DE1145237B - Multiplex transmission method and circuit for carrying out the method - Google Patents

Description

GERMAN

PATENT OFFICE

S 64364 IXd / 21a ⁴

REGISTRATION DATE: AUGUST 10, 1959

NOTICE THE REGISTRATION ANDOUTPUTE EDITORIAL: MARCH 14, 1963

The invention relates to a multiplex transmission method for a transmission system, consisting of Transmitters and receivers, signal storage devices, devices on the transmitter for recording Character signals of a number of channels in the memory devices to form a rectangular matrix and means at the receiver for splitting the signals to the channels, as well as one Circuit for carrying out the procedure.

The invention finds important application in, inter alia, multiplex telephone systems for the transmission of speech signals, but can also be applied to systems that provide other information transmitted as telephone signals, namely video signals and data signals. You can on transmission over lines are used that have concentric lines and waveguides, and also to the transmission over radio lines.

With the multiplex systems used up to now, it was common practice to sort the signals according to frequencies divided, to be transmitted simultaneously, with a separate carrier wave with a separate frequency for the Transmission of every signal was provided. Such a system requires a large number of carrier frequency generators and a corresponding number of tuned receivers.

There is also a method in use of time division for simultaneous transmission is used in which the transmission path with each signal source by connecting in faster periodic order is coupled. With these arrangements, however, the number of channels is limited, because the signals transmitted in fragments have a sufficiently long time interval need to avoid crosstalk.

The main purpose of the invention is to provide an improved time division multiplex transmission method at which is more for a given bandwidth compared to known systems of this type Channels can be transmitted.

The multiplex transmission method according to the invention is characterized in that on the On the transmitter side, the signals to be transmitted from the individual channels in periodically recurring sequences are recorded in the storage devices on as many columns (or rows) as there are channels are, whereby the signals of the same channel are stored in each column (or row) and that the storage devices are scanned in a direction perpendicular to the storage direction are, whereby, in each case the signals of the multiplex transmission method and circuit for implementation

of the procedure

Applicant:

Associated Electrical Industries (Woolwich) Limited, London

Representative: Dipl.-Ing. E. Schubert, patent attorney, Siegen, Oranienstr. 14th

Claimed priority: Great Britain 11 August 1958 (No. 25 744)

George Helier Foot, Esher, Surrey,

and John Edward Flood, London (Great Britain),

have been named as inventors

same channel can be transmitted as a signal group to the receiver of the transmission system.

By recording in columns and reading in rows (or vice versa), instead of one transmit a short sequence of signal pulses one after the other and save time achieved, since in order to avoid crosstalk between the channels, only the time interval between successive signal trains must be present and no time interval between each single pulse of a signal piece, as in the usual arrangements, is required.

To carry out the method according to the invention, there are two storage devices on the transmitter and two more provided on the receiver as well as a switching device, whereby if a tube one each pair reads, the other records and then the activities or processes are switched.

A development of the invention is that a device is provided through which the Sampling jumps to the next channel if there are no signals for a specific channel. In addition, a device can be provided to connect the circuit on the receiver with the transmitter circuit to synchronize, which can be done by transmitting suitable synchronization pulses. Such Synchronization pulses can be generated after each signal

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group (for example after, twelve signal pieces) interspersed pulses of large amplitude or opposite Be polarity. These pulses can be screened out at the receiving station and used for propulsion of a distributor. After each complete cycle, for example over the entire Memory matrix, a longer pulse or a coded group of pulses can be sent out. The storage of each signal is continued indefinitely, but limited in practice by that the delay caused thereby does not cause any hindrance to the person who receives the signals. For example, in the case of a telephone conversation between two people the delay last a few milliseconds. When using this procedure, the individual Carrier frequencies and frequency filters, which are required in frequency multiplex systems, are superfluous. At the same time, the required frequency bandwidth is less than in the case of a conventional time division multiplex system.

The invention will now be described in more detail with reference to FIGS. 1 to 12, namely shows

Fig. 1 is a schematic view of the memory matrix at the transmitter,

2 shows a schematic view of the memory matrix at the receiver,

3 shows the mode of operation of the arrangement according to FIG. 1,

4 is a block diagram of the memory circuit of the transmitter,

5 is a block diagram of the memory circuit of the receiver,

6 shows a block diagram of the circuit for the sampling generators of a memory;

7 shows the course of the switching and scanning voltages,

8 shows a circuit of the staircase voltage sampling generator;

9 shows the form of the transmission signals with synchronization pulses,

10 shows the form of the synchronization pulses and the course of the scanning voltage at the receiver,

Fig. 11 shows a sync separation circuit for the receiver and

Figure 12 shows a circuit for the time allocation speech intermediate circuit.

In the description it is assumed for the sake of simplicity that the recording at the transmitter in Columns and reading in lines, while the receiver records in lines and the Reading is done in columns. However, arrangements that operate in reverse can of course just as well be used.

In the memory matrix (grid) on the transmitter according to FIG. 1, the recording is carried out in vertical scanning each column is carried out one after the other from top to bottom and from left to right. During the When recording, signal pieces from each source are recorded in sequence in memory, with the Recording is done downwards and the distance between the records is the same, so that in In each row of the grid, all signals are or will be connected to the same channel.

The recording occupies an entire scanning field, and a recording scanning field is followed by a reading scanning field, in which the storage tube is scanned horizontally, as shown in FIG. As each If a row contains signals from the same channel, the end result is a short signal group for each one Transfer channels in sequence. When reading at high speed, the time can be shortened of the signals can be achieved, so that in this way it is possible to record a large number of Channels at the same time. The recording is carried out accordingly at the recipient of the ίο received signal trains at high speed horizontally, corresponding to that shown in FIG Grid, while the reading is then carried out vertically and the signals on the assigned Receivers are distributed in the form of periodic pulses.

Figure 3 illustrates the time reduction result achieved by the invention. The upper part of the figure shows the effect of transmitting signals from six channels in the form of periodic pulses. In the figure three consecutive pulses of each channel are shown. In the upper part of the figure, the groups are denoted by the reference symbols I, II and III. Since each signal piece lies next to a signal piece of another channel, a suitable interval must be provided between successive pulses in order to avoid crosstalk. If, however, the character pulses are arranged in successive signal trains, as shown in the lower part of the figure, only one interval needs to be provided between successive signal groups, so that a considerable time saving can be achieved, since the signal trains can be shortened in time, provided that they are sufficiently separated from neighboring signal trains or other channels. Fig. 4 shows in block form the memory circuit of the transmitter. A number of input channels 1 to η are fed through assigned transmission gates shown on the left in the figure, the transmission gates being actuated one after the other, so that each channel is connected to memory and B in turn. The memories A and B alternately record time segments and are controlled by gates Gl, Gl, G3 and G4. Control signals α and b are alternately supplied to the gates, so that the opening of gates Gl and G 4 alternates with those of gates G 2 and G 3. If Gl and G4 are open for a period of time, the incoming signals are fed through gate Gl and recorded in memory A. At the same time, the signals in memory B are read and passed through gate G 4 to the transmission channel. After the scanning of a matrix has ended, the signal α ends and the signal b comes. Now gates G 3 and G 2 are open and gates Gl and G4 are blocked. Therefore, the information that was previously recorded in memory B is now read and transmitted while the next period of information is recorded in memory B at the same time.

Fig. 5 shows the corresponding circuit on the receiver, which works in the same way. The incoming signals are fed alternately to a memory C and a memory D , while the information is recorded in the memory C and information in the memory D is read and passed through the appropriate receivers connected to the corresponding channels 1 to η . It is controlled by signals α 'and b',

5 6

control gates G5, G 6, Gl and G8. The rises to earth potential, so that one at the collector

Signals d and V are, for example, diode D 2 connected to signals α and b of transistor VT 2

of the transmitter synchronized, and it follows that with conducts, whereby the capacitor C 2 discharged and the

the arrangement shown, each transmitter memory output voltage increased to the ground potential

always signals to the same receiver memory 5. The cycle is then repeated continuously,

transmits. The cathode ray tube storage is required

If the grid is not square, a penumbra pattern is of course to be saved and it with

borrowed different line and column scanning speeds to reproduce the degree of linearity that is used for speech

necessary during reading in relation to the or other applied transmissions

The speeds required when recording. A well-known tube that meets these requirements

can be used. is called Radechon.

In Fig. 6, which illustrates in block form how the Radechon tube is an electron beam this can be done, separate line generators are storage tubes. The target consists of one for reading and recording and similar separate thin plate made of electrical insulating material. the Column generators for reading and recording 15 one side of the isolation plate is represented by a metal. During the recording, the plate is covered and a fine sieve stands with the Signal α gates G 9 and GIl supplied so that the other side is in contact.

Row and column recording generators with the The surface of the insulation forms one egg

Memory / 4, which is shown in Fig. 4, connected to a capacitor, while plate and sieve

are and also during reading the reading 20 form the other element.

line and column generators with the deflection anodes The signals are in the form of electrostatic

of the store A via gates GlO and G12, which are stored by energy, either by

the signal will be opened. placement of electrodes on the sieve or by removing

The synchronization is carried out by line syncronization of electrodes from this,

nisierimpulse PA preserved, the line generators 25 During writing, signals after the

and transmitted through the column synchronizing beam generation system during the

impulse PB, the beam fed to the column generators, scans the target. During the departure

will. reading the target is scanned again where ^

Fig. 7 shows the shape of the control signals α and b, in the sieve, which at a high impedance

which is rectangular and of duration T which is kept equal to 30 to earth, to a preamplifier

is the duration of a matrix scan. The line is connected, which amplifies the output signals,

The scanning generator produces a normal sawtooth chip This tube has a barrier grid immediately in front of it

tion, for which every known generator is used, the anticathode, which is a redistribution of the

can. The column scan generator prevents pre-charges from being generated across the anticathode as they occur at

preferably a staircase voltage, as occurs through the many other storage tubes. Signals can

Form C is shown in Fig. 7, the length m of the tube being recorded, namely

of each step is so large that a line scan is neither by

can be carried out. a) these to the electron tube or generation

Fig. 8 shows a suitable transistor circuit for system control grids to be fed while

Generation of a voltage, the course of which is C, in FIG. 7 4 °, the anode is kept at a constant voltage

is shown. will, or

This circuit has the following mode of operation: b) They are fed to the anode while the A rising pulse / charges the capacitor C1 control grid potential is kept constant, through the transistor VTl, whose emitter-base The last method has the great advantage that distance is biased by the pulse. The 45 automatic erasure of old information by diode Dl is reverse biased and non-conductive. new information is recorded. At the end of the pulse, the voltage at am is therefore preferred for use in the time-shortening emitter of the transistor VT1 and the cathode of the multiplex memories. Diode Dl accordingly. The diode Dl conducts, and the signal can from the tube with HiKe one of the transistor VTl is blocked. 50 load resistance can be read, the ent- The capacitor Cl, which was previously charged via the tran- neither to the shield or the anode circuit ansistor VTl , is then discharged via closed. It is important that the required diode D1 and capacitor C 2 be connected to ground. The output signals from the input signals as well as from the charge of the capacitor C1 is transferred to the volatile pulses that are transmitted by switching the capacitor C2. When the condenser Cl is discharged, the diode Dl stops conducting. to be separated. This can be done, however, the transistor VTl remains blocked, so that recorded with direct current pulses and with the capacitor C 2 read the accumulated charge of alternating current signals, which stores. When another / -pulse arrives, the beam has a superimposed high-frequency modulation. the process is repeated, the capacitor Cl 60.To ensure that the system works correctly and then transfers its charge to, the generator of the receiving station must have the capacitor C2. This can be done by row and column synchronizing charge and the output voltage on it, step pulses that are contained in the signal, wisely increased, in almost the same steps. 65 which is sent over the common transmission channel after a certain number of / -impulses, as is done with television. A signal composed in this way, a negative pulse K switches a transistor VT 2 is shown in FIG. 9 therein. The collector voltage of the transistor VT 2 is set. The line synchronization pulses can be pulses

7 8

greater amplitude or opposite polarity would have to exceed the weakest speech signals that are transmitted to the input channels after each group of signal characters and noise voltages. rarely exceed it. Since the voice signals Fig. 10 shows the synchronizing pulses of the receiving AC signals, transmission channel gates are used and Fig. 11 shows a suitable synchronizing circuit which has both positive and negative pulse separating circuitry. At the receiver, the pulses are sent, depending on the polarity of the input line synchronization pulses, which are generated by a line signal (symmetrical transistor gates are allowed through for this LSS synchronized separator, suitable for this purpose). Two discriminators are used, a line scan generator LSG and circuitry. A discriminator enters a distributor (not shown) to trigger channel io activity when a character amplitude generates a given pulse group. One long pulse can then exceed positive voltage, and the other is sent after each complete column in order to initiate scanning if the amplitude of a negative span exceeds a column scan generator FSG for the next scan of the same size. The column synchronization pulse The one shown in the dashed square can of the line synchronization pulses with the aid of 15 device belongs only to the channel M. It is the same as an integrating or differentiating circuit FSS for each channel. The rest of the device is used to all be separated. Channels together.

The number of speech channels that have a single trip circuit Tm connected to each channel

The transmission path of the given bandwidth is sent to the outputs of the two discriminators, can be connected through the behavior of the intermediate 20 via a gate GIm, which

circuit opened by time allocation voice interim through the corresponding channel pulse PM

switching or temporal voiceband allocation is made when an impulse passes through a channel transmitter

heights. In the method, the circumstance is made up during the recording scan of the memory

used that each channel is generated in a multiplex remote, the threshold value of a discriminator Speech system on average exceeds language in less than 25.

half the time. Characterized in that an excess After completion of the recording scan betragungskanal a speech input channel, only supply of the memory A starts its Ableseabtastung that is rejected if in the latter a signal through the in Fig. Synchronisierbefindet 10 shown, it is possible to almost 2 η independent sound impulses is controlled. The synchronization pulses channels via a channel multiplex transmission system 30 are also transmitted to the common transmission. routed away via a gate G13. At the end of each line, the signal pieces are monitored during the synchronization pulse PA , a counter CR monitors a point in the recording process in order to determine whether signals are present and to determine whether signals are present. When all of one generate the output line. Each level of this channel received character has the amplitude zero 35 counter corresponds to a channel in dtem, so the horizontal line on which this system, whose output line is stored with a corresponding character, is connected during the reading-speaking TorG2m. In Fig. 12, scanning is omitted. As a result, the time that stage m is connected to TorG2m. If the transmission of the signals takes up, the short time the trip circuit Tm is not actuated (because none as it would be if all lines were scanned. The number of channels whose signals are present in each), so the gate G 2 m cannot be sent in column, can therefore almost be carried out, and the line scan generator will not be duplicated. The must be released at the recipient end. However, the pulse PA goes to the common line in the memory also during the transmission path via a gate G13 and the recording column will be omitted. Also transmitted to the column scan generator at 45. Reading column or scanning are all lines in The latter changes its output voltage by normal way of scanned and the exact output- a step that causes it to form the beam to signal for each channel. to divert the next line without scanning a line. Subsequent PA pulses switch the information for each channel to be stored, 50 counter by one position, until the counter reaches a position that is zero or whether at least one non-zero character corresponds to the channel Characters during the Aufist. Diesel information determines whether the corresponding drawing scan has formed. Line in memory is scanned when reading. B. the channel m characters during the opening or not. The same information must also have been formed by the 55 drawing scan, so the trigger-receiver end is transmitted where it determines circle Tm in the operating state. Then pulse PA goes whether or not the corresponding line in the memory is scanned by the gate G2m, triggers the line scan generator recording. An off and thereby causes the memory to read its appropriate circuit in order to do this in stored signals for this channel. Wäh-Fig. 12 shown. When the line scan generator is in operation, it prevents further PA pulses from being sent to a gate G14. Memories are (+) and (-) discriminator circuits connected at the end of the line scan, gate G14 weighs open. A discriminator consists of the, and the next Py4 pulse brings the Schmitt tripping circuit, which is known to the counting device, and can be set so that it switches to the next position so that it only delivers an output. This process is repeated until the end of the when its inputs have a certain column sampling period. The column sync pulse exceeded threshold. This threshold value PB then resets the column scan generator should be set so that it all, with off as well as the counter CR and the trip circuits

TM. The PS pulse is also transmitted to the common transmission path via G 13. During the column synchronization pulse, the line synchronization pulses are again suppressed at gate G 14.

The signal sent over the common transmission line consists of PS pulses, PA pulses and the signals that have been read from the memory. During the sections of the scan in which there are no signals in the memory, the PA pulses follow one another in close succession. When a stored signal is encountered, an interval equal to the line scan period occurs between two PA pulses, and the signal stored on a line of memory is transmitted during this interval. In this way, the duration of each field scan can be less than η times the line scan period, thereby making it possible to increase the number of channels for a given bandwidth of the common transmission path.

This arrangement saves time, but requires the same memory area. However, since the The duration of the sampling time segments must be the same, more signals can be transmitted during a sampling period will.

The gates used can be conventional diode circuits and the counter CR can be a conventional chain circuit using tubes or transistors. The trigger circuits TM can be conventional Eccles-Jordan trigger circuits, also using tubes or transistors. If the number of channels in the system is small (e.g. twelve) and the pulse periods used are quite long, ferrite core memories can be used. Each ferrite core can combine the functions of the trip circuit TM and the gate GIm and G2m. If the number of channels in the system is large (e.g. 600) and the pulse periods are very short, a common delay line or cathode ray tube memory can be used to replace the individual trigger circuits Tm . If a cathode ray tube memory is used, the tube which also stores the speech characters for this purpose can be used. When TASI (Time Assignment Speech Interpolation) is used, the TASI information signal is recorded at the end of the line containing the speech characters. The reading process can then be carried out in the opposite direction to that previously considered. The TASI signal is read from the memory in front of the speech characters and can be used to control the line scan generator.

At the receiver end, the column synchronization pulses PS and the line synchronization pulses PA are received from the common transmission line and separated in the usual manner. These pulses are then used to operate the column and line scan generators. The line scan generator is a circuit that is reset by receiving a PA pulse. If no signal characters are transmitted, PA pulses are received in quick succession. Therefore, the line scan generator is quickly reset each time it begins to operate to generate a scan. Each PA pulse also switches the column scan generator and causes it to deflect the beam to the next line. When signal characters are sent, the interval between PA pulses is the full line scan period and the line scan generator can complete its scan. During this scanning, the transmitted speech characters are stored in the transmitter. At the end of the scan or the column, the column scan generator is reset by the PB-PuIs. During the subsequent reading scan, the speech characters are read from the memory and distributed to the channel receiver ports. Although the description describes the use of two storage tubes as transmitter and receiver, a single tube with two beams can also be used.

Claims (8)

PATENT CLAIMS: 1. Multiplex transmission method for a transmission system, consisting of transmitter and receiver, signal storage devices, devices on the transmitter for recording character signals of a number of channels in the memory devices with the formation of a rectangular matrix and devices on the receiver for dividing the signals to the channels, characterized in that, that on the transmitter side the signals to be transmitted of the individual channels are recorded in periodically recurring sequences in the memory devices on as many columns (or rows) as there are channels, whereby the signals of the same channel are stored in each column (or row) are, and that the storage devices are scanned in a direction perpendicular to the storage direction, whereby the signals of the same channel can be transmitted as a signal group to the receiver of the transmission system. 2. A circuit for performing the method according to claim 1, characterized in that the signal storage devices each consist of a cathode ray storage device. 3. A circuit according to claim 2, characterized in that two signal storage devices are available on the transmitter and switching devices through the signals alternately in the recorded in both memories, so that one memory records while the other is read. 4. A circuit according to claim 2 or 3, characterized in that row and column scanning devices for recording and row and column scanners for reading and switching means are provided around the record scanners and alternately supplying the reading scanners to the deflection control of the storage device switch. 5. Circuit according to one of claims 2 to 4, characterized in that in the memory devices on the receiver side the received signals in periodic scanning parallel to the formation of a rectangular matrix recordable in such a way that each sample corresponds to a signal group of the same channel, while to read the matrix this in a 309 539/300 can be scanned in the direction perpendicular to the storage direction. 6. A circuit according to claim 5, characterized in that the storage devices on the receiver side have row and column synchronization devices to which synchronization signals from the transmitter to trigger these scanners. 7. Circuit according to one of claims 2 to 6, characterized in that each memory device Row and column scanners for both recording and Having reading and a device is provided with which the scanning devices for the read lines to be read are only triggered if signals from the channel during recording that corresponds to this line. 8. Circuit according to claim 7, characterized in that that incoming signals via a threshold value discriminator and a control device are fed to a gate which is open when the signals from the control device and received by the discriminator to send trigger signals to the scanning geae? rator for the lines to be read. Considered publications:
Austrian patent specification No. 175 608. For this purpose 2 sheets of drawings