Message network for the transmission of digital telegrams with an address consisting of routing words

(24) Running day

Patent Office (62) National application number (86) International filing day ib) (2D 7604619-2 (11) Publication number

H 04 L 11/20

424 798

KB 3-A4 according to SIS 61 30 13 DB 34975 ALLF13B8I109 (86) Filing date for European patent application (30)

75-04-25 CH 5346/75

Application received as:

® Swedish patent application □ completed international patent application with number □ converted European patent application with number (71) Applicant: HASLER AG, BERN, CH (72) Inventor: E Hafner, Wohlen and H Mey, Kehrsatz (74) 0mbud: Ferkinghoff (54) ) Name: Switching device for a transmission site in a digital telex network

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The invention relates to a switching device for a transfer site in a digital telex network for transmitting code-addressed information packets from the input memories of the forming sites to their output memories.

- wherein the telex network comprises several switching points which are connected to each other and to subscriber points connected to them by lines, which are referred to as road sections,

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- where the characteristic of the road sections belongs to each road section, a word of guidance,

- each address packet address includes a forwarding information which is compiled by guidance words in such a way that the number and order of the guidance words correspond to the number and order of the road sections which must be successively followed by the information packet in question,

- after which each input memory is connected to an oncoming road section and each output memory is connected to an outgoing road section,

- and wherein the passing of each information packet occurs only at the output memory connected to the outgoing route, to which belongs the guidance word, which is equal to the guidance word, contained in the guidance information for the information packet at a predetermined location.

Digital news dissemination and editing has gained wide popularity today. Thus, there are e.g. telex networks, digitally working telex centers and memory switching devices for teleprinter traffic. Furthermore, digitally working data transmission networks exist in telephone lines, which are fixedly connected as rental or standing lines.

The German publication specification 2 441 099 discloses a combined telephone and telegraphy network, which consists of a step communication network connected via digital channels. The information runs successively in the form of address-encoded information runs through the formation step, whereby in each step the correct selector sign for the step in question is read, which forms part of the address. The read selector sign then indicates via which output line the information block should leave the switching step.

The head of the information block shows for the addresses, as many selector characters as the number of mediation 7604619-2 stays, which must be completed. Thus, each switching step to be followed is a constant length selector sign. Furthermore, the head has one or two control characters, which serve as counters and which indicate the relevant address counter device, which selector character that must be read.

Thus, the length of the information block heads varies according to the number of mediation steps, which the information blocks must go through but remain constant for the entire life of the block.

Thus, the head of the information block is relatively rigid and is particularly suitable when a large amount of information is to be transmitted simultaneously. For short information blocks, the head would be too long and the relationship between useful information and head length would be very unfavorable.

When used for telephony, each eight-byte information character occupies a PCM sensor value, so that at a maximum of 256 eight-byte control and information characters for a single information block, a significant number of sensor values ​​can be simultaneously implemented. This requires a significant measure in the end devices for the preparation and processing of information packets. are recorded jointly. By means of input, output and intermediate memory in the pre-processing stage, the measures for the memories are multiplied, which are necessary in the formed telephone and count graph networks;

Thus, the German publication disclosure 2 441 099 describes essentially a memory transmission network for telegraphy and teleprinting facilities, which can also be utilized for telephony applications through special fast communication steps and special priority signs in the information block heads.

An object of the invention is to provide a general, digital information network for short, address-coded

7604619-2 telegrams, which operate without routed wires, to which at any time, regardless of the load's load condition, any participant can send at least one short telegram and which allows duplex connections, coupling, control and storage measures for guidance to the address-coded telegrams to be sent; shall be kept as small as possible.

In order to achieve this, the invention is characterized

- by a multiplexer connected on the input side to all input memories and on the output side to a channel to which it multiplexed transmits the information packet contained in the input memories together with the associated guidance information,

- of intermediate memories, all of which are connected to the channel at the input side and connected to one of the output memories via an associated transmission connection,

- of memory and comparison links, which are separately assigned to the transmission links for recording a guidance word and for comparing this guidance word with the guidance word present at said predetermined location of the guidance information in the currently available information packet,

- where a transfer link is arranged to transmit an information packet, only in the associated output memory, when said comparison has shown that the two said guidance words are equal.

By this means a multiplexer means a switching device with multiple inputs and an output, which always connects only one input to the output.

The information network conveniently operates msd a large number of short, time-multiplexed telegrams.

The goal of telegrams cannot be read directly from guidance addresses, but is evident from the order-correct successive deletion of guidance words that belong to the

7604619-2 wires through which the telegram is to pass, The coupling and control measures for the connection points are limited to simple comparison couplings, which always compare only the guidance word at the address location with the guidance word stored in the fixed value memory, which is appropriate for the switching point in question. Conveniently, the telegram is transmitted in accordance with the guidance word in the fixed value memory and the guidance word at the address for the address without transmitting this guidance word to the output memory. The memory need is therefore small and limited to small buffer memories for a few telegrams.

In addition to the simplicity of the connections, the information network described has the following advantages. There are no connected connections. Therefore, wires are charged, except when telegrams are sent and call breaks do not load wires. On their way through the network, the telegrams are guided by short instructions at the switching point. Therefore, the switching points do not require any devices for storing existing connections, destination addresses, etc. Furthermore, the organization of the information flow becomes simple. The guidance words must be unambiguous and distinguishable only for a single intermediary. Otherwise, its construction is freely selectable.

The invention will be explained in more detail in the following with reference to the accompanying drawings, in which Fig. 1 symbolically represents an information network and Fig. 2 illustrates the structure of the telegrams used; Fig. 3 shows a block diagram for a forming site and Fig. 4 shows a detailed diagram. for an input circuit and the multiplexer having a variant of the switching point of Fig. 3, and Fig. 5 shows a detailed diagram of an output circuit of the switching point of Fig. 4.

Fig. 1 is a symbolic representation of a digital information network with nine equivalently formed switching points 101 - 109. Between the forming points are transmission lines, which are illustrated by lines and are partly denoted by the numbers 12, 13, 14, 15, 16, 17, 10, 19. associated with at least one of the other connection sites. Most of the lines have been designed double, namely separate for the way back and forth, and in the drawing they are indicated by arrows.

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The switching point 107 is connected to the two switching points 101 and 108 with only a single wire. Between the switching sites 102 and 105, two dual wires exist and the switching station 109 is connected only to the switching point 108. Some or possibly all switching points have a plurality of local participants, though only the two participants A and B are displayed at switching points 101 and 104.

To each output line leaving the switching point, a depth of illumination in the form of a digital bit series is taken from the switching point. This bit series can be selected according to any code, and has different lengths. Here, guidance is symbolized by the lowercase letters a, b, c, etc.

The different output lines in a switching point are assigned different non-guide words, so that they are unambiguously and distinguishable in that switching point. Thus, the ordering words in the mediation site 105 carry the terms o, d, c, n and u with conditional distribution. The guidance words at the other mediation sites are equal to or different the guidance words at the mediation site 105. In all cases, however, the separability is given within each mediation site, ie. each letter appears at its height once at a mediation site.

The flow of information through the described lines is accomplished by serial transmission of a number of short telegrams. Each telegram is address-coded, each address being formed by sequencing of the guidance words, which in the correct order are passed to the lines through which the telegrams are to pass.

If there is a voice connection between participants A and B, alternating telegrams are transmitted both by A and B. These telegrams must pass at least four switching points but can also travel a longer route, if the road address so requires. Possible paths for A and B are

A ---> 101 --- 9 102 --- 9103 ---> 104 --- 9 B

<img file="SE424798B_D0001.tif" />

<img file="SE424798B_D0002.tif" />

<img file="SE424798B_D0003.tif" />

etc

7604619-2 the associated addresses read:

p / d / g / bp / b / c / bp / c / c / br / f / c / bp / d / h / d / b osu.

Since the path of the telegram is practically freely selectable, the path of the telegram from A to B must not be consistent with the path to B from A. As a special case, however, in principle the same route can be taken in both directions. In addition, the two lines are assigned to all the connection line pairs in the limiting connection places always identical guidance words (example: the connection line between the switching points 104, 108 always the guidance word d). for guidance words.

Each connection point has further been described in the following as comparison connections leading the telegrams in correspondence with their address to the intended output line. In order for the comparison connections to be constructed in the simplest possible way and each switching point can easily determine immediately the guidance word for this intended, one of its output lines, this is for each switching point either at the beginning or at the end of the whole address, whereby in the following it is assumed that said guidance word is the first guidance word for the address. This means that the address of each telegram must be changed at the passage of each connection point in such a way that the next connection site or its comparison connections find the guide word for the same destination at the right place. One possibility for this change of address at each switching point is the cyclic exchange of the guidance word for the entire address. Another simpler way is to see therein that the intended place of employment for the be7604619-2 and read by this agency place is taken out of the total address and eliminated. As a result, the telegram address is shortened from a through-switched switching location to a through-switched switching location each time with a guide word.

Fig. 2 illustrates this process. By way of example, a telegram is considered as participant A on the road via the switching points 101, 102, 10 ^, 104 is sent to participant B. The telegram length amounts to several times the block length L, which itself consists of 8 bits.

The telegram length is variable and changes along the route through the information network. The telegram comprises three areas: the signaling area Sig, the address area and the information area. The signaling area comprises 8 bits and a block length L. The address p / d / g / b, which consists of the guidance words for the lines to be followed, is arranged in the correct order. The length of the different guidance words varies with the number of bits required. In FIG. 2 it has been assumed that the guidance words have the following lengths:

Guidance word p: 4 bits guidance word d: 7 bits guidance word g: 5 bits guidance word b: 8 bits

The address area then fills three block lengths in the example according to Fig. 2. The information area further comprises

2.5 block lengths L. In order for the telegram to receive a length of 7 L, four additional filling bits FB, which have no information content, are switched on.

During the passage of the information network on the prescribed route, the address of the telegram at each switching point is incrementally shortened, thereby always eliminating the lowest front guidance word. The residual address and information area are then shifted in such a way that again the front guidance word is connected to the signaling area. They freed

The 7604619-2 rear positions are then filled with filling pieces. In Figure 2 this process is illustrated schematically by arrows. Thereafter, the address and information area are displaced to the left, while the singalization area remains the constant word constant throughout the telegram. The address is abbreviated as follows:

Address at the place of connection:

101 : p / d / g / b

102 : d / g / b

103 : g / b

104 : b

Contains the last block A only filler bits FB, disconnects it and eliminates it.

In Fig. 3, the switching location 104 is shown schematically. The switching point 104 is connected to the adjacent switching points 103, 105, 108. via the three connecting line pairs. The arriving lines have been designated 14, 15, 16 and the outgoing lines with 17, 18, and 19.

The switching location 104 has input slider register 1 and

2, a time multiplexer unit 4 and output slider register 5 and

6, Frame synchronizers 3 determine, for each input line 14, 15, 16, the frame number y marked by an arrow and control with it the associated shooting registers 1. A comparison connection 7 with a fixed value memory is stored in each output shooting register 5 in which it is stored. output line 17, 18, 19 hearing the guidance word in, a, d.

Via the input lines 14, 15, 16, telegrams occur independently of each other at irregular distances from the neighboring switching points 103, 105, 108. The telegrams run at the transmission register 1 bit by bit in the shooting register 1. The frame synchronizers 3 detect and regenerate for each input the frame rate of the telegrams and, when a telegram initially occurs at the end of a slider register 1, as soon as it is, the entire telegram is overwritten in parallel to the associated register 2, thereby releasing said register new telegram.

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The time multiplexer unit 4 is a symbolically rotating switch designed electronic unit with several inputs connected to the registers 2 and an output connected to a collection line 10, which unit 4 connects the register 2 in cyclic series to the collection line 10. If a shooting register 2 contains a telegram, this is offset. at the rate X in line 10, as soon as this shooting register 2 is requested. The rate x illustrated by an arrow x is faster than the rate y and the call to the shooting register 2 occurs so quickly that no congestion can occur in the registers 1 and 2.

In line 10, the various telegrams run time multiplexed and in series. Each telegram simultaneously reaches the inputs of all output slider registers 5 and runs bit by bit into these registers.

The comparison links 7 connected to the registers compared the first guidance word in the telegram's address with the guidance word stored in its fixed value memory. Since each output line 17, 18, 19 has been assigned its own guidance word that differs from the other output lines from this switching location i, a, d, only at one output can a match be determined between the guidance word stored in the fixed value memory and the first guidance word in the telegram. However, at all other outputs there is no compliance.

If there is no conformity, the telegram examined is overwritten with the next telegram and is wiped out in this way. At the output at which correspondence was established between the telegram guidance word and the guide word for the fixed value memory, the entire telegram is transmitted to the detected routing path in the detected path. This process has been suggested in FIG. 3 by means of an arrow between the comparison coupling 7 and the register 5 and this has already been explained in connection with Fig. 2.

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The shooting register 6 has a certain recording capacity. This is necessary for the telegrams to be intermittently stored. Through the intermediate storage, the equalization between the faster rate X and the slower transmission rate y is realized. The value of the recording capacity depends on the load on the line and can be determined by the methods according to the traffic theory.

The hitherto described part of the switching point allows for easy guidance of the telegrams arriving from one of the output lines 17, 18 or 19.

In the following, the local network belonging to the switching location 104 will be described.

Of the local participants at the switching station 104, in Fig. 3, only the participants B, C, D and E. are shown. and 13, as well as the structural units 1 ', 2' and 5 ', 6', and 7 ', all of which are identical to those already described, corresponding to the structural units 1, 2, 5, 6 and 7 and which have also been already described.

The connector units 20 have been extensively described in Schuizian patent 550 521. They fulfill the following functions. They all receive telegrams sent in line 11 and they examine each telegram in that regard if it is intended for the associated participant. They extract the telegram intended for this participant from the traffic stream. They forward all other telegrams. They provide a time space for sending their own telegrams. They have the address of the connection in question stored and provide each address with their own telegram.

The lines 11, 12, 10 and 13 together with the construction units located therebetween form a ring system in which the cloth frames are transmitted exclusively clockwise. In all these lines, all local traffic is wound down.

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Calls two participants, e.g. participants B and D, with each other, telegrams the said wires clockwise until they reach the participants' connection unit 20. Thus, the telegrams from the participant D thus reach participant B in the shortest way via the line 11 and the participant connection unit from the participant unit C. The telegrams from participant B, however, gradually pass through wires 12, 10, 13 and 11 as well as the units interconnected, before reaching the participant connection unit from participant D and being withdrawn from the traffic flow.

In the last described way, the telegrams pass through the construction units 1 'and 2'. They are called from here as in the previously described telegrams through the multiplexer unit 4 and are routed in the multiplex line 10. Via address comparison in the construction units 5 'and 7', the telegrams reach the sliding register 6 'and thus renew the local network.

Thus, the multiplex unit 4 joins all of the conduit 10 via the units 1 and 1¹ arriving telegrams regardless of their addresses. Similarly, all units 5 and 7 and 5 'and 7' examine all telegrams. In this way, all directional possibilities can be treated in a uniform manner. The directional options consist of: transfer teagrams from one nearby intermediary to another nearby intermediary; local telegrams from one local participant to another local participant; outgoing telegrams from the local participants to a nearby intermediary; arriving telegrams from the nearby exchange office to the local participants.

The exchange or expansion of the information network is possible through simple steps:

- new participants are connected via their additional participant connection unit 20 to line 11.

- an additional local network can be provided by connecting an additional ring system with its own guidance word to the multiplex line via additional units 1 ', 2', 6 'and 7'

- additional connection lines are connected by the addition of

7604619-2 new units 1, 2, 5, 6 and 7 and assignment of a guidance word to a permanent mediation office.

- When overloading the time multiplexer unit 4, there are opportunities for expansion therein that a part of the connection lines and / or the local ring system is re-summarized by means of an extra multiplexing unit 4, thereby forming a new switching location, which in the room is located close to the original switching point and may be connected via one or more connecting lines.

- Brand new switching points are inserted in the information network by connecting the necessary connection lines and assigning the necessary guidance words.

Figures 4 and 5 show a suitable, detailed illustration of the switching point 10 shown schematically in Figure 3; Figure 4 shows the input circuit of the input lines 14 and the multiplexer in the switching point and Figure 5 the output circuit of the output lines 18.

Via the arriving line 14, which is designed as a conventional PCM line, at the rate y, the continuous input register register 1 reaches a frame synchronization 3 arranges the bits to block L for each eight bits, as is known from the PCM technique. As a result, eight successive blocks, one block forming bits, always arrive at the shooting register. Via eight AND gates 51.1 - 51.8, the contents of the shooting register 1 are always read after eight bits in parallel in the lines 52.1 - 52.8, for which a control pulse is delivered via a control line 31 from the frame synchronization 3. Corresponding to the contents of the shooting register 1 The 52.1 - 52.8 signals are logically 1 or 0.

The section L is stored without distinction successively in a register 2, which is designed as an eight-bit parallel First-in-First-Out Memory Register (FIFO), whose capacity comprises two full telegrams of maximum length. At the same time, the significance of all blocks L. is tested. For this purpose, two gates 53 and 54 reproduce the bit combination of signaling and filling bits respectively. They thereby leave at the beginning of one

7604619-2 telegram (gate 53) or after passing through a telegram (gate 54) via wires 33 and 21, respectively. 34 always sends a signal to a calculator and control unit 35. This unit 35 further obtains via the control 31 the frame synchronization rate, so that by simple logical interconnection the beginning, length and end of the telegram can be determined.

If a telegram is completely enclosed in the First-in-First-Out memory register, the counter and control unit 35 sends via a line 36 a corresponding message to a control 37. This control 37 forms part of a time multiplexer corresponding to the time multiplexer 4 in FIG. 3, and via the lines 36 ', 36' ', 36' 'irregularly receives corresponding messages from the other input circuits of the lines 15, 16 and 12 not shown.

The control 37, in cyclic order, always emits only in the presence of a message to the corresponding line 36, 36 ', 36, 36 * * * control signals to the lines 38 and 39, 38' and 39 ', 38 respectively. 38 'and 39'.

The output of register 2 is connected to AND by gates 55.1 - 55.8 connected to lines 56.1 and 56.8 through line 38. The first control signal to line 38 opens in parallel all AND gates 55.1 - 55.8, whereby the bits in the first telegram block L are passed bit parallel from register 2 to lines 56.1 - 56.8. When gates 55.1 - 55.8 have been closed again, a signal in line 39, which is the forehand with register Z, pushes the contents of First-in-First-out register 2 one place, after which by opening gates 55.1 - 55.8 the second the telegram block arrives at lines 56.1 - 56.8. This process is repeated until the entire telegram in lines 56.1 - 56.8 has read. Thereafter, control 37 is coupled to the next input circuit 12 of the input line 12 and the associated control lines 38 ', 39', etc. not shown.

The conduits 56.1 - 56.8 together form the multiplex collection conduit 10 in Fig. 3, which is driven by eaves x and

7604619-2 occur in which bit parallel and block series sequentially occur telegrams ^ from all input lines 14, 12, 16, 15. As soon as a block L contains only filler bits, it is offset by forwarding signals in the counter and control unit 35, which signals are output in a conduit 40 connected to the register 2, within the first-in-first-out register 2 in such a way that it is finally obliterated and does not reach conduits 56.1 - 56.8.

Fig. 5 shows the output circuit belonging to the output line 18 from the switching point. To the multiplex conduit 10 formed by the eight parallel conduits 56.1 - 56.8, the following units are connected: eight AND gates 61.1 - 61.8, eight AND non gates 62.1 - 62.8, one gate 63 which reproduces the bit combination error signal and which is identical to the gate 53 in FIG. 4 and a gate 64 which reproduces the bit combination only fill bits and is identical to gate 54 of Fig. 4. Gate 63 is connected to controller 65, which via a line 66 controls all gates 61 and 62 and is additionally connected to a controller 67. The controller 67 receives additional signals from a gate 68, which reproduces the guidance word that belongs to the output circuit shown. Thus, the gate 68 corresponds to the fixed value memory in the comparison circuit 7 in FIG. 3 for the output line 18. The gate 68 has four inputs and reproduces the guidance word a.

The output circuit has two additional registers 5.1 and 5.2 for each of the eight bits corresponding to the output slider register 5 of Fig. 3. A slider register 6.1 for twelve bits and a First-in-First-out register 6.2 corresponds analogously to the output slider register 6 of Fig. 3. a parallel / serial transformer forming push register 75 and a control 74 for registers 6.2 and 75 complete the device.

Via the multiplex line 10 and the lines 56.1 - 56.8, all telegrams are routed to the gates 61, 62, 63 and 64. The gates 61.1 - 61.8 are generally open and the gates 62.1 - 62.8

76046 ί 9-2 blocked. As a result, all blocks L are successively inscribed and rewritten by the next block.

However, as soon as gate 63 registers the beginning of a telegram, which is characterized by the combination signaling, AND gates 61.1 - 61.8 are blocked via controller 65 and line 66, and at the same time AND gates 62.1 and 62.8 are opened. In this way, the second telegram block, which according to Fig. 2, always contains the guidance word to be read, is inscribed in register 5.2. At the same time, the first guide word for the telegram address is compared to the reproduction of this word by the gate 68. If the comparison becomes negative, no reaction will occur.

Thus, if the address comparison requirement is positive, the telegram address guidance word and the reproduction thus correspond, then a signal is generated via the output of gate 68. Hereby the controller 67 opens all AND gates 68.1 - 68.12 and the contents of register 5.1 and 5.2 are transmitted to the guidance word reproducing bits. push registry

6.1.

Controller 67, independently of the address comparison for the third telegram block, regenerates the original state of gates 61.1 - 61.8 and 62.1 - 62.8. Hereby, this third and all further blocks are returned to the register 5.1.

In positive address comparison, the control unit 67, in conjunction with the transfer of the register contents from register 5.1 and 5.2 - 6.1 via the line 69, delivers a 12-bit clock series, whereby the entire contents of the final register 6.1 are transmitted separately to the First-in-First-out register 6.2.

In the rhythm of the telegram blocks arriving via lines 56.1 - 56.8, the blocks are inserted in the slider register 6.1 and the serial transfer to the register

6.2. For this purpose, the control unit 67 always opens the AND gates 68.1 - 68.12 and in connection therewith emits an eight-bit clock series via the line 70 to the slider register 6.1.

This operation is interrupted as soon as either control 65 via line 66 announces the beginning of a new telegram or gate 64 a mere filler bit block.

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Control 74 controls the reading of telegrams from the First-in-First-Out register 6.2. For this purpose, the telegrams are transmitted blockwise in parallel to the shooting register 75 and then pushed with the rate y into the output conduit 18. When no telegram is present in the register 6.2, the control 74 ensures the transmission of only filler bit blocks.

The device described above has in particular the following advantages:

a) Addressing the telegram will be simple. The address consists of the successive erasure of guidance words, the type of these guidance words being largely free and identical from intermediary to intermediary and can be similar or different.

b) The traffic flow is clearly and simply organized. As a result, no collisions between different telegrams can occur. By means of the time multiplexing unit 4, a telegram arrangement is determined, which clearly clarifies sooner or later.

(c) In the intermediary, transit traffic and local traffic are to a high degree treated in the same way. Therefore, the transition is possible in a simple way between the two areas of this intermediary.

d) The expansion of the intermediary sites and the information network is very simple.

e) Each liaison liaison, the transit area and each local area at the intermediary sites operate at their own pace. This eliminates the synchronization of the entire network.

(f) In the intermediary location, only the guidance words for the outgoing lines or for the transition to the local area are stored. However, no information may be stored via existing connections.

g) Telegrams without information, which may arise e.g. during call breaks, is not broadcast and therefore does not burden the information network.

h) The number of different design groups in the intermediary is low, which is very important from an economic point of view.

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i) The control measures are minimal.

The embodiments of the switching sites described with reference to Fig. 3 and Figs. 4 and 5 can, for example, be designed in a different way than in the following very arranged in another way:

- The connection between the registers 2 and the collection line 10 by means of the time multiplexer units 4 does not proceed cyclically, but the registers 2 are connected in sequence with the collection line TO, with which order they have received a telegram.

- The transmission of the telegrams in line 10 can proceed bit-by-bit, in parallel or in mixed operation.

- Synchronization can be rigid throughout the information network.

- At a switching point, the number of arriving and departing connection lines may be different.

- The structure of the telegrams may be different. Thus, e.g. the order of the telegram areas address and information is exchanged with each other or the block length L can be selected differently.

- Instead of the address shift and the elimination of the last read guidance word, the read guidance words can be marked to characterize the associated guidance word in the next switching place.

- Furthermore, the characterization of the guidance word to be read can proceed with a binary number included in the telegram and always after the reading of a guidance word is increased by the number of bits in the read word.

- Participants A, B etc. is not connected via a local ring system to the switching point but directly, exactly as an outgoing transmission line,

- A participant connection unit can be assigned to several participants and thus act as a transformer.

- The local telegram traffic does not proceed via the multiplex line 10, but is developed via its own connection line between the lines 12 and 13.

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- The participant addresses do not exist in the participant connection unit 20 without being entirely in a central memory. In this case, each telegram intended for the local area examines this memory and extracts where the guidance e.g. in the form of a number, which means the additional participant connection units to be traversed.

- The participant addresses can be found in a connection unit 20 designed as a concentrator for several participants.

- If there are several parallel lines between two switching points, these lines may have identical guidance words, unless an additional device ensures that each telegram is distributed only on one of the parallel lines and the traffic flow is distributed evenly over all the lines.

- The periodic interim storage of the telegrams by means of buffer memory for equalizing irregular line loads may, instead of at the output lines, proceed at the input lines as well, by extending the shooting register 2 to a corresponding degree.

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