AU649363B2 - A process for checking the operability of transmission circuits for communications signals - Google Patents

Abstract

A method is described for testing the operation of transmission links for telecommunications signals in a telephone network, with which the signals of an exchange are fed in as analog signals, are transmitted in a data stream as digital signals between a system unit of the exchange and at least one subscriber and are fed once more as analog signals at the subscriber end from a system unit of the subscriber to a terminal of the subscriber. A transformer with a hybrid circuit, and also A/D converters, a control block and a line codec are provided in both system units between the analog and digital interfaces. A transmitter and a receiver for digital signals are connected in the control block of at least one of the system units to the transmission link of one transmission direction. When the link is checked and an associated activation of the transmitter performed, the transmission link for the data stream of the digital signals is interrupted and at least the hybrid circuit of the system unit whose transmitter is activated is simultaneously disconnected from the analog interface.

Description

S F Ref: 217526

AUSTRALIA

PATENTS ACT 1990 4 9 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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*r p Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: ke Kommunikations-Elektronik GmbH Co Kabelkamp 3000 Hannover 1

GERMANY

Thomas Bratschke, Martin Brahms, Wolfgang Fritz and Andreas Timmermann Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia A Process for Checking the Operability of Transmission Circuits for Communications Signals .44441 4 4 444444 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845/6 TECHNICAL FIELD The Invention relates to a process for checking the operability of transmission circuits for communications signals In a telephone network, wherewith the signals are inputted as analog signals to a switching centre, transmitted as digital signals in a data stream between a system unit of the switching centre and at least one subscriber, and, at the subscriber, passed as analog signals to a peripheral unit of the subscriber, and wherein a transformer with a branching circuit, analog/digital converters, a control block, and a circuit encoder/decoder are used between the analog and the digital interface in the two system units (DE..Z "PKI Techn. Mitt.

1/1988," pp. 35 BACKGROUND OF THE INVENTION Digital transmission processes facilitate the multiple use of existing transmission circuits by means of time-division multiplexing.

For example, in PCM30 systems, 30 voice signals, Including signalling, are combined into a 2 Mbit/sec data stream. The PCM2 technique described in the above-cited DE-Z "PKI Techn. Mitt." is an other digital transmission process. With these known processes, two PCM channels can be transmitted via a double line. To this end, the analog voice signals are digitized in 20 a switching centre of the telephone network, transmitted via the double line, and converted into analog voice signals at the termination of the transmission circuit.

The operability of such transmission circuits and of the equipment and circuits employed therein must be guaranteed like the operability of the entire telephone network.

SUMMARY OF THE INVENTION ":000 The problem underlying the invention Is to develop the above-specified process so that the operability of the digital transmission circuit can be checked In a simple manner.

30 According to the Invention, this problem Is solved by connecting, in the control block of at least one of the system units, a transmitter and a receiver for digital signals to the transmission path in the one direction of transmission, and interrupting the transmission path for the data stream of digital signals upon activation of the transmitter and, at the same time, separating, from the analog interface, at least the branching circuit of that system unit whose transmitter is activated.

The transmitter provided In the control block is switched on when the 738z/jrb -1operability of the digital transmission circuit Including the system units or the operability of one of the system units proper or of parts of the circuitry of the same are to be checked. The transmission path for the digital signals is interrupted at the same time so that only the digital signals emitted by the transmitter pass to the receiver. The data stream can be interrupted by, say, a digital multiplexer. The digital signal generated by the transmitter is inputted into, say, an a/d converter and is passed therefrom to the branching circuit as an analog signal. The branching circuit is detuned due to its separation from the analog interface so that the arriving analog signal of the transmitter is reflected and enters the outgoing branch of the branching circuit. It is reconverted into a digital signal by the a/d converter inserted into this transmission path and runs through the control block and the circuit encoder/decoder of the proper system unit, the transmission path, the system unit at the far end, and once more the transmission path. When the transmission path is undisturbed, the digital signal reaches the receiver via the proper circuit encoder/decoder. When the signal arrives at the r. receiver in a specified time of, say, 2 msec and is recognized as a signal emitted by the transmitter, the transmission path through which the signal 20 passed is operative.

This process can be practised in a particularly simple way and with low expenses. Both transmitter and receiver can be integrated in the control block which is anyhow present and which may be, for example, a silicon chip. In the same there is, for example, a gate array.

Transmitter and receiver are provided on the silicon chip preferably as early as when the silicon chip is produced.

Advantageous embodiments of the invention are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS 30 The process according to the invention is explained as an embodiment with reference to the drawings.

There show: Figure 1, in a schematic representation, the termination of the transmission path of communications signals; Figure 2, a detail of Figure 1 in an enlarged representation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 shows diagrammatically a circuit for a PCM2 system with which twQ subscribers T1 and T2 can be connected with equal priority to the 738z/jrb -2telephone network via a line L In the form of a double wire. To this end, analog signals from the telephone network are through connecting lines inputted to a switching centre VST or vice versa. Only two of these lines are indicated in Figure 1.

The signals are passed from the switching centre VST via the analog interface a/b into a system unit VA the output of which is formed by the digital interface U. The signals, which were digitized in the system unit, are transmitted via line L to a system unit TA which is associated with one of the two subscribers T1 and T2 and at the analog interface a/b of which there appear analog signals. The analog signals are inputted into the peripheral units of subscribers T1 and T2, Into telephones.

System units VA and TA comprise components and circuits which, in the embodiment illustrated, are suitable for connecting two transmission channels for the two subscribers T1 and T2. These are basically A/D converters and a transmission unit U which together form a system SY required for a subscriber and indicated by broken lines for the system unit VA. When only one subscriber Is connected to the switching centre VST or the line L, only one such system Is required in system units VA and TA.

The system SY them forms the system unit VA or TA. If there are more than 20 two subscribers, more than two systems SY are needed. In the well-known PCM4 technique, where four subscribers are connected to the line L, four systems SY are used.

Such a system SY is shown in greater detail and on an enlarged scale In Figure 2 ire only the parts or circuits and components required for understanding the Invention are indicated: A transformer 1, which Is connecred with a branching circuit 2, Is connected to the analog interface a/b. Two separate transmission paths extend from branching circuit 2, one path for each of the directions of transmission, with A/D converters 3 and 4 inserted therein. A control S block 5 and a circuit encoder/decoder 6 are associated with the two transmission paths. The circuit encoder/decoder 6 is connected with the digital interface U to which the line L is connected.

Control, block 5 is an intelligent module controlling all functions within the system SY. This is, for example, a gate array in which digital circuits are combined on a silicon chip to perform logic functions and/or operations- The digital signals from A/D converter 3 are shaped in control block 5 and encoded in a line-compatible code in the circuit encoder/decoder 6.

738z/jrb -3- In addition to the components required for transmitting signals, control block 5 comprises a transmitter S and a receiver E. When switched on, the transmitter emits digital signals, for example, certain bit patterns. The signals are to be chosen so that the corresponding analog signal is in the audio range, specifically in the range between 300 Hz and 3400 Hz. Transmitter S and receiver E can be connected, or are connected, with the one transmission path which, between transmitter S and receiver E, can be interrupted by a switch 7. Switch 7 is indicated only symbolically. In a preferred embodiment, it is formed by a multiplexer or a digital multiplexer.

In the line to transformer 1, between the analog interface a/b and the transformer 1 there is a switch 8 which can be configured as, say, a transistor. Switch 8 could also be inserted between the transformer 1 and the branching circuit 2. When switch 8 is open, the branching circuit 2 is disconnected from the analog interface a/b.

The process according to the invention functions, for example, as 1 follows: When the operability of the "far" loop between the two analog interfaces a/b of the switching centre VST, on the one hand, and the 20 subscribers Tl ani T2, on the other, is to be checked for a subscriber, then, for example, the transmittr S of the system SY of system unit VA is switched on. At the same time, the transmission path for the data stream of the digital signals Is interrupted (switch 7) and the switch 8 is opened.

The digital signal emitted by transmitter S is applied to the A/D converter 4. It is converted by the same into an analog audio signal reflected by branching circuit 2 which Is detuned because of the opened 0:000i switch 8. The reflected signal passes to A/D converter 3 by which is is reconverted into a digital signal. Thereafter the digital signal passes through control block 5 and the circuit encoder/decoder 6. The signal is 0*6 30 inputted into line L at the interface U. At the far end, the signal passes through the system SY of the local system unit TA comprising a circuit encoder/decoder, control block, A/D converters, and detuned branching circuit and is inputted into receiver E via line L and the own circuit encoder/decoder 6. There, as the case may be, the digital signal is recognized as a signal of the transmitter S. The important point is that the signal is received within a predetermined time of, say, 2 msec.

Each system SY of the system units VA and TA can have the described transmitter/receiver combination In its control block 5. But It is also 738z/jrb -4possible to provide in each system unit VA or TA only one transmitter/receiver combination which can be switched to the respective subscriber. This can be effected preferably by time-division multiplex operation. Checking a subscriber may be initiated, by depressing a button, either in the switching centre VST or at the subscribers Tl and T2. In the preferred embodiment, the transmitter-receiver combination is provided only in the system unit VA of the switching centre VST because checking the transmission paths is In almost all cases effected from that point. In this case it must be ensured that, upon activating the transmitter S, the branching circoits of the system unit TA are optionally (far loop) disconnected from the analog interface a/b.

When the signal of transmitter S does not appear at receiver E within the preset time or not at all, the transmission path is malfunctioning.

For easy localization of a corresponding failure, the signal emitted from transmitter S in system SY can be sent in a "local" loop to the receiver E via a connecting line 9 within the control block 5. In this way it Is possible to establish whether the local A/D converters 3 and 4, the branching circuit 2, and the control block 5 are operative. For this purpose, the receiver E can be switched to the second transmission path by 20 means of a commutator 10. In this case, the branching circuits 2 of the respective other system unit VA or TA need not be disconnected from the analog interface a/b.

In principle, transmitter S, receiver E, and switch 7 can be connected to the other transmission path In control block The process can also be used when, in addition, a code conversion, with the ADPCM process, is carried out in system units VA and TA.

0*99** 9 9oe 738z/jrb

Claims (4)

1. A process for checking the operability of transmission circuits for communications signals in a telephone network, wherewith the signals are inputted as analog signals to a switching centre, transmitted as digital signals in a data stream between a system unit of the switching centre and at least one subscriber, and, at the subscriber, passed as analog signals to a peripheral unit of the subscriber, and wherein a transformer with a branching circuit, analog/digital converters, a control block, and a circuit encoder/de- coder are used between the analog and the digital interface in the two system units, characterized in that in the control block of at least one of the system units, a transmitter and a receiver for digital signals are connected to the transmission path In the one direction of transmission, and the transmission path for the data stream of digital signals Is interrupted upon activation of the transmitter and, at the same time, at least the branching circuit of the system unit whose transmitter is activated is separated from the analog interface

2. The process according to Claim 1, characterized in that with two or more S subscribers (Tl, T2), for each subscriber in the control block there Is connected a transmitter/receiver combination to the one transmission path.

3. The process according to Claim 1 or 2, characterized in that the same transmitter/receiver combination, adapted to be switched on by time-division multiplexing operation, is used for all subscribers (T1, T2).

4. The process according to any one of Claims 1 through 3, characterized in that in the control block there Is arranged an additional connecting line connecting with the receiver that communication path to which the emitter and the receiver are not connected when the branching circuit of the system unit with the activated transmitter is disconnected from the analog interface. The process according to any one of Claims 1 through 3, characterized In that the branching circuits of the two system units are disconnected from the analog interface when a transmitter is activated. DATED this NINTH day of DECEMBER 1992 ke Kommunikations-rlektronik GmbH Co Patent Attorneys for the Applicant SPRUSON FERGUSON 738z/jrb -6- A Process for Checking the Operability of Transmission Circuits for Communications Signals Abstract Tho described a process for checking the operability of transmission circuits for communications signals in a telephone network, wherewith the signals are inputted as analog signals Into a switching centre (VST), transmitted as digital siganls in a data stream between a system unit (VA) of the switching centre and at least one subscriber, and, at the subscriber, passed as analog signals to a peripheral unit (TA) of the subscriber. In the two units (VA, TA), a transformer (1) with a branching circuit analog/digital converters a control block and a circuit encoder/decoder are inserted between the analog and the digital interface. In the control block of at least one of the units (VA, TA), a transmitter and a receiver for digital signals are connected to the transmission path in the one direction of transmission. When the transmission path is checked and, hence, the transmitter is activated, the transmission path for the data stream or digital signals is interrupted and, at the same time, at least the branching circuit of that unit (VA, TA) whose transmitter 20 is activated is separated from the analog interface Figures 1 and 2 9 KRS/9940T