DE3007766A1 - Telephone subscriber station - has standard two wire link to analogue exchange plant and optional bidirectional digital speech processor - Google Patents

Abstract

In order to provide the subscriber of a standard speech channel telephone terminal having traditional two-wire link to the analogue exchange station (A-Vst) with the option to communicate also with digital stations, the circuit associates the four-wire microphone (M) and audio transducer (H) terminals with the usual analogue gating circuit (AG) for transference to the two-wire line (NSW-Al) and, furthermore, with changeover switches (U2, UM, UH) responsive to a control voltage level (u) which when switched applies the four terminal wires to another, digital, gating circuit (D2V) comprising a speech encoder circuit (CO) and digital transmitter (DS) on the one hand, and a speech decoder circuit (DEC) and digital receiver (DE) on the other hand. To avoid mutual interference of the incoming and outgoing digit signals the two channels are allocated different time slots, or differently weighted frequency ranges. Normally the telephone set may be connected via the analogue 2 to 4 line gating circuit (AG). Upon detection of a high-bit rate signal, a control voltage (u) is generated which automatically switches to the digital/analogue gating and processor unit (D2V). Alternatively, a change-over switch (BU) may be used.

Description

To a two-wire exchange via a two-

wire connection line connectable telecommunication subscriber station.

Recent developments in telecommunications technology lead to digital telecommunications systems, the conversion of the voice signals into digital signals for telephone users (and vice versa) already provided in the subscriber station and in those via digital four-wire exchanges Digital telephone connections in standardized communication channels with a Bit rate of preferably 64 kbit / s (per transmission direction) can be built up. Except Speech can also transmit texts, data and images in the 64 kbit / s standard channels will; such a transmission and switching (transmission) of digital signals in 64-kbit / s standard channels, in which, for example, telephony and faxing, for example into two corresponding 32 kbit / s subchannels carrying signals of a 64 kbit / s standard channel can take place (3E-AS 27 29 689), is integrated in a future service Telecommunications network (ISDN) to be expected.

Presently and in the near future, however, both local switching as well as for private branch exchanges that are still used today in the analog telephone network customary two-wire exchanges are used, to which two-wire connecting lines each with a signaling circuit located in the two-wire branch and one the two-wire branch into a four-wire speech current / hearing current branch analogue telephone subscriber stations provided with the transferring analog signal hybrid circuit are connected. With the introduction and further completion of a service-integrated Digital network is therefore already a large number of such telecommunication systems in the context the conventional analog telecommunications network be in operation; but still have the advantages To be able to use digital communication methods, the invention shows a Path.

In this context it is already known (from DE-OS 28 28 583) in a communication system using the conventional analog network Digital network is superimposed, which with digital terminal exchanges and digital Subscriber stations is equipped, subscriber stations each to both the analog network as well as to be connected to the digital network and switchable between the two networks close. Such a connection of subscribers make at two different exchanges However, two different telecommunications networks require a corresponding effort on connecting lines and also specifies the presence or accessibility a corresponding Digital exchange next to an analog exchange in advance.

Starting from one to a two-wire exchange via a Two-wire connection line connectable analog telecommunication subscriber station with a signaling circuit located in the two-wire branch and one in the two-wire branch in a four-wire send / receive branch, especially voice power / Mörstrom branch line, transferring analog signal hybrid circuit now arises the invention the task of interested in the advantages of digital communication methods To offer subscribers of the conventional analog telecommunications network a subscriber station, which, without having to be connected to two different exchanges, in addition to conventional analog operation, optionally also in a single digital communication channel Digital operation enables. According to the invention, this is done in a telecommunications subscriber station of the type outlined above parallel to the analog signal fork circuit a means Switching devices instead of the analog signal hybrid circuit between the two-wire branch and digital signal two-wire / four-wire circuit insertable into the four-wire transmission / reception line branch with upstream voice signal coder on the transmit side and downstream on the receive side Speech signal decoder provided.

The invention, which is the broadband capability of the crosspoint switch the two-wire exchanges commonly used today and the two-wire local connection lines installed today makes use of, it also allows the subscriber line circuits, as it is given with so-called choke feed, also in a conventional analog telecommunications network while continuing to use the signaling and connection setup and connection that are customary therein dismantling procedures and the other switching-related performance features, i.e. within the scope of existing two-wire exchanges and private branch exchanges, the advantages of digital communication methods, such as extensive attenuation independence, constant and possibly improved speech quality and easier implementation of various Forms of communication in an existing connection (mixed communication) and Realizability of additional performance features to be able to use. Advantageous is the avoidance of compatibility problems in connection with the existing ones Analog telecommunication subscriber stations: From one in the specified manner between Analog operation and digital operation switchable telecommunication subscriber station are on the one hand Analog connections both to pure analog subscriber stations and to additional ones subscriber stations equipped in the specified manner with a digital operating circuit possible and on the other hand digital connections both to pure digital subscriber stations as well as to subscriber stations only additionally equipped with the digital operating circuit, with which the possibility is given, if necessary, only individual participant positions conventional local exchange or private branch exchange in the specified Way to equip for an additional digital operation.

In an expedient embodiment of the invention, the switching devices can by manual signaling and / or in accordance with the receipt of digital signals be switchable; this allows one of one to work in digital mode Subscriber station incoming call, the traffic is automatically handled in digital mode while it remains in analog mode if one of the two subscriber stations is a pure analog subscriber or wants to work in analog mode.

The digital signal expediently has a two-wire / four-wire circuit a hybrid circuit for separating the digital signals of the two transmission directions on; in a further embodiment of the invention, however, instead or in addition for this purpose a digital signal transmission circuit for sending out transmission signal pulses specific times or with a given focus of their frequency spectrum and a digital signal receiving circuit for receiving received signal pulses at other times or with a different focus of their frequency spectrum be provided.

Appropriately, in a further embodiment of the invention, the Subscriber station have a free-running clock generator. A central clock supply from the exchange is then not required; at the same time is also omitted a synchronization in the switching center itself: the switching center can the digital signals running asynchronously in both transmission directions are two-wire switch through, just as it has previously switched through audio-frequency voice signals.

In a further embodiment of the invention, the speech signal coder by a delta modulator and the speech signal decoder by a delta demodulator be given; this brings particularly high voice quality (with a given bandwidth) and insensitivity to bit errors with it. Meanwhile, the invention is not limited to delta modulation; in principle, other types of modulation are also such as.

Pulse code modulation, possible.

To in addition to a transmission of digital voice signals also Transmit texts, data and / or images using appropriate digital signals to be able to use the digital signal transmission circuit and the digital signal reception circuit expediently also corresponding data device connections.

The invention will be explained in more detail with reference to the drawing.

The drawing shows schematically in one for understanding the invention required scope of a telecommunications system with a subscriber station according to Invention.

This telecommunications system is connected to a (e.g. through a private branch exchange ESK 10/2 electronic or EMS 300 given) two-wire exchange A-VSt the two-wire connection lines not shown in detail in the drawing Analog telephone subscriber stations each with one in the two-wire branch lying signaling circuit and one the two-wire branch in one four-wire speech current / audio current branch connecting analog signal hybrid circuit can be connected via a Two-wire connection cable Al a telephone subscriber station Tln connected, the one in the two-wire branch As - NSW lying signaling circuit NSW and one the two-wire branch Al - NSW into a four-wire speech / hearing current branch A-M / -H Has analog signal hybrid circuit AG. In the drawing it is indicated that the signaling circuit NSW by a conventional number switch / alarm clock circuit and the analog signal hybrid circuit AG by a conventional transmitter bridge circuit can be formed. This allows the telephone subscriber station Tln (in the Switching state of the analog signal hybrid circuit AG shown in the drawing the two-wire branch NSW - Al or the four-wire branch M, H Switching devices UZ, UM, UH) with the delivery of dialing impulses or

Receipt of soot current signals when establishing a connection, transmission of Analog voice signals while a connection is established and loop current interruption Participate in telephone traffic in the normal way when the connection is released (Analog operation).

In the telephone subscriber station Tln is now parallel to the analog signal hybrid circuit AG a digital signal two-wire / four-wire circuit DZV with upstream, e.g. speech signal coder CO given by a delta or pulse code modulator and downstream on the receiving side, possibly by a delta or pulse code demodulator given speech signal decoder DEC is provided. This circuit is by means of the already mentioned switching devices UZ, UM, UH instead of the analog signal fork switch AG between the two-wire branch Al - NSW and the four-wire speech current / Hearing current branch M, H can be inserted, including the switching devices UZ, UM, UH at control inputs u to one Operation of an operating mode switch BU corresponding switchover signals may be supplied. After such a switchover the telephone subscriber station Tln can continue to use the usual signaling procedures to participate in connection establishment and termination; the actual telephone traffic is now, however, with the transmission of, for example, 64 kbit / s digital telephone signals handled (digital operation), with the digital circuit branch possibly also providing the holding current the loop for remote power supply.

When the digital signals are transmitted using the synchronous method, the digital signal two-wire / four-wire circuit DZV for decoupling transmission and Received signals have a hybrid circuit (bridge circuit) DG, which is used to achieve a sufficiently high fork lock attenuation, so that the transmit digital signals at the received digital signals cannot cause any bit errors, a very exact one Must have simulation of the input impedance of the two-wire connecting line Al.

If necessary, analog signal hybrid AG and digital signal hybrid DG also coincide with each other, so that the same hybrid circuit in both modes of operation is used, with a deviation from the relationships shown in the drawing to design the UZ switching device four-wire and in the four-wire branch A would be to be arranged. In the case of a compromise replica that is often provided in practice, with which one tries to take into account different line impedances, can to improve fork lock damping, for example (e.g. according to electrical communications 53 (1978) 2; 118 ... .121) an automatic adjustment of the line simulation or (e.g. according to FREQUENCY 28 (197L) 5, 118 ... 122 and 155 ... 161, 121) a compensation of the Interfering signals be provided in the receiving branch of the hybrid circuit.

The transmission signal pulses can thereby, without this being shown in the drawing is shown in more detail, occur with a send bit clock that is from one in the subscriber station contained, freely oscillating clock generator is generated.

The digital signals are used to decouple transmit and receive signals on the two-wire connecting line Al in the separation process by one for the two directions of transmission (e.g. according to DE-AS 23 46 984 or DE-OS 25 11 619) in time or (e.g.

according to DE-OS 27 13 854) in the frequency position separate transmission channels provides, then in the digital satellite two-wire / four-wire circuit DZV a Digital signal transmission hold DS for sending out transmission signal pulses to certain Points in time or; with a given focus of their frequency spectrum and a digital signal receiving circuit DE for receiving ElIrpfangssignalimputsen at other times or with a different focus of their frequency spectrum be provided. It is also possible to use a hybrid DG with a time or Combine frequency separation circuit DS, DE, as shown in the drawing is indicated. The digital signal hybrid circuit DG is a chain circuit here on the transmission side the speech signal coder CO and preferably given by a delta modulator a digital signal transmission circuit DS for transmitting transmission signal pulses, for example upstream at certain times and a chain connection on the receiving side a corresponding digital signal receiving circuit DE and preferably through a delta demodulator given speech signal decoder DEC connected downstream.

The digital signal transmission circuit DS can, for example, pseudo-ternary half-step signal pulses, so-called half-bauded AMI (alternate-mark-inversion) signal impulses, for what purpose they, as suggested elsewhere (DE-P 29 16 576), an instantaneous value of the transmitted signal pulses encoded and stored in accordance with the speech signal coder CO output digital signals can have controlled read-only memory, the sends the corresponding instantaneous values in their coded representation to a decoder, which forms the corresponding transmission signal pulses from it. The digital signal receiving circuit DE can contain a regenerator, as it is in principle (for example from the Siemens publication "PCM - Pulse code modulation and its application in telecommunications", Page 15, Fig. 21) is known and in which with the help of a clock extractor from the Received signal pulses of the received bit clock is derived, due to which the Decision times are defined in which in the digital signal receiving circuit DE in each case the amplitude decision on the respective state value of the relevant Bits is hit; furthermore, the digital signal receiving circuit may have a in the example with a rectifier circuit to be implemented received signal converter which converts the regenerated signals into corresponding AM resp.

Converts PCM signals. The transmission bit clock can, as was done elsewhere (DE-P 29 21 019) is proposed derived from the receive bit clock and compared to this be out of phase by half a bit period. More details regarding one according to the drawing in the digital signal two-wire / four-wire circuit DZV contained digital signal transmission circuit DS and receiving circuit DE need here however not to be explained, since this is not necessary for an understanding of the invention is.

The same also applies to a different type of training Digital signal transmission circuit DS resp.

-Receiving circuit DE amounts to other ways to be reached Decoupling of transmit and receive signals.

In the telephone subscriber station Tln can, as already explained, the switching of the switching devices UZ, UM, UH from analog operation to digital operation (and vice versa) through manual signaling by means of an operating mode switch BU are triggered. In addition, however, it is also possible to use the switching devices in accordance with the reception of digital signals via the two-wire connection line Al to switch automatically.

In the drawing it is indicated that the digital signal receiving device DE via an additional switch UU also in the analog operating state of the subscriber station Tln can be connected to the two-wire branch and that at the same time with the Digital signal receiving circuit DE connected to a level monitoring circuit PÜ which responds when digital signal pulses are received and a corresponding one Outputs control signal, the control signal output of the level monitoring circuit PU combined with that of the operating mode switch BU via an OR element leads to the control inputs u of the switching devices UZ, UM, UH, UU. The level monitoring circuit PÜ is expediently designed so that on the one hand a passing No occurrence of digital signal pulses, as is the case during an undisturbed call connection can occur, is bridged and, on the other hand, in the event of a prolonged failure of digital signals it is switched back to analog operation due to transmission errors - which can also be done manually at any time with the help of the BU operating mode switch can happen.

Finally, it should be noted that the digital signal transmission circuit DS and the digital signal receiving circuit DE additional data device connections gas, gae, to which a modem can optionally be connected, with whose help texts, data or images can also be transferred.

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Claims (7)

Claims 1. To a two-wire exchange via a Two-wire connection line connectable analog telecommunication subscriber station with one signaling circuit located in the two-wire branch and one in the two-wire branch in a four-wire transmit / receive line branch, in particular speech current / hearing current line branch, transferring analog signal hybrid circuit, characterized in that parallel to the analog signal hybrid circuit (AG) one by means of switching devices (UZ, UM, UH) instead of the analog signal hybrid circuit (AG) between the two-wire branch (Al - NSW) and the four-wire send / receive branch (also) insertable Digital signal two-wire / four-wire circuit (DZV) with upstream Speech signal coder (CO) and speech signal decoder on the receiving side (DEC) is provided. 2. Telecommunication subscriber station according to claim 1, characterized in that da3 the digital signal two-wire / four-wire circuit (DZV) a hybrid circuit DG has. 3. Telecommunication subscriber station according to claim 1 or 2, characterized in that that the digital signal two-wire / four-wire circuit (DZV) is a digital signal transmission circuit (DS) for sending out transmission signal pulses at certain times or with a predetermined focus of their frequency spectrum and a digital signal receiving circuit (DE) for receiving received signal pulses at other times or with a has another focus of their frequency spectrum. 4. Telecommunication subscriber station according to one of claims 1 to 3, characterized characterized in that a freely oscillating clock generator is provided. 5. Telecommunication subscriber station according to one of claims 1 to 4, characterized characterized in that the switching devices (UZ, UM, 'WH) by manual signaling and / or can be switched over according to the reception of digital signals. 6. Telecommunication subscriber station according to one of claims 1 to 5, characterized characterized in that the speech signal coder (CO) by a delta modulator and the speech signal decoder (DEC) by a. Delta demodulator are given. 7. Telecommunication subscriber station according to one of the preceding claims, characterized in that digital signal transmission circuit (DS) and digital signal reception circuit (DE) also have data device connections (gas, gae).