Digital message transmission system

The invention relates to a digital messaging system according to the preamble of Patent Claim first

It is known, such a system, which is used for multiple use of a two-wire subscriber line in the telephone network (DE-OS 2,758,109). In this system, various voice and data channels are transmitted in time division on the connecting line between the terminal of a subscriber and the subscriber line circuit in the associated switching center. Transmission occurs at a rate (also: bit stream or bit rate) of 192 kbit / s.

If larger distances between the exchange and the subscriber to be bridged with the known system, it is necessary either to install special connecting lines or use repeaters to ensure the required transmission quality. The laying of new lines or the use of repeaters but requires high investment funds.

From "Telcom Report", Volume 2, Issue 4, July 1979, p 258, middle column is also known to transmit voice and signaling adjacent to channels with different bandwidths.

The invention has for its object to provide a digital communication system that enables delivering flawless simultaneous transmission of voice and data over conventional telephone-line connection.

This object is achieved by the designated in claim 1. messaging system.

Advantageous developments of the invention are characterized in the dependent claims.

One advantage of the invention is that the same time synchronizing and Signalisierzeichen and data can be transmitted with a smaller bit rate over an auxiliary channel on the same line. In addition, the bit error rate, ie, the probability that a bit is corrupted during the transmission, in the system according to the invention very small. The main channel may optionally be used to transmit speech or data, the auxiliary channel can be used simultaneously and independently from the main channel for transmission of data.

An embodiment of the invention will be explained below with reference to the drawing. It shows<ul><li>Fig. 1, the time division multiple channels formed in the messaging system according to the invention in a schematic representation,</li><li>Fig. 2 shows the allocation of the numbers of the via lead transmitted bits to the individual in FIG. 1 apparent channels,</li><li>Fig. 3 shows the structure of the time-division-multiplex frame used in the messaging according to the invention,</li><li>Fig. 4 shows the subscriber side terminal of the messaging system according to the invention as a block diagram,</li><li>Fig. 5, the terminal apparatus according to Fig. 4 showing the individual data and control line,</li><li>Fig. 6, the exchange side (subscriber) interface circuit, shown as a block diagram,</li><li>Fig. 7 shows the connection circuit of Fig. 6 showing the individual data and control lines,</li><li>Fig. 8, the terminal can be connected auxiliary equipment for data transmission via the main channel and for data transmission via the auxiliary channel, in a schematic representation</li><li>Fig. 9, the central unit and the conversion unit of the terminal apparatus according to Fig. 4 and Fig. 5, and</li><li>Fig. 10, the central unit of the connecting circuit of FIG. 6 and FIG. 7.</li></ul>

The subscriber-side terminal 1 of a digital messaging system according to the invention includes a telephone set 2, in which the analog voice signals by a suitable method - eg by Pulscodemodulatin (PCM) -. Digitized and the digital signals are displayed in a main channel HKA. The necessary for building and operating a communication link digital SIGNALLING and synchronization characters are displayed in an auxiliary channel for signaling and synchronization ZKS. The terminal equipment may also be provided with a data terminal unit 3 of any type whatsoever, as indicated by a switch 5, can be selectively connected to the messaging system, and the digital message signals are then transmitted in place of voice signals on the main channel HKA, while the SIGNALLING and idle characters also input to the additional channel ZKS or read from him.

The terminal device may further include another data terminal 7, supplies the digital data signals with low bit rate. The bit stream is shown in an additional channel for data ZKD, entered the signaling bits in the auxiliary channel for signaling. During the transmission of voice or data in the main channel HKA can only individually, another data transmission can simultaneously and independently of the connection on the main channel will be carried out via the auxiliary channel.

In the illustrated embodiment, the gross bit stream or gross bit rate of the main channel HKA be - as indicated in the drawing - 64 kbit / s, which of the additional channel for signaling and synchronization ZKS 8 kbit / s and the additional channel for data ZKD also 8 kbit / s.

The different bit streams are interleaved in time in a time-division multiplex circuit 9 and get 80-kbit / s stream via a subscriber line 11 to an exchange-end time-division multiplex circuit 13, in which the bit streams of the main channel HKA, the additional channel for signaling and synchronization ZKS and the additional channel be separated again for data ZKS. In data transfer in the reverse direction, ie from the exchange to the terminal device, the time-division multiplex circuit 13 operates as a multiplexer, while the time division multiple circuit 9 acts as a demultiplexer, that the bitstreams separated.

Via a subscriber-line interface circuit 15, the connection line 11, and thus the single terminal 1 is connected to the associated telephone exchange (not shown in the drawing) and connected via these with the further telephone network. From the terminal 1, the communication signals and the control characters move through the main channel HKA or via the auxiliary channel for signaling and synchronization ZKS to the connection circuit 15. This includes a basic version 16 and can also with an ancillary service facility 17 may be provided that the terminal a manufactures data network, eg. as to the Integrated data network IDN or the data packet switching network DPVN. The data exchange between the terminal 7 and the ancillary service facility 17 via the auxiliary channel for data ZKD, the signaling and synchronization also takes place via the auxiliary channel ZKS.

About the ancillary service facility, the connection to the local videotex Central BT-Z is produced. It can connect to the videotex center via the auxiliary channel ZKD be handled while on the main channel HKA a long distance call is made. In contrast to conventional analog local loop telephone line is not blocked by a screen text connection. In addition, sufficient capacity for transferring Signalisierzeichen for more to be realized in future services and features available.

Fig. 2 shows an advantageous structure of the word via the connection line 11 transmitted digital signals, ie, the assignment of the individual bit numbers to the different channels. The bits number 1 to 8 of each word are the main channel HKA, the bit number 9 the additional channel ZKS for signaling and synchronization and the bit assigned number 10 the auxiliary channel ZKD for data. The word time is 125 ps, the word sequence frequency of 8 kHz.

While on the bit number within a word, the channels are identified, the bit string is resolved in the transmission channel in words using the 3 visible from FIG. Frame structure. A frame contains 32 words with 10 bits and thus the frame length is 320 bits.

The frame duration is 4 ms and it arises in a word repetition rate of 8 kHz, a frame rate of 250 Hz.

As shown in FIG. 3 can also be seen, the bit number 9 of the words number 1 to number 8 a frame for frame synchronization and the bit number 9 is the number words provided 9 to 32 a framework for the signaling.

Signaling characters formed from the bits mentioned above are used for power control, ie for exchanging signals with the switching devices, and to exchange information with special service facilities and additional services.

Unlike the conventional analog local loop, to be signaled in the usually states ( "events" so-called.) Are in the messaging system according to the invention events, ie state changes signatisiert. The signaling characters are in the additional channel ZKS, ie transferred outside the speech band. The only exception is the audible tones. A signaling word is divided into three fields of 8 bits (octets): a header field, a character field and a safety field.

The subscriber-side terminal 1 (Fig. 4) includes the telephone set 2 with the following basic functions a: a speech circuit with an earpiece 21 and a microphone or transmitter capsule 23, a hook switch 25, a selector 27 with 16 keys, a number display 29 16 Ask and Tonrufgeneratqr 31st

The speech circuit 20 (see FIG. FIG. 5) includes a handset, not shown in the drawing, which is equipped with the dynamic earpiece 21 and the dynamic opening capsule 23, and a matching circuit 33, which represents the interface to a conversion unit 35. The matching circuit 33 causes the information required by the telephone management transmission system values ​​as reference attenuation, side tone, frequency response, etc., as well as the transfer level at the Schnittstelle.eingehalten be.

The hook switch 25 accepts the one hand the function of the subscriber status message by turning on and off the power supply and - as a consequence - initiating the synchronization phase in the digital subscriber circuit.

The conversion unit 35 includes a codec (encoding and decoding circuit), a filter and a latch. The power consumed by the microphone 23 language is band-limited by the filter with low-pass behavior, digitized and according to a CCITT_- Recommendation for PCM in 8-bit words encoded. The encoded words are correct time retrieved from a subscriber-side central unit 37 and displayed in the outgoing line of a serial data bus 39, which is also referred to as 10-bit bus.

In the receive direction, the 8-bit words by means of a control clock of the central unit 37 are hidden from the 10-bit channel and written into the latch of the conversion unit 35th There, the 8-bit PCM words are then available for a continuous digital / analog (D / A) conversion available. Then the analog signal is said band-limited and, on the earpiece 21st The conversion unit 35 is in the idle and off on calling from the power supply.

Apart from the above functions, separates the hook switch 25 when you lift the handset a Rufempfangschaltung in the central unit 37 and switches simultaneously the speech circuit 20 and containing the codec conversion unit 35 on or hanging up the handset from.

The selector 27 includes besides the usual dialing keys 1 through 0 to key the telephone numbers, which causes a direct entry of dialing information in the central unit 37, a key for the charging indicator, a button for the time display and four buttons for any to be provided special functions.

The number display 29 has a display 16ziffriges with corresponding drive circuit. The display is driven by means of coded Signalisierwörter, carried out their evaluation in the central unit 37th You can display z. B. the time, the fees, that chosen by the subscriber number or the phone number of the calling party.

The subscriber-side terminal 1 also includes a directional separation unit 41 and provided with an occupant detection circuit power supply unit 43. In the inoperative state, the circuit parts of the terminal are de-energized, ie the power is turned off. The activation of the power supply from the inoperative to the operating state is determined by the occupant detection circuit (so-called a. Bitstream detector) carried out. This circuit, which only has a very low power requirement at rest, the occupancy case the power is on and either:<ul><li>- Triggered by the bit stream sent by the switching center, or</li><li>- Triggered by pressing the hook switch when you lift the handset, or</li><li>- Triggered by switching on a connected to the digital terminal accessory.</li></ul>

The central unit 37 in the terminal apparatus 1 has the following problem: synchronizing the subscriber terminal 1, the absorption and release of signaling signals, controlling the conversion unit 35, in particular their codec, and controlling the auxiliary devices 3, 7, to the in Figure . 4, only the interface is displayed (see. also Fig. 8).

Details of the occupancy sensor and the power supply unit 43 can be taken from DE-OS 2,940,617.

The central unit 37 and the other circuit parts of the subscriber terminal, including the telephone set 2, are interconnected by the data bus 39 as well as by control lines 47, on / off lines 49 and priority lines 51, indicated by different graphic representations (cf. Fig.. 4 below), respectively.

The Tonrufgenerator 31 is operated with direct current. He is after activating the remote-controlled power and occupancy detection unit 43 on and off by means of a transmitted in the signaling channel ZKS and decoded in the central unit 37 call-control character.

The terminal 1 is prepared for modular expansion. This is achieved, inter alia by the fact that the data channel 39 is formed as a serial 10-bit bus. At an interface formed by the data bus and control and signal lines, the subscriber device - as already mentioned - by an additional device 3, 7 and also through a supplementary or comfort features 53 extended with additional features. As examples of the comfort features an extended alphanumeric keypad, an alphanumeric display and moreover a special keypad may be mentioned (not shown).

From Fig. 5, in which the circuit components of the terminal equipment having the same reference numerals as in Fig. 4, the individual lines to the various interfaces are visible. Unlike the remotely fed from the exchange of power supply of the basic equipment the auxiliary devices 3, 7 and 53 Komfortausstattung be locally powered from the 220 V mains.

Data active (for signaling of the additional device) AK, released (for signaling of the additional device) FR, bit timing TB, frame timing TR, word clock TW, coming: At the interface to the optional auxiliary devices 3, 7 and comfort features 53 following lines are provided (in binary code) DE, continuous data (in binary code) DA, turning off the codec CA and power on / off STZ.

At the interface 11, in the case of a symmetrical two-wire connection, as shown in Fig. 5, the a and b wires of the subscriber line 11 is present. With symmetrical four-wire connection, as it can be used for example in a large distance between the subscriber and the switch, the interface is the c-, d-, formed E and F veins of lead 11th

The interface 111 between the telephone set and the operation of the terminal apparatus 1 has the following lines of: analog input AI, analog output AA, power on / off (the hook switch from) STG, start / stop for the ring tone R, a quadruple line DT for the data input from the keyboard and a control line "strobe" to the keyboard 27, a quadruple data line DD and a control line "strobe" to the numeric display 29. the interface IV has the following lines on bit clock TB, system clock TS, word clock TW, coming data in binary code DE and continuous data in binary code DA.

The interface V contains the following lines: unbalanced interface connecting line g, present on the data in the line code; Power on / off of the auxiliary device of STZ and from the central unit 37 of STZ, power on / off the hook switch from STG. In four-wire connection, this interface contains instead of the line g i a line for incoming data, wired in line code and a line j for continuous data asymmetrically in the line code.

The interface VI has the following lines: a codec CE, Reading (PCM word) L, letter (PCM word) S, bit timing TB, converter clock (eg 128 kHz.) TK and word clock TW.

In the following, details of the function of the terminal apparatus 1 according to FIGS. 4 and 5 will be explained. The space required for the basic equipment of the terminal operating current is coupled via a contained in the power supply unit 43 Auskoppelübertrager between the a and b wire of the subscriber line, with a constant operating voltage is set by a shunt regulator.

The power supply unit 43 includes, as already mentioned, an occupancy detector, which is recognized by a bit stream on lead eleventh It is a receiver with high input impedance and threshold. The required low quiescent current as the occupancy detector from this condition still unloaded decoupling device - in this case the shunt regulator is not effective.

In idle state, no current flows through the connecting line 11, with the exception of low quiescent DC for the occupancy detector. The power supply for all other units is turned off. They can be turned on by the participant, of the auxiliary devices 3, 7 or from the bit stream detector (interface lines STG and STZ).

With the Auskoppelübertrager the power supply unit 43, the required electrical isolation and level adjustment between the connecting line 11 and the subscriber terminal is performed. Within the terminal apparatus 1 of the transmission path is performed asymmetrically (interface line g in Fig. 5).

The terminal 1 is protected by a protective device in the power supply unit 43 to possibly occurring on lead 11 surges.

The power unit for a four-wire connection is different from the above-described power supply unit 43 in that in their power via a respective Auskoppelübertrager from the C, D and E, F veins is coupled out, and that the bit stream detector to bitstream on c- and d-vein monitored.

The direction of separation unit 41 can either be designed for a two-wire connection and include a device which operates according to a time or a frequency division multiplex method or a DC location process, or it can be provided for a four-wire connection, in which both directions of transmission are performed in space division multiplex ,

In the Richtungstrennungseinheit41 the line coding is performed. The space required for the line coding coming bit clock is recovered by bit synchronization and is also available for the central unit 37 available. on the other hand the continuous bit clock provides the central unit 37th

For direction separation process in a two-wire connection, the following applies. Regarding the interface V (Fig. 5) is in principle to distinguish between three types of direction separation process: the time division method, the Gleichlage- and the frequency division multiplex method. In the first type, the signals come in bunches (called in. "Bursts") to, among other species in continuous form.

The direction of separation unit 41 is connected via the interface line g and the transformer contained in the power supply unit 43 with the lead 11th It contains not only the actual direction separation unit still line encoder and decoder as well as line drivers and receivers with the required pulse shaping or equalizers.

The required in the terminal 1 bit clock is derived in the direction of separation unit 41 from the incoming bit stream from the connection line and is provided on the interface line TB of the central unit 37th

The decoupled from the connecting line 11 coming data are prepared in the direction of separation unit 41 so that they are in binary form and synchronously and in phase with the next bit clock TB at the interface line DE available. The system clock also comes from the direction of separation unit 41 to the central unit 37. The word clock in the outgoing direction is 37 provided via the line TW from the central unit, in continuous form.

The hiding of continuous data in the 10-bit channel is controlled in terminal 1 or in the accessory device 3, 7 from the central unit, that they are in sync and in phase with the bit clock to the interface line DA available.

In the case of message transmission over four-wire connection, the direction separation unit 41 operates in the space-division method. They thereby differs from the direction of separation unit for the two-wire connection to the interface in that here is always a continuous data stream occurs.

The codec contained in the conversion unit 35 and filters, which perform the analog / digital and digital / analog conversion of voice signals, are on the analog side to the microphone and earpiece of the speech circuit 20 and on the digital side of the 10-bit channel connected. The central unit 37 provides for the operation of the code and for reading in and reading out the 8-bit PCM words to and from the 10-bit data bus 39 (FIG. 4) required clocks are available: the bit clock TB, the Konverterakt TK and the word clock TW.

The conversion unit 35 also has control inputs »Converters a« CE and "converter of" CA. Activation and deactivation of the conversion unit 35 is required to reduce on-hook handset power consumption, so that a sufficient ringing current is available, and also in the case of data transmission via the main channel.

35 also read and write pulses are generated for the codec of the conversion unit. These two pulses provide the correct time writing or reading of the 8-bit PCM word from or into the 10-bit data stream. The interface line L is switched to active each present at the interface line DE 10-bit word during the first 8 bit clock.

The data in the outgoing direction, the 8-bit PCM words are in the first 8 bit time periods of each word in the previous 10-bit data bus, that is, the interface units DA appears. The light coming from the central unit 37 write command marks the location to be inserted 8-bit PCM words in the previous PCM channel. The interface line S has been activated during the first 8-bit clock periods each 10-bit word on the interface line DA.

At the interface line AE, which leads to the matching circuit or interface means 33 of the speech circuit 20, is the next signal in analog form with a defined level is available. At the interface line AA, which comes from the interface device 33, is the continuous signal in analog form with defined level available.

The D / A and A / D conversion in the conversion unit 35 is based on the A-law CCITT Recommendation G 711. The transmission characteristics in accordance with the CCITT recommendation G 712th

The central unit 37 includes a synchronization means for recovering the frame clock from the coming from the direction of separation unit 41 bit clock. It also includes a controller for multiplexing for the fade-in and reading information into and out of the main channel HKA and the additional channels ZKS, ZKD in and out of the 10-bit data bus 39. It provides the necessary write and read clocks to the codec and has means for adapting the signaling between the circuit parts of the basic equipment - hook switch 25, selector 27, number display 29 and Tonrufgenerator 31 - and the additional channel ZKS, specifically including the signal conditioning. The mentioned circuit parts 25, 27, 29, 31 are connected via a respective interface device or matching circuit 61, 63, 65 and 67 to the central unit 37th

In the event that the terminal 1 is provided with an auxiliary device, the bit clock, word clock and the frame clock from the central unit 37 by respective conduits TB, TW and TR interface I of the auxiliary device 3, 7 are provided. Two other signals on the interface lines FR and AK govern the priority between the telephone device 2 and the attachment 3, 7. In the outgoing direction are compared with those transmitted signaling mark the telephone device of the accessory principle priority, a transfer started the Additional Facility is however in any case to end out. The central unit 37 controls all timing sequences between the data bus 39 (interface IV), the conversion unit 35 (interface VI), the signaling means of the telephone set 2 (interface 111) and the auxiliary device 3 or 7 (port I).

In the central unit 37, a synchronizing word of 8 bit length is selected by means of the next bit clock TB from every ninth bit of the next data DE. In the outgoing direction, the synchronization word is the ninth bit of the first eight word periods each frame clock period in the previous data stream DA appears (see. Also Fig. 3).

During the assignment phase of a connection synchronization is supported in that, a synchronization supporting bit patterns appears in the remaining bits of the continuous data stream, which are not taken for the sync to complete. The insertion is interrupted as soon as the assignment request has been detected. During the synchronizing time and the incoming data stream is provided with a synchronization pattern supporting. This pattern is intended to speed up synchronization.

The synchronization is considered verified if the synchronizing word is detected twice in a row. If the synchronizing contrary shall be recognized twice, so the synchronization again is initiated. After you synchronize the frame timing TR and the derived word clock TW is provided by the central unit 37 next to the bit clock TB. Here, the bit clock is in continuous form fert LOVED.

Bit clock, Worttakt- and frame clock period begin simultaneously. A frame clock period is 32 word periods and 320 bit clock periods long.

After synchronization backup is continually monitored, whether contained in the header field of a frame period of the code characters for telephony in the data stream coming DE. If it is recognized along with the header for telephony in the drawing area, the availability prompt characters, so the insertion of the synchronization supporting bit pattern is first suspended in the continuous data stream, and then checks the state of the hook switch continuously. So every change of the hook switch of "laid" is from hibernation starting to "lifted" in the form of the busy label and any change of the hook switch of "lifted" after "placed" in the form of the trigger character in the character field of a frame clock period appears in the continuous data stream. Here, the header contains the code for telephony. The seventh bit of the header field is used to mark the field detection: "0" for control characters, "1 for a symbol of an internationally standardized alphabet (IA # 5.).

In order to control the code conversion unit 35, a read pulse L, is communicated by means of which the codec when a respective 8-bit PCM word on data bus 39 is available, or generates a write pulse S, through which communicated to the codec when each an 8-bit word to be displayed in the data. 39

The call reception occurs by when along with the header for telephony in the drawing field of a frame clock period the sign for call appearance in the data stream coming DE is detected, a memory is set at an output R for pager. If it is detected in the same way the sign of ring trip, so the memory is reset.

The number display 29 is controlled as follows. If it is recognized along with the header for telephony in the drawing field of a frame clock period the internationally standardized mark next data stream DE, the last four bits are 29 provided in parallel form along with a readout pulse (strobe) on the control lines DD of the display device.

Selecting is performed as follows. By means of the keys of the selector 27 is controlled via the four interface lines DT, the central unit 37, so that there incoming key code characters are converted into corresponding Binärcodezeichen. The Binärcodezeichen, along with the characters for "telephony" in the header field, appears in the continuous data stream in the fourth to seventh bit of the character field of a frame clock period. The first three bits of the character array, the bit sequence "110" is in this case assigned.

Basically a character assurance is performed by parity check with confirmation in signaling. With increased demand on the characters in the fuse box of each frame clock period, an error detection code characters are displayed in the continuous data stream. This code character is then checked and confirmed the receiving end.

At the interface with the option 3 or 7 are provided (lines TB, TW and TR) as already mentioned, the bit clock, word clock and the frame clock. To secure the priority the interface line FR is made passive when an arriving from afar by the hook switch 25, voucher or trigger character or coming from the selector 27 selection signals for transmission over the data bus 39 is available. The character transmission is delayed as long as the interface line AK has been activated by the attachment ago. In this way it is ensured that the transmission of a possibly already begun by the accessory character is completed.

The interface cable FR also serves to inform the respective attachment 3 or 7 terminal equipment on the operating state of the subscriber. They may be connected only active when synchronization is present and an occupancy prompt character has been received.

The apparent from Figures 6 and 7 subscriber line circuit 15 - also referred to as subscriber circuit - is the teinehmerindividuelle link between subscriber, ie, subscriber terminal 1 and -Anschlußleitung 11, Other facilities of the exchange - as the controller, the switch fabric, etc. (not shown in the drawing) - and the ancillary service facility 17. the individual circuit parts, which have a similar structure and similar functions as the corresponding parts of the terminal 1, with corresponding to provided a hundreds-digit supplemented numerals. These are essentially a central unit 137, a direction-separating unit 141 and a power supply unit 143 which also here by a serial data bus 139 by control lines 147, by on / off lines 149 and by priority lines 151 (see. FIG. 6) with each other are connected.

The basic version of the 16 line circuit 15 is designed so that it can be connected via a very small number of connections to the exchange and to the ancillary service facility 17th This simplification is achieved, inter alia by the fact that the clock of the exchange is used as a reference or system clock, and that the serial 10-bit data bus is used.

The power supply unit 143 may be (shown in the drawing) or a four-wire connector designed for a two-wire connection. It contains exchanger for coupling of the supply current in the subscriber line 11, wherein in the first case the current in the a- and b-wire and in the last case in the C-, D-, E- and F-wire is coupled.

The power supply unit is also provided with an occupant detection circuit in the form of a bit stream detector (in four-wire mode only in incoming direction), which responds when the subscriber is busy. The line status is indicated via a control line.

The 11 coupled into the cores of the lead current is set by a series regulator to a certain constant value. The the occupancy state on lead 11 be monitored and the transmission parallel bit stream detector has the same structure as the bit stream detector of the subscriber-side power supply unit 41st

It consists of a receiver with high-impedance input and threshold. A determined occupancy status (7 Fig.) Is an interface line BK displayed.

With the Einkoppelübertrager the required electrical isolation and level adaptation between the connection circuit 15 and the connection line 11 is performed. Within the connection circuit 15, the transmission performed asymmetrically (see FIG. Interface line g in FIG. 7).

The line circuit 15 and all subsequent devices are protected from possibly occurring on lead 11 surges through protective devices in the power supply unit 143rd

The power supply unit for a four-wire_-Terminal differs from the above-described in that here the current through a respective Einkoppelübertrager in the C, D and E, F veins is coupled, and that the bit stream detector monitors the bit stream to the e-f and veins ,

The direction of separation unit 141 corresponds to the terminal 1. It may be carried out either for a two-wire connection, and include a separation device which operates according to a time or frequency division multiplex method, or by a DC location process, but it can also be provided for a four-wire connection ,

The direction of separation unit 141 includes line driver and receiver. In it, the line encoding is performed. The required bit clock is in the outgoing direction from the clock of the exchange (so-called. Master clock) won and is also the central unit 137 is available.

From the subscriber-side direction separation unit 41, the unit 141 is different only in that here the line coder is turned off in sleep mode and can be switched from the occupancy detector in the power supply unit 143, from the central office or from the ancillary service facility 17 ago. To this end, three interface lines BK, BGV and BGZ are present, leading to a power source to be described later (Fig. 7). In order for the propagation delay on the subscriber line 11 has no effect on the clock allocation, in the steady state, a phase adjustment is performed.

Since the central unit 137 as mentioned clocked by the exchange, the official page of the digital subscriber line operates as a so-called. "Master" and the subscriber side as so-called. "Slave". By making a block 150 in the drawing elements of the exchange - as the controller and the switch fabric - indicated, which are supplied via a control line TS with the system clock (Fig. 6).

The central unit 137 comprises means for generating the synchronous pattern for detecting synchronization and Mulitplexbildung for the fade-in and reading information from the main and auxiliary channel in or out of the 10-bit data bus. The main channel is permanently assigned to the switching device, the additional channel for data feast of ancillary service facility 17th The additional channel for signaling ZKS in coming direction is conducted depending on the header of a signaling word toward central office or toward ancillary service facility 17th The data flow is thus clearly controlled. At the interface XII for direction separation unit 141 is transferred to the 10-bit channel. At the interface XIV to the switching center 150, only the main channel and its associated signaling is transmitted and at the interface XV for ancillary service facility of the 10-bit bus is again guided to. The interfaces XIV and XV are operated with the system clock of 2048 kHz.

For the signaling in the outgoing direction, the central unit 137 also controls the priority between switch 150 and ancillary service facility 17, and always in favor of telephony. The central unit 137 controls all timing between the data bus 139 (interface XIII), the switching device (interface XIV) and the ancillary service facility (interface XV).

The system clock, word clock and the frame clock standing on lines TS, TW and TR interface XIV available. The bit clock (80 kHz) and all write and read clocks necessary for multiplexing and Zeitlagenumordnung be derived from this clock. Bit clock, Worttakt- and frame clock period begin simultaneously.

The Sychronisiermuster is generated in the central unit 137, by using the fixed predetermined synchronization word appears in the ninth bit of the first 8 word clock periods each frame clock period in the previous data stream DA. In the reverse direction will be selected from each of the ninth bit of the next data DE that back sent from the subscriber terminal 1 sync.

In the remaining bits of the continuous data stream which are not taken for the sync to complete, a synchronization bit pattern supportive appears. The insertion is interrupted as soon as synchronization is available. During the assignment phase also the incoming data stream DA is provided with a synchronization supporting pattern. This pattern is evaluated and used to speed up synchronization. The synchronization is considered verified if the synchronizing word is detected twice in a row. If the sync word is not detected twice in a row, so the synchronization again is initiated.

After recognizing the synchronization an occupancy PromptString appears in the continuous data stream in the drawing field of a frame clock period, together with the code for "telephony" in the header field of a synchronizing word.

The main channel on the interface line DE of the data bus 139 is assigned to the 8-bit channel of the switching device on the interface line HE. Conversely, the 8-bit channel of the switching device 150 is assigned to the interface line HA determine the main channel in the 10-bit channel at the interface line DA. Here, the logic state of the first 8 bits is transmitted every word clock period in the 10-bit channel in the first 8 bits of a corresponding word clock period of the 8-bit channel, and vice versa. The central unit 137 contains the necessary memory.

If it is detected at the interface line DE in the header field of a frame clock period, the code character for "telephony", the logic state of the 8 bits of the character field is transmitted in the second to ninth bit of an associated frame clock period of the signaling channel of the interface line SE. Here, the signaling state (logic 1) appears in the first bit. If the header field of telephony is not recognized, the logic state of the 16 bits of the header and character field in the second to seventeenth bits of an associated frame clock period of the data channel EN the ancillary service facility 17 is transmitted.

In the outgoing direction of the auxiliary channel for signaling according to the priority of either the switch 150 or the ancillary service facility is taken 17 to complete.

If at the interface line SA in the first bit of a frame clock period, the state recognized logic 1, so the state is the second to ninth bits in the character field of a frame clock period displayed in the 10-bit channel at the interface line DA, together with the code for " telephony "in the header field. Otherwise, the state of the second is transmitted to the interface line DA interface XV in the head and character field to seventeenth bits of the data channel.

The additional channel for data in the 10-bit channel at the interface line DE is permanently assigned to the data channel of the ancillary service facility at the interface XV. Conversely, the data channel of the ancillary service facility is laid on the line DA interface XV assigned the additional channel for data in 10-bit channel at the interface line DA. Here, the logic state of the tenth bits is transmitted every word clock period of 10-bit channel in the first bit of a word entprechenden clock period of the data channel of the ancillary service facility and vice versa.

When signaling in 10-bit channel a character assurance is performed by parity check with confirmation principle. With increased security requirements in the security field of each frame clock period, an error detection code are displayed in the continuous data stream. This code is then tested and confirmed the receiving end.

Once the logic state 1 is detected on the line SA interface XIV in the first bit of a frame clock period, the line FR at the interface XV remains switched passively until the character made available is displayed in the 10-bit channel. If the interface cable AK has been activated, the character transmission will be delayed accordingly. In this way it is ensured that the transmission of a possibly already begun by the ancillary service facility 17 her character is completed. The interface cable FR can only be made active when synchronization is available.

At the interface XV are next to the line TB for the bit clock lines TRE and TRS for the frame timing in receive and transmit direction and lines TWE and TWS for the word clock in reception or in the transmission available.

To power the local loop is a central constant current source 155 which can be switched on or off via lines BK, BGZ and "off" respectively. The current supplied by its constant current is injected into the power supply unit 143 in the lead 11th

Details of the auxiliary device to the subscriber-side terminal apparatus 1 are shown in Fig. 8. There are two different types of them: Extras 3, 3A for data transmission via the main channel and auxiliary equipment 7, 7A for data transmission via the auxiliary channel (see also Fig. 1.). With the additional devices 3, 3A, it refers mainly to data transmission equipment with V- or X interfaces according to CCITT recommendations. The additional equipment 7, 7A, however, can be very diverse nature, such as Bildschirmtext-, telex, fax machines, etc.

The auxiliary devices 3, 3A, 7 and 7A are turned on in each case via interface devices 157, 159, 161 and 163 to the terminal device the first contains the interface, as mentioned above, the data bus 39, control lines 47, the lines 49 for turning on / off and the terminal equipment 1 and the wires 51 for securing the priority.

For the signaling in the outgoing direction, the priority of the terminal 1 is grungsätzlich specified. If more than one additional device 3, 3A or 7, 7A are present, the priority between the respective auxiliary devices is secured by lines 165 and 167th

The interfaces 161 and 163 for data transmission via the auxiliary channel includes means for showing and reading assignment mark and trigger mark in continuous or from incoming direction into or out of the 10-bit data bus. For continuous availability, the power supply unit 43 is turned on in the terminal. 1 In addition, facilities for fading and reading to and from the data bus 39 are present, so that the additional channel for data than transparent 8-kbit / s channel including clock is available.

To superimpose or reading required write and read clocks are derived from one bit, frame clock and word clock.

The devices 169 and 171 with which the interface devices 161 and 163 access the interface lines 39, 47, 49 and 51, are shown in dashed lines in the drawing. The same applies to the access devices 173 and 175 of the interface circuits 157 and 159th

In the event that for reasons of security priority in favor of the terminal apparatus 1, the signal transmission must be delayed corresponding intermediate memories are provided. The interface circuits 161, 163 also include means (code converters, memory, etc.) to adapt the data channel of each accessory to the auxiliary channel for data, which is from the general part of the interface device forth in transparent form. In addition, here takes the final adjustment to the in the attachment 7, 7A instead of conventional occupancy.

The interface circuits 157, 159 for data transmission over the main channel comprise means (code converter, memory, etc.) for adaptation of the data channel of the auxiliary device to the 10-bit data bus. The required write and read clocks are derived from the bit and the word clock.

With documents of the main channel HKA by data services via the accessory 3 35 of the terminal 1 is switched off via the respective interface circuit of the codec in the conversion unit. The attachment is only released when synchronization is available.

The construction of the central unit 37 and the conversion unit 35 of the subscriber side terminal device 1 are shown in Fig. 9. The central unit 37 essentially comprises a transmitter 171, a controller 173, a clock supply 175 and a receiver 177, which are connected by respective conduits to one another. The transmitter 171 includes a transmitter memory 179, a synchronizing circuit 181 and a Signalcodierschaltung 183. The receiver 177 includes a reception memory 185, a synchronizing circuit 187 and a signal decoding circuit 189 on.

The central unit connected to the other circuit components of the terminal apparatus 1 interface lines correspond to the interface lines of FIG. 5, as indicated by the dash-dot indicated interfaces I, 111, IV and VI. At the interface between VI of the central unit 37 and the conversion unit 35, the lines L for the transfer of read pulses and S for the transmission of write pulses are combined to a common line LIS.

Via the interface I, the central unit 37 can be connected to the auxiliary devices 3, 7, and the auxiliary support 53 via the interface 111 is connected to the telephone set 2 via the interface IV it is connected to the direction-separating unit 41 and the line " from "used to turn off the Stromversorgungseinheit43.

The conversion unit 35 includes a voice band limiting filter 191, a D / A and A / D conversion by leading codec 193 and a memory 195 in which the digitized voice signals are latched in outgoing and incoming direction.

From Fig. 10, the structure of the central unit 137 of the exchange-end subscriber line circuit 15 is visible. It comprises a receiver 197, a controller 199, a clock supply 201 and a transmitter 203, which are connected by suitable lines to each other.

The receiver 197 includes a reception memory 205, a transmission buffer 207, a signal decoding circuit 209, a synchronizing circuit 211 and a signal decoding circuit 213th

The transmitter 203 includes a transmission buffer 207, a reception memory 217, a Signalcodierschaltung 219, a synchronizing circuit 221 and a signal decoding circuit 223rd

The interface line connecting the central unit 137 with the other circuit parts of the line circuit 15, are the same as in Fig. 7, and there have been already set forth in part. This is indicated by the dash-dot indicated interfaces XIII, XIV and XV. The interface XIII, the central unit 137 is connected to the direction-separating unit 141st Via the interface XIV it is connected to the means 150 of the central office and the interface XV it can be connected to the ancillary service facility 17, the connection between the main channel in the case of data transmission as well as the auxiliary channel for data transmission with the different data networks or z. B manufactures. with videotext headquarters. A line labeled "off" used to turn off the power source 155th

The interfaces to the XI to XV of 7 and 10 provided lines now appear related. At the interface XI are at the illustrated in the drawing symmetrical two-wire connection, the tip and ring wires of the subscriber line 11. In the case of a symmetrical four-wire connection are here the c-, d-, e- and f- cores available.

At the interface XII is a line in a two-wire connection g for asymmetrical transmission in line code, in the case of the four-wire connection, the line i for incoming data, wired in line code and a line j for continuous data, unbalanced, provided in the line code. Coming for assignment In addition, a line and a line BK SV for the constant power supply.

At the interface XIII lines are available: TS for the system clock, TB of the bit clock, TW for the word clock, DE for incoming data in binary code and DA for continuous data in binary code. The interface XIV has the following lines to: TS, TW and TR for the system, word or frame timing, SE for signaling coming, SA for signaling extent, HE coming for the main channel, HA for main channel going and BGV for documents from the switching device 150 from.

At the interface XV following lines are provided: BGZ for documents from the ancillary service facility 17 from DA for continuous data in binary code, DE for incoming data in binary code, FR for release (for signaling of the ancillary service facility), AK to active-switching (for signaling of the ancillary service facility), TB of the bit clock, TWS for the word clock in the transmission direction, TBS for the bit clock in the transmission direction, TWE for the word clock in the receive direction, TRS for the frame clock in the transmit direction and TRE for the frame clock in the receive direction.

Both the central unit 37 and the central unit 137 are implemented as hardware circuits that can be made from commercially available active and passive components, are expediently designed as an integrated circuit.

The auxiliary channel ZKD (see. FIG. 1) can be used either for the transmission of a data service (eg. As screen text, teletex or telefax) at a time, but with different services can be transmitted at different times, but it is also possible that compounds for the different services are simultaneously produced, wherein each service a fixed sub-frame is assigned.

In SIGNALLING and synchronizing channel ZKS can next to the signaling for the main channel HKA and the additional data channel ZKD more signals between a subscriber and a central device, such. As an alarm center, to be replaced.

The channelization in message delivery can be made as follows: a main channel with 64 kbit / s, a synchronization channel with 2 kbit / s and a Zusatzdaten- and signaling channel with 14 kbit / s, the additional data and the signaling data equally as information packets, as appropriate, several services are simultaneously transmitted.

By dividing the terminal 1 and the connection circuit 15 in several functional units and through the clear definition of interfaces, a modular construction of the messaging system of the invention is made possible. Specifically, the system can be adapted to various directional separation procedure by which is arranged on a printed circuit board direction separation unit 41 and 141 replaced. The separation of the basic design of the terminal 1 of the via the interface I (Fig. 5 and Fig. 6) can be connected by simple plug connections Komfortausstattung 53, additional device 3 for data transmission via the main channel and auxiliary device 7 for data transmission via the auxiliary channel allows for remote powering of the telephone set in the basic design on the outside line. In contrast, the options and the comfort features are ortsgepeist.

During a still expected prolonged transitional period which aspired to be fully digitized telephone network will not be present. digital subscriber line It is therefore possible to operate in conjunction with analogue local exchanges. In such cases, between the respective subscriber line circuit 15 and the analog switch must be inserted a suitable adjustment facility that will cater for a D / A and A / D conversion and signaling conversion.