DE2758109A1 - SYSTEM FOR MULTIPLE USE OF A TWO-WIRE SUBSCRIBER CONNECTION CABLE IN THE TELEPHONE SWITCHING NETWORK - Google Patents

Description

27b81Q9

W. Kaiser 14-1

System for multiple use of a two-wire subscriber line in the telephone switching network

State of the art

The invention relates to a system for multiple use of a two-wire subscriber line in the telephone switching network with an exchange device and one via this remote-fed subscriber device.

One such system is the subscriber carrier frequency system Z1T, which is, for example, from "Siemens-Zeitschrift (1971), Issue 7, pp.455 to 459 "is known. It allows double use of a two-wire subscriber line connected to the telephone exchange through two telephones that can be operated completely independently of one another.

task

It is the object of the invention to provide another system for

To indicate multiple use of a two-wire subscriber line, the digital transmission of speech and / or data between several terminals located at the subscriber, which can be operated independently of one another and switching over a single two-wire line in allowed in both directions of transmission.

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solution

The object is achieved with the means specified in claim 1. Further developments are the subclaims removable.

description

The invention will now be explained in more detail with reference to the drawings, for example.
Show it:

1 shows an overview of the system according to the invention, consisting of subscriber device, two-wire subscriber line and trunk device, and the channels connected to it;

2 shows the structure of the time division multiplex frame used;

Fig. 3 diagrams to explain the directional separation
on the two-wire subscriber line;

FIG. 4 shows a block diagram of the exchange device AG from FIG. 1;

5 shows a block diagram of the signal converter SWA of the
Official device according to Figure 4;

6 shows a block diagram of the subscriber unit TG
from Figure 1;

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FIG. 7 shows a block diagram of the signal converter SWT of the subscriber device according to FIG. 6;

Fig. 8 the switch-on loop of the power supply of the exchange device and the subscriber device.

The system according to the invention for multiple use of the two-wire line between a subscriber and the latter assigned telephone exchange, i.e. the local exchange, consists of the subscriber device TG located at the subscriber and the one at the telephone exchange, also called office, located Amtsgerät AG. Both devices are connected to one another via the subscriber line that can be used multiple times. Are to the subscriber device In the present exemplary embodiment, two data terminal devices DEE (e.g. fax machines) with an over- connection speed of 48 kbit / s, furthermore a conventional telephone set and finally a BFS office typewriter with a transmission speed of 300 bit / s. In a corresponding manner, the office device AG is both with the data exchange DV and with connected to the telephone exchange FV, the channel assignment being fixed and that on the subscriber side corresponds exactly. As in the case of the known subscriber TF system Z1T mentioned at the beginning, the exchange device AG is connected to the exchange battery, whereas the subscriber device TG is connected to the exchange battery is powered remotely via the exchange device and the subscriber line.

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The information transmission for the various voice and data channels is carried out in time division multiplex. The information from the various channels is combined to form a time-division multiplex frame, the division of which is shown in FIG. If a transmission speed of 192 kbit / s is made available for all channels to be transmitted, a frame length of 24 bits _{results with a frame repetition frequency of 8 kHz, ie with a frame duration of T R = * 125 ns.} Should

di _e voice signals as well as the data signals of the two data terminal devices DEE provided channels with a transmission speed of 48 kbit / s per channel 6 bits per frame are used for the transmission of further Signals free. One of these 6 bits is used as a frame syn chronisationsbit, one for the transmission of signals of the asynchronous data channel provided for the BFS office teleprinter with a transmission speed of 3OO bit / s, one for the transmission of dialing pulses from Subscriber to the office, or of charge impulses from the office to the

Participant, one as a status bit for data channel 1

48 kbit / s, one as a transmission control bit (e.g. for parity monitoring) and one is used as a status bit for data channel 2 with 48 kbit / s. These are one after the other the first, the second, the 9th, the 10th, the 17th and the 18th bit of the frame containing 24 bits. Bits 3 to 8 are used to transmit 6 bits from the 48 kbit / s voice channel, bits 11 to 16 to transmit 6 bits from the 48 kbit / s data channel 1 and bits 19 to 24 for transmission of 6 bits from the 48 kbit / s data channel 2 are used.

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In this way, a time division multiplex frame is formed both in the subscriber unit and in the exchange unit. Around To transmit multiplex signals on the two-wire line in both directions are devices for directional separation necessary. This directional separation takes place through time separation, as will now be explained with reference to FIG will.

On both sides of the two-wire line, the transmitter and the receiver are directly interconnected in the operating state. The directional separation takes place in that neither side A, the switching side, nor side B, the subscriber side, is transmitting and receiving at the same time. For this purpose, the data signals to be sent, which the multiplexer provides at a speed of 192 kbit / s, are combined into blocks on each side, the content of which is expediently the same as that of the multiplex frame or a multiple thereof. In the simplest case, a block contains exactly one multiplex frame, i.e. 24 bits. The sender of point A, which corresponds to the exchange device AG, first sends a block with 24 bits. After a running time T _T, this block arrives at point B, which corresponds to the subscriber device TG. After receiving the last bit, the sender at B begins to send a block, usually of the same length, which is then received at A after a transit time T. After a certain pause, the sender starts at A with the sending of the next block, and the alternating sending and receiving is repeated. The cycle time T ₂ between two successive blocks transmitted in one direction is - if the block content and frame content (24 bits) are the same -

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determined by the frame duration T_. So it is T _Z = T _R = 125 \ is. Since a block is also sent in the opposite direction within the cycle duration / this means that the sender must send the digital signals supplied by the multiplexer to each point at at least twice the speed of the speed (192 kbit / s) at which the multiplexer provides them . In other words: the block duration T_ may be at most half as long as the frame duration T_, which is equal to the cycle duration T _z . The transmission speed on the two-wire line is therefore effectively around 400-600 kbit / s.

If between the subscriber device and the exchange device regenerators are required, the directional separation must take place in sections in the manner described.

FIG. 4 shows a block diagram of the central office device AG from FIG. In the operating state, the two-wire line is connected directly to the digital transmitter and receiver via a relay contact t2, the control of which is explained with reference to FIG. The transmitter receives the _2U transmitting data signals from the multiplexer. This receives from the data exchange DV asynchronous data signals with a speed of 300 bit / s and twice synchronous data signals with 48 kbit / s each. The multiplexer receives voice signals and signaling characters from the telephone exchange FV via a signal converter SWA, which converts them into digital signals at a rate of 48 kbit / s. All input signals are combined by the multiplexer to form time-division multiplex frames according to FIG. The ones received by the remote station

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The demultiplexer breaks down time division multiplex frames into individual data streams, of which the signals of the data channels direct the data exchange DV and the signals of the voice channel is only supplied to the telephone exchange after conversion into analog signals in the signal converter SWA will. If digital switching of the voice channel is possible in the telephone exchange, the Signal converter SWA either bridged or omitted. The signals RI, RE, GI and SI that the signal converter SWA emits and receives, respectively, will be explained later.

A control unit marked as "multiplex and direction control" ensures the correct formation and splitting the multiplex frame and for the directional separation on the two-wire line. It is therefore on the output side connected to the transmitter, to the multiplexer, to the receiver and to the demultiplexer. At their entrance Just like the SWA signal converter, it receives clock signals with a frequency of 48 kHz via a clock generator, which is controlled by the clock of the data exchange DV, if a synchronous data transmission via the telex and Data network is to take place. Otherwise the clock generator runs freely and supplies its own independent Tact. A device marked as "power supply", which is explained in more detail with reference to FIG. supplies the remote feed current for the subscriber device as well as the supply voltage for the exchange device from the exchange battery. It also switches with its relay contact t ~ »whose function will be explained in more detail, the two-wire subscriber line between the common connection K of transmitter and receiver and the switch-on line. The switch-on line serves to switch on the power supply.

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The subscriber device, the block diagram of which is shown in FIG shows, is in principle exactly the same as the exchange device (Fig.4), so that the corresponding devices do not need to be explained separately. Instead of the clock generator, there is a clock recovery circuit, e.g. in the form of a phase-locked loop, which derives the clock from the message blocks received in the receiver. The provision of the supply voltage is provided by a facility and its functions are marked with "switch-on loop, voltage transmitter and loop closure detection". This facility will explained in more detail with reference to FIGS.

The signal converters SWA provided for each voice channel represent an essential part of the two devices AG and TG (in the central office device AG) and SWT (in the subscriber device TG).

5 shows the signal converter SWA of the exchange device. The signal converter is connected with the terminals a and b to the telephone exchange FV shown in FIG. Further The input signals are the received digital voice signals with 48 kbit / s from the demultiplexer, which is yet to be explained binary signal SI also from the demultiplexer, as well as the 48 kHz clock signals from the clock generator.

The two-wire line connected to the telephone exchange is connected to effäsmuittaiFS & iaxeier via a fork-type transformer to transition to a four-wire line, but is galvanically separated from them. From the telephone

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analog voice signals originating from the intermediary reach the input of the delta encoder via the fork transmitter, which converts them into digital signals with a bit rate of 4 8 kbit / s. In the opposite direction the received digital voice signals are converted into analog voice signals by the delta encoder at 48 kbit / s, the current on the one leading to the telephone exchange Two-wire line can be superimposed over the fork transmitter. Instead of the delta modulation, another digital transmission method, such as PCM or DPCM be used.

In addition to the voice signals, audible tones (ringing tone, dialing tone, etc.) are also sent from the operator to the voice subscriber. to transmit the 25 Hz call and the 16 kHz charge pulses.

In contrast to the audible tones, the 25 Hz call and the 16 kHz charge pulses cannot be used with the for the Voice transmission used digital transmission method (delta modulation) are transmitted. You need to in the office-side signal converter SWA into digital signals uroge forms to be transmitted within the time-division multiplexed frame to be able to. In the subscriber device, these digital signals must be converted back into an acoustic signal or into 16 kHz pulses.

So is of the incoming from the telephone exchange to the terminals a and b of the exchange, for the connected voice subscribers determined 25 Hz ring signals in a facility called "Caller ID" logical signal RI derived, namely, let RI = L at Reception of a 25 Hz ringing signal and RI = O during the pauses in the call.

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The call recognition circuit also provides the 25 Hz call pulses at output terminals RE, which it uses a transformer from the signals arriving at the terminals a, b from the telephone exchange FV. These 25 Hz ringing pulses are used to switch on the power supply in the event of an incoming call, as shown in FIG is explained.

The binary call signal RI arrives at a call switch RU, which is controlled by one in the signal converter SWT of the subscriber device TG formed binary signal SI is controlled.

This binary signal SI, its generation and transmission will be explained below, has the logic value "L" when the loop in the subscriber's telephone set is closed , i.e. with the handset removed. When hung up Handset or when the loop current is interrupted the signal SI has the logical value "0" due to the dial (dialing pulses). Switches in the idle state (SI = O) the call switch RU through the call signal RI to the multiplexer and after picking up the handset (SI = L) instead the 48 kbit / s digital signals supplied by the delta encoder. The ringing signal RI is then sampled by the multiplexer at a frequency of 48 kHz, and the samples are taken as Bit stream with the speed of 48 kbit / s within the bit positions 3 to 8 des provided for the voice channel

Multiplex frame (Fig.2) transmitted to the subscriber.

The loop closure signal SI controls apart from the call switch RU a transistor TrA through which a current flows through the winding of a relay Gv whose relay contact gv is in the exchange-side loop. For SI = L, if there is a loop closure on the participant side, If the relay Gv is energized, the relay contact gv is closed and a loop on the switching side is established via the two-wire winding of the fork. For SI = O falls

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the anchor from Gv, so that the contact gv through the Dial or the hook switch on the subscriber side caused loop interruptions on the Mediation side simulates.

The signal converter SWA of the office device AG also contains a device for charge pulse detection. This converts - similar to the facility for caller identification - those arriving from / for the telephone exchange connected voice subscribers certain charge impulses, which are branched off by a charge pulse switch, in a binary signal GI. GI has the logical value "L" during a charge pulse and the logical value "0" in the pulse pauses. This logic signal GI, which is an asynchronous signal, is then within the Multiplex frame transmitted to the subscriber in the scanning process. For this purpose, the 9th bit parts of the AG Time division multiplex frame transmitted to the subscriber device is used (FIG. 2).

By forming uberframes, this 9th bit can be used for Transmission of charge pulses from several telephone or data channels can be used. With three channels E.g. in the first frame the Gl information of the first channel, that of the second channel is transmitted in the second frame, that of the third channel in the third frame and synchronization information is transmitted in the fourth frame. With a frame repetition frequency of 8 kHz, this means a sampling frequency of 2 kHz for the charge pulse signals GI each

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Canal. The same superframing is for the broadcast the loop closure information SI generated on the subscriber side from several channels is possible. These Loop closure information is also provided at the 9th bit inserted in each multiplex frame that is included in in this case transmitted from the subscriber device to the exchange device will.

The subscriber-side signal converter is described below SWT described with reference to Fig.7. As on the exchange side, a delta encoder and a delta encoder is over a fork transmitter connected to the two-wire loop, in which a conventional telephone set is switched on is. The actual speech signal processing therefore needs not to be explained in more detail.

from the demultiplexer (Fig. 6) receives the signal converter SWT the binary charge pulse signal GI, which except for one slight sampling distortion equal to that in the trunk unit generated signal GI. The clock with the frequency of 48 kHz used for the delta modulation is converted into a divider T1 generates a continuous square wave with a frequency of 16 kHz by dividing the frequency by 3, the in an AND circuit U1 from the charge pulse signal GI is keyed. The resulting 16 kHz pulses are smoothed in a low pass TP and with the help of a charge impulse switch, as it is customary as an official switch on the The two-wire side of the fork is looped into the speech path. In this way, a telephone set with built-in Charge indicators are used.

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On another output line of the demultiplexer (Fig. 6) appears either the binary ringing signal RI or the digital voice signals with 48 kbit / s. This output line leads in the signal converter SWT (Fig. 7) to a call switch, which like the one in the exchange device (Fig. 5) is controlled by the loop closure signal SI. When the loop is open, i.e. when the handset is on the hook, only RI ringing signals arrive, which are then fed to one input of an AND circuit U2. At their other entrance is a clock signal with a frequency of 15.625 Hz, which is in a divider T2, which divides by 1 024, of the 16 kHz clock signal supplied by the divider T1 is derived. This clock signal with a frequency of 15.625 Hz is keyed in the AND circuit U2 by the call signal RI, and the resulting call pulses are in a call device made audible with connected alarm clock.

Finally, there is also the device SSE of the signal converter SWT in the subscriber device, which has already done this several times mentioned loop closure signal SI generated to explain.

The voltage generator shown in Fig. 7 generates at With the power supply switched on, a constant voltage of 10 V between terminals e and f. This voltage only causes a current to flow through the telephone if the hook switch is there (when removing the Handset) closes the loop. This loop current through the subscriber loop flows through the telephone set and one

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Resistor RS and a current limiting device SBG and generates a voltage drop across the resistor RS. These Voltage is applied to the two inputs of a comparator amplifier V applied, which supplies the binary signal SI at its output. When the telephone set is between its two connection terminals are low-resistance, i.e. when the loop closes, SI = 1. If the Loop current, either through the hook switch (hanging up the handset) or through the number switch The loop closure signal SI assumes the logic value 0 (when dialing). This loop closure signal SI, which also represents dialing pulses is now - if necessary with loop closure signals from other channels through Uberframing - from the multiplexer in the 9th bit position the time division multiplex frames sent to the exchange (Fig. 2) inserted.

The power supply of the exchange device AG and the subscriber device TG will be explained below.

Since the power consumption should be zero in the idle state, the power supply of the exchange device and the subscriber device is only switched on with an incoming or outgoing call request or at the same time as a data terminal device and switched off again after the end of the call or after all data terminal equipment has been switched off. The activation The power supply can therefore be carried out by three processes:

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1. Lifting the handset of a telephone set (outgoing call request)

2. Arrival of a 25 Hz ringing pulse in the exchange Signal converter (incoming call request)

3. Switching on a data terminal equipment (DEE or BFS) on the subscriber side.

Are all data terminal equipment on the subscriber side switched off and the handsets of all connected devices are in place Telephone sets at., If there is no new call from the telephone exchange, the power supply automatically switched off after a certain period of time. Those on both sides of the subscriber line to Switching on and switching off the power supply is shown in Fig. 8.

in this figure corresponds to that on the right half illustrated switching-side circuit part of the device designated as "voltage supply" in FIG. and the subscriber-side circuit part shown on the left-hand side with the terminal pairs c-d and e-f corresponds the device designated in FIG. 7 as "switch-on loop and voltage generator".

The positions of the relay contacts shown in Fig. 8 apply for hibernation. In the idle state, the office battery is via one winding WI of a transformer UE and relay contacts s2 and t2 connected to the two-wire line, so that on the subscriber side between the terminals c and d the battery voltage is 60 volts. As can be seen from Figure 7, between the terminals e and f

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the telephone set and data transmission equipment switched. These data transmission facilities are adaptation devices that are assigned to the connected data terminals DEE and BFS in the subscriber device are similar to the signal converters intended for voice transmission. In FIG. 6, these data transmission devices are omitted for the sake of simplicity.

If the hook switch contact of the telephone set is now closed (removing the handset) or one of the If data terminals are switched on, then between e and f - either in the telephone set or within a Data transmission facility - a conductive connection established over the subscriber line and this Connection then flows a direct current, which the relay R

Ί5 in the exchange device and the relay P in the subscriber device energized. Thus, the contact r _f closes whereby a relay T is energized, which then holds itself via a contact ti. In this state, a direct current flows through you between the -60 V terminal of the office battery and earth

Voltage transmitter that provides a constant from this current

Supply voltage of -10 V for the various devices of the exchange device. The energized relay T is In addition, the battery voltage of -60 V is applied to the digital transmitter (Fig. 4) and the digital transmitter and the digital receiver via the switchover contact t2 to the Two-wire subscriber line switched on. With the excitation of the relay P flows through on the subscriber side the remote feed current supplied by the office battery via the contact p1 and the connection AS to the subscriber side

Voltage transmitter providing a constant supply voltage of

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-10 V supplies for the subscriber device. The energized relay P also switches over a contact p2. This will be the terminals connected between terminals e and f (telephone and data transmission equipment D (JE) separated from the two-wire subscriber line and from the voltage transmitter with the constant voltage of -10 V supplied. The remote feed current that flows through the voltage transmitter on the subscriber side in this state, The digital transmitter of the central office device delivers due to the battery voltage of -60 V as direct current with superimposed digital signals.

The power supply of the exchange device AG and the subscriber device can be controlled from the switching side Only switch TG on when a call comes in for a telephone set connected to the subscriber unit.

Switching on the power supply through a call to a data terminal is not provided. Data terminal equipment are activated by the subscriber when he wants to send data (or telex via BFS) or expects to receive data.

So if a call from the telephone exchange FV arrives at a signal converter SWA in the exchange device, then how already mentioned, the 25 Hz ringing pulses are emitted at the output terminals RE of the "call recognition" device (FIG. 5). With the help of the transformer UE, these pulses are reduced to the constant voltage on the switch-on line -60 V superimposed. This means that the first 25 Hz call

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pulse through the winding of the relay R and the changeover contact t ₂ to the two-wire subscriber line, between whose terminals c and d on the subscriber side there is no direct current connection at this time. This 25 Hz pulse, which corresponds to a ringing pulse and thus has a duration of about 1 second, is rectified and smoothed on the subscriber side, so that the resulting direct current pulse causes the relay CT to respond. The now closing contacts cT1 and cT2 allow direct current to flow through the voltage generator and via the connection AS to the two-wire terminal d, whereby the relay P is energized, which holds itself after the armature has dropped from CT via the contact p1, so that the loop on the Participant side remains closed.

The direct current flowing on the line allows not only the subscriber-side relay P but also the switching-side relay R to respond and thus causes the connection of the supply voltage for the exchange device in the manner described above. Before the second 25 Hz ringing pulse appears at the RE terminals, the relay T has _{responded and, with its changeover contact t 2, switched off} the exchange battery and the 25 Hz ringing pulses from the subscriber line. The other call signals now arrive in digital form, as described, from the digital transmitter of the exchange device to the digital receiver of the subscriber device.

As already mentioned, the power supply of the subscriber device and the exchange device is automatically switched off, if all subscriber loops are open and if there is no call to a signal converter in the Exchange device is present. This is practically the case when a certain «

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For a long time the demultiplexer (Fig. 4) only loop closure signals SI with the logical value "O" (loop open) and the caller identification in the signal converter SWA (Fig. 4) only emits call signals RI with the logical value "0" (no call pulse). The switch-off occurs in terms of the circuitry the power supply in the following way:

All loop closure signals SI supplied by the demultiplexer are combined via an OR circuit (not shown) and fed to one input of a NOR circuit N. At the other input is the call signal RI or, in the case of several voice channels, the call signals RI from these voice channels, which are combined in an OR circuit (not shown). When RI = O and SI = O, the output signal AN = RI + SI (+ «" or ") has the logical value ¹¹ L". As long as AN = L, a timing circuit with the input of the signal AN causes an exponential one Rise in the voltage at a relay S, which causes it to respond after reaching a certain value. Then the contact si interrupts the current through the relay winding T, whereby the digital transmitter and the voltage transmitter of the exchange device are separated from the exchange battery Contact t2 the office battery is connected to the subscriber line, a contact s2 is opened, so that the subscriber-side voltage transmitter no longer receives remote feed. After this process, the relay S goes back to the idle state, in which all contacts are in the in Fig.8 are in the positions shown, which can then be switched on again immediately.

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Claims (8)

STANDARD ELECTRICS LORENZ SHARED COMPANY STUTTGART W. Kaiser-H.T. Hagmeyer 14-1 Claims ^ 1. ^; System for multiple use of a two-wire subscriber line in the telephone switching network with an exchange device and a subscriber device fed via this remote control, characterized ; that for the transmission of speech from at least one speech channel and / or data from at least one data channel, each of the two devices (AG, TG) contains the following assemblies - A signal converter (SWA, SWT) for each voice channel, which converts the analog signals from this voice channel into converts digital signals and the digital signals back into analog signals, - A multiplexer, the over the two-wire subscriber line data signals to be transmitted from the connected data channels and the digitized ones Combines signals from the connected voice channels into a time division multiplex frame (Fig. 2), - A circuit arrangement for direction separation which controls a time- alternating transmission of message blocks in the two transmission directions of the two-wire subscriber line (FIG. 3) and CS / P-Kg / Sch
11/17/1977 90982B / 0A84 27 b 8 VOS W. Kaiser 14-1 - a demultiplexer for dividing the received time division multiplex frames into the individual channels, and that the exchange device (AG) to the telephone exchange (FV) for voice transmission and to the data exchange (DV) is connected for data transmission, the connecting lines between the central office device (AG) and the Telephone exchange (FV) and between the exchange device (AG) and the data exchange (DV) to the subscriber device (TG) are permanently assigned to connected voice and data channels. 2. System according to claim 1, characterized in that each message block contains exactly one time division multiplex frame (24 bits, Fig.2). 3. System according to claim 1, characterized in that each message block contains an integral multiple of a time division multiplex frame. 4. System according to one of claims 1 to 3, characterized in that the time division multiplex frame (Fig. 2) formed in the multiplexer of the office device (AG, Fig. 2) apart from the bits for the digital voice and data signals, at least one bit (no. 9) for the transmission of charge pulses (GI) from the exchange to the subscriber. 5. System according to one of claims 1 to 3, characterized in that the time division multiplex frame (Fig. 2) formed in the multiplexer of the subscriber device (TG, Fig. 6) apart from the bits for the digital voice and data signals has at least one bit (no. 9) for the transmission of information (SI) via the loop closure in the subscriber-side terminals, in particular of dialing pulses from telephone sets, to the exchange device (AG). 909826/0 ^ 84 W. Kaiser 14-1 6. System according to one of the preceding claims, characterized in that the exchange device (AG, Fig. 4) and the subscriber device (TG, Fig. 6) each contain a transmitter which encodes the digital signals to be transmitted without direct current on the two-wire Subscriber line flowing remote feed current superimposed. 7. System according to one of the preceding claims, characterized in that in the office device (AG) and in the subscriber device (TG) relay devices (Fig.8) are provided, which switch on the remote feed current and the power supply of the office device (AG) only when either one of the subscriber-side data terminal equipment (DEE, BFS, Fig.1) is switched on, or if a call arrives in the telephone exchange (FV) for a telephone set connected to the subscriber device (AG) or if there is a loop in a telephone set. 8. System according to one of the preceding claims, characterized in that a clock generator controllable by the clock of the data exchange and in the subscriber device (TG, Fig.6) a circuit arrangement for clock recovery from the received signals is present for clock supply in the exchange device (AG, Fig.4) . 909826/048 *