DE1267288B - Time division multiplex transmission system - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int CL:

H04j

German KL: 21 a4 - 49

Number: 1 267 288

File number: P 12 67 288.7-35

Filing date: March 19, 1965

Open date: May 2, 1968

The present invention relates to a time division multiplex transmission system, in which the fact is exploited that the occupancy time of a transmission channel in each of the two directions during a telephone conversation less than half of the total call duration is the ratio of the number of connections made to the number of calls required Increase frequency bandwidth.

In the so-called call interpolation systems (TASI) it is already known to utilize the non-occupancy time of the individual voice channels in order to connect a number η of voice lines to a transmission device which is greater than the number m of available transmission channels.

In such transmission systems, the voice lines are connected to the transmission channels (which can be of any type, but mostly Time division multiplex channels are) via a so-called TASI device, which is in the individual voice lines only assigns a transmission channel while it is being used. So the TASI facilities are completely independent of the multi-channel transmission system and are only used to connect the speech lines in the most expedient way to switch to the transmission channels. The cost of the TASI facility is therefore in addition to the costs of the transmission system fully in the system costs, so that the use of call interpolation systems so far only for very complex transmission paths, like submarine cables, was economical.

With the invention specified in claim 1, this disadvantage is avoided.

The system according to the invention therefore works on the same principle as the known call interpolation systems, however, using a pulse code modulation device in which the coding of the incoming from the individual voice lines Signals is interrupted if the line in question remains unoccupied. As a result is the maximum number of lines to be scanned in one work cycle in the vast majority of cases (over 999% o of the call duration) less than half the number of all connected to the facility Cables. So if the maximum number of scans that can be carried out in one cycle is set equal to half the number of all speech lines connected to the system there is no need to fear any noticeable deterioration in the transmission quality. In such a case it is the time required to complete a scan cycle is equal to half the time required Time division multiplex transmission system

Applicant:

Societä Italiana Telecomunicazioni
Siemens spa, Milan (Italy)

Representative:

Dr.-Ing. E. Sommerfeld and Dr. D. v. Bezold,

Patent Attorneys, 8000 Munich 23, Dunantstr. 6th

Named as inventor:

Dr.-Ing. Evangelo Lyghounis, Milan (Italy)

Claimed priority:

Italy March 24, 1964 (6546)

would be necessary if all connected lines were scanned in each cycle.

Since the clock frequency when scanning the voice lines is fixed at 8000 samples per second is, d. i.e., one scan takes 125 μβ each time, Obviously, when doing a smaller number of samples per cycle, one has one longer period of time is available for each sample, and the duration of each pulse that is over the transmission path to be transmitted can be selected larger than one from the operating state independent sampling of all connected lines during each cycle. On the other hand, the The bandwidth required for pulse transmission is inversely proportional to the pulse duration, results if the impulses are lengthened, there is a saving in terms of the bandwidth of the transmission path.

Since the lines scanned during a cycle are not necessarily the same as in previous cycle, additional information must of course also be transmitted that it is the receiving Remote station enables the coded information to be correctly transmitted to the connected outgoing Distribute lines. This information is to be referred to as "distribution information". To the

So transmission of this distribution information is at of the present invention transmit a number of additional pulses during each cycle that

809 574/134

is equal to the number of voice lines connected. The number of pulses in a cycle is therefore at a system with η lines, of which during

each cycle only ~ can be sampled the same

8i- | -) + η + 1 = 5 «+ 1 in contrast to (8n + 1) Pulses that would be required if, during the scan, the occupancy of the scanned lines no consideration would be given.

The percentage increase in connections that can be made with a given frequency band (or with the same switching speed of the components contained in the system) is therefore the same

! » + 1 Λ _ * _nn I 8 « Λ _.

- ου I ₀ .

5h

- 1 Si 100

5n

- 1

scan those lines whose signals are to be fed to the encoder, the following would Samples of a particular line are not carried out at constant time intervals. It is obvious that every time the samples of some lines between a cycle and the following would be carried out or interrupted, accidental extensions or shortenings of the Time interval would occur by the already

ίο running scans one after the other.

To avoid this, care is taken that the scans of all speech lines in all Sampling cycles and are carried out at the same time. The samples formed in this way are in special Storage capacitors stored. A subsequent scan will only give the encoder the signals of those storage capacitors which belong to the lines to be coded are supplied. The received and decoded signals are

saved. At the end of a sampling cycle, all capacitors then give their sampling values at the same time to the associated speech lines.

The invention is explained in more detail below with reference to the drawing. It shows

F i g. 1 is a circuit diagram of a terminal of a multiplex transmission system, which is designed according to the invention, and

F i g. 2 is a diagram of a transmitted pulse train used to explain the invention.

The in F i g. 1 essentially contains the following structural units:

Distribution chain

There are two distribution chains CDeI ... CDen and CDrI ... CDm , the first of which is sent to the sending side and the second to the receiving side.

As will be explained in more detail below, the invention thus solves the problem of non-

Use of the occupancy time of a certain number of remote voice connections in both directions for a similar distribution in the corresponding condensate saving bandwidth or increasing the number of possible voice connections.
without a TASI device being connected between the voice lines and the transmission channels 25
must be made by using appropriately modified and operated pulse code modulation devices.

Compared to a conventional PCM system, there is a certain increase the device costs per voice line, while on the other hand the common devices (encoders, decoders, Clock generator, line pulse repeater, etc.) through a larger number of call connections be exploited; the effort per voice line is therefore not significantly higher, so that the The use of such systems is also economical for shorter distances.

In systems in which the speaking pauses for

Establishing additional voice connections is arranged. These distribution chains are used in a similar way, it is known that the highest level of efficiency is achieved as with conventional PCM systems when echo suppressors are switched on, with the exception that between the individual stages of the prevent the received signals from being received with an electronic chain Switch CEeI ... complete alignment of the connection between the CEe η or CErI .. .CEr η , the fork circuits 45 required for each two-wire line occur again according to the switch position of the next stage on the transmission side and the channel is then bridged or not.

The mode of operation of conventional distribution chains is known, so that a brief explanation will suffice. All stages of a chain receive switching pulses at the same time, which in the present case are fed to the transmitting-side chain via a wire b and to the receiving-side chain via a wire e . However, only that stage responds to these switching impulses from a previous stage

directions prevented. As mentioned, the previous release signal was received. A start-up circuit is therefore provided for those speech lines which are provided for an AVVe or AVVr that are unoccupied by synchronous signals arriving at wires α or g for longer than a certain value for the system to be interrupted in the coding of a chain. In addition, a still-to-be-described control and the release signal for the first operating device ensure that 60 stages of the associated chain are supplied in each scanning cycle. Each speech signals of a number of speech lines, e.g. B. Head of ILN ... η LN is assigned a distribution chain level equal to or less than half the number of all. The elekan voice lines connected to the system are switched on in the chains, ironic switch CEeI. . .CEeη or Ceri ... are coded and in that in each cycle a signal CErη allow any number of coding steps performed so many new lines 65 off the chain, thereby preventing then such lines are present, the encoding is that those of the non-occupancy determined in the transmission-side memory paths were interrupted wor- capacitors MCeI ... MCe η stored Abden. If only the samples coming from the voice lines were to be used in each sampling cycle

prove this in reality free transmission direction. Of course, such an echo canceller does simultaneous transmission in both directions is impossible.

The present invention realizes a mode of operation that is functional of switching on corresponds to an echo lock and thus a simultaneous transmission in both transmission

5 6

Deactivated levels are assigned to the code on the receiving side meet the storage levels

rer are fed. MrI. . . Mrη each has a threefold task:

How the distribution on the receiving side works * - _{a) You set the electronic} switches CEl ...

chain corresponds to that of the sending-side distribution chain _{C £ n of the receiving-side} distribution chain a;

chain. On the transmission side, the distribution chain controls coding 5 _{b) they deliver to} AND circuits from the transmission side

gates PCI ... PCn, where only those gates are scanning gates PCAeI . .. PCAen a lock

are tatigt, which are switched on lines overall _{ή χ the} ⁵ _verhinder t that at the transmitting side, a managerial

hear. Analogously, controls the reception-side encryption _t is sampled, the receiving end off

division chain corresponding memory gate PMl ... is scanned

PMn which store the coded signal samples xo _{c) they control the electronic} switches CEl ...

cher capacitors MCrI. .. MCm, which correspond _{to a} preparation chain CPl. . CPn a,

are assigned to the respective voice lines, _{so that the bridging of the respective} preparatory

The electronic switch for the transmission side and control elements is caused to lead to lines

The reception-side distribution _{chain is created by correspondingly zm the reception-side spoke} .

Talking switch-on memory controlled. i ₅ mng are switched on.

Switch-on memory, preparation chain and time coincidence circuits

In a system that does not have simultaneous over- The preparation chain CPl .. .CPn is in over-

transmission of the telephone signals in both directions 20 licher way built with bistable circuits,

made possible, one would get between the electronic switch C £ l with a single switch-on . . .CEn

memory for transmission and reception, with which are switched on, an optional bridging

present embodiment of the invention are the bistable circuits allow

but separate bistable switch-on memories MrI ... Each bistable circuit in the chain controls one

Mm and MeI ... Men for the receiving side or 25 bistable memory circuits on the transmitting side MeI ...

Sending side provided. Each level of the respective menu, whereby the activation of the associated

Distribution chains is a bistable memory circuit that causes lines or not. The η levels

assigned. Since the tasks of the transmitting side of the chain are linked to form a closed ring

Memory circuit and the receiving side stores. The chain is switched on by switching off

cherschaltung differ somewhat, they are controlled in the 30 output pulses of a gate circuit B , the

the following explained separately. will be described in more detail below.

The memory circuit for the transmission side is fulfilled with each switching step of the preparation chain

with their output signals a four-fold function: a voice line switched on. As below

a) It sets the CEeI .. electronic switches. will be explained in ^more detail, the step number of the transmission side CEEN distribution chain is a; ³⁵ P ^{ro Zv} . ^{klus in the} present example is chosen so that

b) it supplies at the output a criterion which ^{that al%} ^ ^{ahl the} switched lines for indicating whether a particular line is not turned on every cycle equal to or Kiemer than half of or, ^alier to the formation of a distribution ^Araah} existing phone lines is. To control the information that is generated by a switching activation of the lines is in turn generated by the device arrangement, which is not ^{controlled here 4} ° ^{emen activation pulse} , which is shown for all, as this is common for understanding the lines, but for all those present Invention is not necessary; Lines in which a signal occurs is blocked,

c) it delivers to AND circuits from the transmitting side ^because f _u ^{exceeds a} certain threshold value, according to scanning gates PCArI . . . PCAM a barrier course be signal is not a le m a cycle that prevents a recom- ⁴⁵ switched lines to be at the transmitting end is actually occupied, the catch side scanned line is scanned blank and undesirably switched Leitun- _and however gen then in the subsequent cycle

d) it excludes electronic switches CEl ... CEn , since the above-mentioned blocking is missing in a preparation chain CPl ... CPn so that ^W1 _and ^rd ; ^Jed ^ L telephone line circuits is a Zeitkoinzidenzdaß bridging those preparations ⁵ °. Assigned to CTn. This Schaltuntungselemente is caused to the lines S ^s _{f c} ^be controlled in two ways: The include a controller which * ^lle the transmission side encoding ^{ls} fu} _o ^r circuits are common and is carried out by already switched on. ^eme threshold or trigger circuit SG, which further

This is explained in more detail below. Whenever

The individual memory circuits are two-fold controlled in a line switched on for coding, namely by a switch-on and signal is present which exceeds the threshold value activation signal. The switch-on signal is used to progress, an output pulse is generated, which all switch on a certain memory level. When time coincidence circuits are energized at the same time. That one stage has been switched on, this means that time coincidence circuits are also switched on so that the associated electronic switch is still set up a signal from an associated coding that the signal is supplied from the associated circuit gate PC 1 ... PC η, that occurs when the ruling is encoded. The activation signal causes ses gate closes. It therefore only speaks to the activation of the memory stages to which the time coincidence circuit has reached the line. The term "activation of a storage stage" from which the threshold value exceeded is understood to mean that the relevant stage originates in a signal.

If a time coincidence circuit responds, the chain stage is set to the assigned distribution corresponding speech line from the dispatcher it sends a signal at the output, which the free scanning cycle is excluded. Switching signal for the corresponding line

locks. However, if the time coincidence circuit is not energized because the line is not busy and the threshold value circuit has not responded, the output signal of the time coincidence circuit falls with a time constant that can be set between zero and any value, to a value at which an assigned activation -And gate ELl ... ELn supplies a reverse voltage. When the activation signal occurs, the relevant line is activated in the desired manner.

Activation AND gate

Each speech line is assigned a release AND gate ELl .. .ELn , which fulfills the following logical function: The release signal is allowed through or blocked, depending on whether a blocking signal from the time coincidence circuits is present or not.

the one shown in FIG. 2, the distribution information consists of η pulses, ie as many pulses as there are speech lines connected to the system. The polarity of these impulses indicates whether the corresponding speech line is to be switched on or not. The pulses are sent in such an order that the first pulse corresponds to the first voice line, the second pulse corresponds to the second voice line, and so on.

The distribution information MD is followed by normal groups Cod.l to Cod.M each of eight pulses per coded sample, of which seven are intended for coding and the eighth pulse Sei .. .Sen for signaling purposes.

It can be seen that the signaling pulses from the distribution process, i.e. H. from the coding of the Telephone signals to which they are assigned are independent.

The signaling pulses are transmitted in a fixed order for all η speech lines, regardless of whether they are included in the coding or excluded from it.

In the case of the one shown in FIG. 2 shown example in which

for the sake of simplicity η

- -γ was accepted, the signaling pulses Sei ... Sen occupy two consecutive cycles.

Also under the assumption that m = -r-

Scan gates and scan AND stages

Each speech line is a sampling gate PCAel ... PCAeη on the transmitting side and a sampling gate PCArI on the receiving side. . .PCAm assigned. the
The task of scanning gates on the transmit side is to
Time of sampling by a line filter
FLl ... FLn energy flow to the corresponding storage capacitor MCeI ... MCeη on the transmission side
allow. As mentioned, the scanning is carried out for
all speech lines at the same time. The receiving side is 30 is the number of pulse groups Cod. 1 ... gen scanning gates PCArI ... PCAm have since Cod.m equal to or less than half the number against the task, the receiving side memory all to the system connected voice lines, capacitors MCrI .. .MCm at the time of The information that the various voice reception-side scanning, which also designate for all lines whose signals in a be-voice lines occur at the same time, are actually encoded at the corresponding cycle, are the Line filters FLl ... FLn to discharge. one after the other via a wire el to the encoder

The scanning gates on the transmission side are controlled by transmits and then via the transmission path via associated scanning AND stages which carry. If in a certain cycle, for example, the signals of the lines 1, 3, 5, 6 are coded by the transmit or receive switch-on memories so that the scanning 40 is during reception, the voice lines associated with these lines are also switched on on the transmit side or in the case of codes sent in the same order. As mentioned, the switch-on memory on the transmit side uses the electronic switches to determine the lines whose samples are to be encoded in a specific cycle. In the example shown, the state of the stages of this memory as a whole corresponds to the distribution information given on the transmission path, and the formation of this information is carried out by the same transmission-side intervention. The input of the threshold value circuit is 50 switching memory controlled via the outputs ζ 1 ... in , connected to the coding input (Aderc) and assumed to be in a given cycle

the signals from ρ lines have been coded (p <to): The logic of the system is designed in such a way that a sequence of m pulses is generated for sampling the samples stored in the storage capacitors. After the ρ coding gates have been scanned, the p-th pulse is obviously supplied either directly by the -th stage of the distribution chain or by electronic switches that operate through

assumed, while the highest number of codings transmitted via the 60 associated switch-on memory into the bridging transmission path were brought into the same position. This pulse brings with _{m =} JL _se i _n S ₀ Ii its trailing edge a bistable circuit A (Fig. 1)

2 'in a position in which a gate B is opened,

After an initial sync pulse Sinl, distribution information MD is transmitted through the then the remaining (m-p) pulses. This information can pass through, so that the preparation chain can be advanced by (n - p) digits according to an arbitrary rule. After being built, which of course on the transmitting side and this forwarding, the chain remains fixed until the next receiving side and must be the same. At the cycle in the position reached and then begins

the transmission, the scanning of voice lines switched on at the receiving end are blocked.

Threshold value circuit SG

The threshold value circuit SG is designed in the usual way and switches from a zero operating state to a one operating state if the input signal overestimates a certain threshold value and the amplitude-modulated pulses coming from the coding gates are switched off. As mentioned, the output signal of the threshold value circuit controls the time coincidence circuits.

F i g. Fig. 2 shows an example of a pulse train as it is transmitted by a system according to the invention over a transmission path. The number of connected speech lines was given with η .

forwarding in the same way anew. The leading edge of the pulse mentioned, on the other hand, supplies the activation pulse which, as mentioned, causes the activation of those lines for which the time coincidence circuit is de-energized; this takes place before the continuation of the preparation chain. The bistable circuit Λ is returned to the idle state by synchronizing pulses. As mentioned, all those stages are switched off from the preparation chain which are switched on on the transmitting side and / or on the receiving side; this is done by the electronic switches that are provided between the chain stages. The m - ρ impulses thus cause a corresponding number of lines to be switched on at the transmitting end, which are definitely not switched on in either of the two directions at this moment. It is clear from the above explanations that the total number of lines switched on in the individual cycles can never be greater than m . Some or all of the m - ρ ao switched on lines may not be occupied at the transmitting end, but in this case the associated time coincidence circuit will not be excited by the threshold value circuit, and the activation pulse of the next cycle as will cause these lines to be activated.

It has already been mentioned that, at the same time as the sync pulse, all lines that are not switched on at the receiving end are scanned at the same time on the transmission side. The samples obtained in this way are stored in the corresponding storage capacitors, and then some of them are passed on for coding. On the receiving side, the switch-on memory assumes the status in each cycle which corresponds to the distribution information coming from the corresponding terminal. The device for receiving and forwarding the criteria contained in the distribution information is shown in FIG. 1 is not shown as it is not essential to an understanding of the present invention; this device is connected to the levels of the receiving-side electronic switch memory via wires hl ... hn.

The electronic switches are prepared so that each one through the storage gate the decoder charges the corresponding storage capacitor via a wire / incoming signal. At the same time as the sync pulse, all stored sample values are simultaneously transmitted by the receiving-side Sampling gates given to the associated line platters; it is in this context mentions that in the respective cycles the gates of those lines are not actuated which are switched on on the transmission side.

With the present arrangement, only a single line filter is required for transmission and reception: The send-side and receive-side AND circuits that are created by the receive or transmit memory are controlled, ensure that a filter can only be switched on in the transmission circuit can if it is not switched into the receiving circuit, and vice versa. The blocking on the transmission side the activation of channels activated on the receiving side and the function of the transmitting side and sampling gates at the receiving end make it impossible for a received signal to be re-transmitted will. This eliminates the need to use an echo canceller and hybrid circuit.

Claims (4)

Patent claims: 1. Time-division multiplex transmission system for telephone signals that are transmitted on η voice lines, each of which can be occupied or unoccupied, with a multiplex transmission device which comprises a number m, which is less than η , of transmission channels to which samples are assigned in a sampling cycle are, in which each transmission channel also corresponds to a certain period of time for the transmission of a speech signal, and with a coding device for the samples, characterized in that a group of gate circuits (PCAeI ... PCAen), which are controlled by low-pass filters (FLl ... FLn ) are connected to the speech lines (ILiV ... nLN) , at the transmitter side, the simultaneous scanning of the speech signals of all occupied and unoccupied lines that are not scanned in the same scanning cycle on the receiving side is carried out, with such double scanning being responsive to a scanning synchronous pulse and the receiving-side speech line status AND spouse r is prevented; that the sampled values of the voice line signals are stored in memories (MCEl .. .MCEn) until gate circuits (PCI .. .PCn) are activated in sequence which connect the memories to the line (el) transmitting the sampled values of the encoder and which in turn can be controlled by a distribution chain consisting of trigger circuits (CDeI ... CD en) , which are controlled simultaneously with periodic pulses and successively emit actuation pulses for the gate circuits, and which are also assigned memory circuits (MEl ... Men) that enable the actuation of the cause the occupied voice lines corresponding trigger circuits and thus gate circuits, the seizure state is determined by a threshold value circuit (SG) , which responds to the sampled values and delivers a corresponding signal to the memory circuit, which excludes those trigger circuits from the distribution chain that the previously occupied, releasedc speech lines held and in this state for a time which is shorter than the time set by time coincidence circuits (CTl ... CTn) correspond to speech lines remaining, so that exclusion of the occupied speech lines during the pauses between word syllables is prevented; that the memory circuits (MeI ... Men) send a distribution message to the remote station via separate outputs (/ 1 ... in) , which consists of a sequence of pulses which correspond to the voice lines with their temporal position and indicate whether the respective Line is to be regarded as occupied or unoccupied; that on the receiving side a line (/) for transmitting the samples coming from the decoder from the remote station through a group of gate circuits (PMl ... PMn) is successively connected to capacitor stores (MCrI ... MCm) , which in turn are connected to the corresponding Speech lines connected gate circuits (PCArI. .. PCAm) are connected, of which at the same time at constant 809 574/13 * Clock only those are operated that connect the capacitor store with the speech lines (ILiV ... itLN) via the filter (FLl ... FLn) and that are not operated in the same sampling cycle on the transmit side, the operation of the other circuits by AND gates which respond to the activation pulse of the gates and the state of the transmission-side lines, and that a series of memory circuits (MrI ... Mrn) receives via separate inputs (M ... hn) one of the sent distribution information, whereby the mentioned Group of gate circuits (PMl ... PMn) is actuated via a receiving-side, consisting of trigger circuits (CDrI ... CDm) distribution chain. 2. System according to claim 1, characterized in that the transmission-side, from trigger circuits (CDeI ... CDen) existing distribution chain has a number of electronic switches (CEeI ... CEeη) , which switched between the trigger circuits and through the transmit memory circuits (MeI .. .Men) are controlled and which exclude the trigger circuits assigned to the unoccupied telephone lines from the distribution chain, and that the distribution chain on the receiving side, which also consists of trigger circuits (CDrI ... CDm), has a number of electronic switches (CErI ... CEm ) , which are connected between the trigger circuits and controlled by receiving memory circuits (MrI ... Mrn). 3. System according to claim 1 or 2, characterized in that one of trigger circuits (CPl ... CPn), between which there are electronic switches (CEl ... CEn) , checks the existing ring preparation chain on the unoccupied voice lines and the corresponding Gates (PCI .. .PCn) for letting through the samples of the line signals for coding and transmission when the samples arrive, prepared, with those trigger circuits being switched off by the switches from the preparation chain, which the memory circuits (Mel ... Men) on the transmission side as occupied voice lines correspond, and that to check for the unoccupied voice lines in each scan cycle, the preparation chain is advanced by as many positions as the difference between the number of available channels and the number of channels actually occupied during transmission. 4. System according to one of claims 1 to 3, characterized in that the scanning of the occupancy state of the voice lines, whose signal samples are output for transmission, is carried out by a single threshold circuit (SG) whose input is connected to the transmission line (c) and the output of which leads to the inputs of time coincidence circuits (CTl ... CTn) , at the other inputs of which the signals from the trigger circuits (CDeI ... CD en) of the transmission-side distribution chain arrive and their outputs to the inputs of coincidence circuits (ELl ... ELn lead) receiving the from the last trigger circuit (CType) of the distribution chain next to the further inputs signals and) delete the transmission side memory circuits (MeI ... Men, if the threshold circuit (5G) on the transmission line samples for a time which is longer than the time determined by the time coincidence circuits (ZTl ... ZTn) is smaller than the threshold value stay. Considered publications:
German Patent No. 604 025;
German interpretative document No. 1072 656. 1 sheet of drawings 809 574/134 4.68 © Bundesdruckerei Berlin