D channel data to the interface module ( 1 ) for transmission on the ISDN interface.

In master mode, the protocol converter activates the ISDN interface again and again new if this is not active. It only transmits blocks if the ISDN Interface is active.

In slave mode, the protocol converter reactivates the ISDN interface when this is not active and the protocol converter also simultaneously blocks of data from the master Device receives. It deactivates the ISDN interface if there is no one for a second Blocks from the master device.

If the protocol converters are designed exclusively in slave or master mode, they consist of almost the same modules as listed above. There is no switch ( 5 ) for the mode setting. The other modules are switched so that they perform the functions in slave or master mode as stated above.

It is with the method according to the invention and the device according to the invention possible, the various services of ISDN via the corresponding interfaces parallel over long distances in accordance with the existing ISDN channels admit without having to move to another network. A stay in the used ISDN network is made possible, which does not affect the quality of the transmission services is affected.

Exemplary embodiments of the invention will be described in more detail with reference to the attached drawings explained. Show

Fig. 1 is a block diagram of a protocol converter

Fig. 2 representation of an ISDN interface extension

Fig. 3 is a block diagram of a protocol converter in the master mode

Fig. 4 is a block diagram of a protocol converter in slave mode.

In Fig. 1, the structure of a protocol converter, which can work both in the master and in the slave mode, is shown as a block diagram. The protocol converter consists of the modules ISDN interface module ( 1 ), interface module ( 2 ) for connection to transmission channel X, module for clock generation ( 3 ), power supply ( 4 ), switch for mode setting (master / slave) ( 5 ) and microcomputer ( 6 ), whereby the individual assemblies, as already mentioned, are interconnected and function in the master or slave mode.

Connected to the mains, the protocol converter works in master mode, connected in slave mode in the terminal. The setting is made via switch ( 5 ).

Connected to the network, the protocol converter converts the specifically coded data accumulating at the ISDN interface into binary-coded data using the interface module ( 1 ). The microcomputer ( 6 ) takes over the B and D channel data, which are provided by the interface module ( 1 ) via the bus (b) or via the connecting line (a) and the bus (b) and form blocks from them to the Interface module ( 2 ) to be transferred to transmission channel X. For this purpose, the interface module ( 1 ) supplies the signaling information for the microcomputer ( 6 ) or clocks, from which the clocks are generated in the clock module ( 3 ) for the data exchange via line (a) between the microcomputer ( 6 ) and the interface module ( 1 ). are needed.

Connected on the terminal side, the protocol converter recovers the ISDN-specific clocks necessary for the communication between sender and receiver from the time sequence of the received data blocks and the clock of the received data bits. In the RAM of the microcomputer ( 6 ), the blocks received are buffered and converted into an ISDN-specific code via the interface module ( 1 ) in accordance with the recovered clock and passed to the ISDN connection on the terminal side.

If the data is sent on the terminal side, the interface module ( 1 ) converts the ISDN-specific data into binary-coded data, forms blocks via the microcomputer ( 6 ) and passes them on to the transmission channel X via the interface module ( 2 ) the received data are temporarily stored in the RAM of the microcomputer ( 6 ) and the temporarily stored data are transferred to the ISDN interface in accordance with the clock specified by the ISDN interface, the interface module ( 1 ) converting them back into ISDN-specific coded data.

Fig. 2 is an apparatus to increase the range of the transmission channel between functional groups of the ISDN user interface with respect to a S _o - interface again. Starting from a network ISDN, via an interface U _ko to a network termination NT, a protocol converter PW is arranged on the network side at the interface S _o , which communicates with a protocol converter PW via a transmission channel at the terminal end and provides the interface S _{o at the} terminal end. On the terminal side, a switching system (NT2) or terminal devices (TE) can then be operated, for example.

The device connected on the S _o network side works in master mode, the device connected on the S _o terminal side works in slave mode. The device working in master mode behaves towards the ISDN network like a terminal (TE), the device working in slave mode like a network termination (NT).

Between two protocol converters (PW) connected via the transmission channel the data exchange takes place by means of bit serial synchronous transmission of data blocks of 16 B-channel bytes each plus a maximum of 2 D-channel bytes.

The protocol converter PW in master mode always reactivates the S _o interface when it is not active. It only transfers blocks when the S _o interface is active.

The protocol converter PW in slave mode reactivates the S _o interface when it is not active and the device also receives data blocks from the master device. It deactivates the S _o interface if it does not receive any blocks from the master device for one second.

According to the invention, it is also possible to enlarge the transmission path between functional units of the ISDN subscriber line in relation to a U _ko interface. In this case, the protocol converter connects to this interface with an assigned transmission device.

Fig. 3 shows a block diagram of a protocol converter in master mode. The designation of the assemblies shown corresponds to that in FIG. 1, the individual assemblies being constructed as follows and interacting functionally.

The interface module ( 1 ) consists of an S _o interface ( 11 ) and a PEB 2086 ( 12 ) circuit designed as an ISDN subscriber access control module.

In the interface module ( 1 ), the mutual conversion of the signal levels from the interface S _o to the signal levels required by the module ( 12 ) takes place in the S _o interface ( 11 ).

The interface module ( 2 ) consists of a SAB 82532 circuit designed as an SIO module ( 21 ) and a common interface ( 22 ) for the X channel.

The mode setting causes the module ( 12 ) in the interface module ( 1 ) to switch to TE mode (terminal mode). In this mode, the PEB 2086 ( 12 ) derives synchronous clocks from the interface S _o and below that a clock of 1536 KHz especially at the output CP, from which a transmit clock TxCL of 192 KHz is divided by 8 times in the module for clock generation ( 3 ) is produced. The clock TxCL is forwarded to the interface module ( 2 ).

The microcomputer ( 6 ) consists of a microprocessor 80C188 XL-20 ( 61 ), a ROM for storing the program code, a RAM as working memory and a BUS. Via the extended bus b of the microcomputer ( 6 ), it is connected to the PEB 2086 ( 12 ) in the interface module ( 1 ) and to the SIO block SAB 82532 ( 21 ) in the interface module ( 2 ).

The processor ( 61 ) in the microcomputer controls the function of the components PEB 2086 ( 12 ) and SAB 82532 ( 21 ) in a known manner by setting the registers provided in these components. The processor in the microcomputer ( 6 ) also queries the state of these components and exchanges data via registers of these components.

The S _o interface is activated / deactivated by the PEB 2086 ( 12 ) in the interface module ( 1 ) of both devices in a known manner. The state of the S _o interface can be read from the registers of PEB 2086 ( 12 ). The processor in the microcomputer ( 6 ) cyclically polls the registers of the PEB 2086 ( 12 ), which indicate the status of the S _o interface.

The connected S _o interface is activated by register setting of the PEB 2086 ( 12 ) if it is not active for a certain time (more than 1 second).

The functions described below are only carried out when the S _o interface is active:

The PEB 2086 in the interface module ( 1 ) converts the ternary coded B and D channel signals from the interface S _o into binary coded signals and stores them byte by byte in the known registers. Conversely, the module ( 12 ) converts the binary-coded B and D-channel bytes entered by the processor into ternary signals and sends this data to the S _o interface for transmission on the interface S _o .

The PEB 2086 ( 12 ) signals by means of a register when a complete B-channel byte is ready to be taken over by the processor ( 61 ). The processor ( 61 ) polls the signaling register of the PEB 2086 ( 12 ) cyclically and takes the finished B-channel bytes into its RAM.

The PEB 2086 ( 12 ) uses another register to signal when a D channel frame has been received by S _o . The processor also polls this signaling byte cyclically and, if necessary, takes over the D-channel frame on its RAM.

If the processor has transferred a block of 16 B-channel bytes to its RAM from the PEB 2086 ( 12 ) in the interface module ( 1 ), this block is transferred to the SAB 82532 ( 21 ) in the interface module ( 2 ). If at this point in time a D-channel frame is temporarily stored in the RAM of the processor ( 61 ), the next maximum of two D-channel bytes of the frame that have not yet been forwarded are also sent to the SAB 82532 ( 21 ) and then set a control register in SAB 82532, which causes this block to transfer this block of at least 16, maximum 18 bytes via the X-channel interface to the device in slave mode on the other side of the X-channel to start.

The data is transmitted using the clock TxCL provided by the clock generation module ( 3 ).

In the opposite direction, the SAB 82532 ( 21 ) receives bit serial data in the interface module ( 2 ) via the X-channel interface with the transfer clock RxCL, which is the send clock of the device in slave mode on the other side of the X-channel. If a complete block has been received in SAB 82532 ( 21 ), a signaling register is set in SAB 82532. The processor of the microcomputer ( 6 ) polls this register cyclically. If the receipt of a block is indicated, the processor adopts this block in its RAM. The 16 B-channel bytes of the last 4 blocks received are buffered in the RAM.

The B-channel bytes are forwarded to the PEB 2086 ( 12 ) in the interface module ( 1 ) with an average delay of 4 by 16 bytes based on the time of their receipt.

The PEB 2086 in the interface module ( 1 ) signals via internal registers that a B channel byte is to be transferred to the PEB 2086 for transmission to S _o . The processor of the microcomputer ( 6 ) polls this register cyclically and then transfers the B bytes accordingly to the PEB 2086.

The D-channel bytes in the blocks received by the interface module ( 2 ) are transferred to the known D-channel registers of the PEB 2086 in the interface module ( 1 ) without intermediate storage.

If a block without D-channel bytes is received after a block with D-channel bytes, this means the end of a D-channel frame. The processor then sets the appropriate control register in PEB 2086, causing PEB 2086 to transfer this D-channel frame to the S _o interface.

Fig. 4 shows a block diagram of a protocol converter in slave mode. The designation of the assemblies shown corresponds to that in FIG. 1, the individual assemblies being constructed as follows and being functionally connected.

In the interface module ( 1 ), constructed analogously to FIG. 3, the mutual conversion of the signal levels from the interface S _o to the signal levels required by the block PEB 2086 ( 12 ) takes place in the S _o interface.

The mode setting means that the PEB 2086 module in the interface module ( 1 ) is switched to NT mode (network terminal mode). In this mode, the PEB 2086 requires synchronous clocks at the DCL inputs of 512 KHz, FSC1 and FSC2 of 8 KHz. From these, the PEB 2086 derives the frame synchronous and bit synchronous clocks for the interface S _o .

The clocks required by the PEB 2086 in the interface module ( 1 ) are generated in the clock generation module ( 3 ) from the clock RxCL of 192 KHz received by the interface module ( 2 ) by means of a phase locked loop PLL operating according to known principles.

Microcomputers ( 6 ), PEB 2086 in the interface module ( 1 ) and SAB 82532 in the interface module ( 2 ) work together in an analogous way as in the master device, in the forwarding of the B and D channel data between the S _o interface and X channel.

Deviating from the master device, the S _o interface is deactivated if no blocks are received from the X channel. The S _o interface is reactivated when blocks are received again.

The power supply ( 4 ) of the device generates a DC voltage of 40 V for the power supply of a connected TE without its own power supply, which is forwarded to the TE via the S _o interface.

Claims (10)

1. Method for increasing the range of the transmission path between functional units of the ISDN subscriber line in such a way that

• a) the data is sent on the network side in such a way that the ISDN-specific coded data arriving at an ISDN interface are converted into binary-coded data separately for B and D channel information by means of a code converter,
• b) blocks are formed from this accumulating data of the B and D channels by means of a memory device, which are supplied to the transmission means at time intervals derived from the ISDN-specific clock of the ISDN interface and are transmitted via this to the receiver side,
• c) on the receiver side assigned to the terminal, a clock recovery means is provided which, either from the chronological sequence of the received data blocks or from the chronological sequence of the transmitted data bits, recovers the ISDN-specific clocks necessary for the communication between transmitter and receiver, and
• d) the blocks received are temporarily stored in a memory device and then the B-channel information corresponding to the recovered clock and the D-channel information, if present, are fed to a code converter and
• e) the data is sent at the terminal analogously to method steps a) and b), and
• f) on the network side of the receiver side, the data is recovered by means of a code converter in accordance with the ISDN-specific clock specified on the network side.

2. The method according to claim 1, characterized in that the block formation according to step b of the method is such that the blocks formed are the same Have length and B-channel and D-channel data have a division ratio, which corresponds to the ratio of the capacities of B and D channels. 3. The method according to claim 1 or 2, characterized in that according to step b blocks of the same length without D channel data were formed in the times in which the D channel carries no information. 4. The method according to claim 1 of the method, characterized in that the Clock recovery after step c of the method in the event that the Transmission means determines the transmission clock itself, takes the form that a comparison clock from the chronological sequence of the received data blocks is obtained, by means of which a basic cycle is generated according to known principles and from which the clock for the ISDN interface is derived on the terminal side. 5. The method according to claim 1 of the method, characterized in that at Specification of the bit clock by a device implementing the method Clock recovery after step c of the method from the bit transmission clock he follows. 6. The method according to claim 1, characterized in that at an over means of exceeding the ISDN standardized signal delay due to the means of transport the D-channel signaling is signaled to the activating subscriber that the connection has not yet been established.   7. Device for increasing the range of the transmission path between functional units of the ISDN subscriber line, characterized in that it consists of protocol converters connected to the terminal and network side with ISDN interfaces and the associated transmission channel consisting of the transmission device and transmission medium, the protocol converter both in the master and also slave mode or in master or slave mode, whereby the network-connected protocol converter works in master mode and the terminal-connected protocol converter works in slave mode and the protocol converter communicates with each other via the assigned transmission channel, so that the protocol converter essentially consists of an ISDN interface module ( 1 ), an interface module ( 2 ) for connection to the transmission channel (X), a module for clock generation ( 3 ), a power supply ( 4 ), a switch for mode setting (master / slave) ( 5 ) There is a microcomputer ( 6 ) and associated electrical connections, the microcomputer ( 6 ) via a bus (b) or additionally via a bit-serial data line (a) with the ISDN interface module ( 1 ) and via the bus (b) with the interface module ( 2 ) is connected for connection to the transmission channel (X), the module for clock generation ( 3 ) with the interface module ( 1 ) via line (d), the microcomputer ( 6 ) via line (e) and with the interface module ( 2 ) for connection to the transmission channel (X) via line (c), the switch ( 5 ) for mode setting (master / slave) with the power supply ( 4 ), the interface module ( 1 ), the module ( 3 ) for clock generation and the microcomputer ( 6 ) is in operative connection, the power supply ( 4 ) supplies the circuit with voltage and, when the protocol converter is operating in slave mode, generates the supply voltage for network-independent end devices, the ISDN interface enmodul ( 1 ) converts the ISDN-specific data into a binary-coded form or vice versa, and supplies the signaling information for the microcomputer ( 6 ) in the master mode and the module ( 3 ) for clock generation in slave mode provides the clocks for data exchange between the microcomputer ( 6 ) and Interface module ( 1 ) generated by the clock module ( 3 ) from the comparison clock supplied by the microcomputer ( 6 ). 8. The device according to claim 7, characterized in that the interface module ( 1 ) from an interface interface ( 11 ) and a circuit ( 12 ) for converting the ISDN-specific coded data into binary coded data is constructed. 9. The device according to claim 7, characterized in that the interface module ( 2 ) consists of a circuit designed as an SIO module ( 21 ) and an interface ( 22 ). 10. The device according to claim 7, characterized in that the module for clock generation ( 3 ) is constructed as a PLL circuit.