DE3044401C2 - Procedure for monitoring and locating faults in PCM transmission systems - Google Patents

Description

The invention relates to a method for monitoring and locating faults in PCM transmission systems according to the preamble of claim 1.

From the article: "In service error-rate detection at dependent repeaters using mark parity control", in CCITT, August 1977, Questions: 4, 11, 13 / XVIII, 10 / IV, COM XVIII-No. 59-E, COM IV-NO. 34-E, a method is known, d-js with character-pantäts-control is working. File's character parity is defined as even if the number of characters is between two certain moments of time. The period of time between two specific moments in time can be constant or variable. A bistable circuit is required for fault detection in an amplifier. Just character parity control in a transmitter causes the bistable circuit in every moment of time is in a certain state. Over the period of time, which includes many specific moments of time, a direct current component occurs at the output of the bistable circuit. This DC component only alternates if there is an error or an odd number of errors in the interval between two adjacent moments in time occurred. This is so because the output of the bistable circuit is in the next Instantly changes to its other state after an error. This new state is now that new normal state. The output of the bistable circuit now has a different direct current component. The change between two levels thus indicates an error. It turns out to be disadvantageous that only an appropriate code can be used.

From DE-OS 25 27 593 a method and a device for remote monitoring of pulse regenerators known, which is specially designed for regenerators that are only effective in one direction. It will superimposed a very low frequency subsystem, in which a frame is used that is at least so has many channels as there are regenerators in the connecting line. The already measured one The error rate is coded and written into the channel assigned to each regenerator and transferred to the receiving channel Head position decoded and displayed. Each beginning of a frame is through a frame lock word characterized, which identifies the regenerator from which the low-frequency carrier frequency was sent out. Falls e.g. B. the i-th regenerator off, then the i + l-th regenerator sends the low frequency Carrier frequency and a frame lock word out because it doesn't receive them and you can out

recognize the relevant rank of the regenerator that the regenerator in front of it is disturbed.

From US-PS 37 60 127 is a system for remote monitoring known from multi-channel PCM regenerators, in which the processors contained in the regenerators are all connected to a service line, at the end of which in terminal A the control unit is located. So it is not a subordinate system.

DE-AS 12 91 781 discloses a monitoring device for a transmission system with pulse modulation known, in which in each intermediate point an oscillator with a specific frequency outside the Frequency spectrum of the pulse modulation to be transmitted lies. If an intermediate point fails, the Oscillator locked so that it is recognized at the terminal due to the lack of characteristic frequency which intermediate point is disturbed.

In the Siemens magazine 49, 1975, issue 7, pages 461-4Ö5, there is a fault location on PCM transmission links described, which relates to an interrupted loop order.

The invention is based on the object of providing a method that is as generally applicable as possible and bit error monitoring and to indicate the fault location of PCM transmission systems that the bit error monitoring allowed during operation, including the location of temporary errors during the Operation is possible. The fault location in the event of a total failure should also be possible with the same method, The monitoring should be based on basic sections, d. H. Extend over several remote feed sections and monitor both terminals be possible from a basic line, without the use of additional cores for error reporting.

The object is achieved by the features specified in the characterizing part of claim 1.

The subclaims specify advantageous configurations.

In the following, the invention will be explained in more detail with reference to an exemplary embodiment by means of figures.

Fig. 1 shows a monitoring section, where mean

1 terminal 1,

2 remotely powered intermediate regenerators,

3 remotely powered intermediate regenerators with remote feed termination,

4 remote-fed intermediate point,

5 end point 2.

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Fig. 2 shows a loop circuit of the monitoring or localization circle, mean

6 locating switch,

7 monitoring terminal,

8 remote feeder,

9 Repeater direction 1,

10 Repeater direction 2,

11 attenuating through-connection in the event of detection,

12 remote feed termination,

13 non-monitoring terminal,

14 damping switching in normal operation,

15 monitoring amplifiers.

Fig. 3 shows a basic circuit of the remotely fed intermediate regenerator, mean

11 Loop closure, which is always on the remote-fed office must be on the opposite side. Switching and relays are not shown here.

15 monitoring amplifiers,

16 phase comparator,

17 oscillator,

18 counters,

19 AND gate,

20 coupling,

21 rectifiers,

22 main meters,

23 decoders,

24 OR gates.

4 shows the overall framework of a query telegram.

Figure 5 shows a single time slot.

The monitoring system according to the invention is superimposed on the actual PCM transmission system, with the formation of monitoring sections which, during normal operation of the PCM main line, are carried out by a End point to the other end point of a base line, with monitoring during the "undisturbed" Operation should optionally be possible from any above-ground amplifier point and monitoring in the event of a »cable break« or »main system error« (»total failure«) automatically to the Section from the end point or the associated remote-feeding amplifier point to the point of failure or the following remote feed termination is limited to enable fault location (see. Fig. 1). By Special measures are taken to ensure that localization is possible even in the event of errors in the monitoring system is.

Monitoring is possible from both end points of a base line. This requires the transfer the feedback signals via remote feeder terminals and remote feed repeaters in both directions.

For monitoring in the event of a total failure (cable break), the loop closure circuit closes both the Fernijjeise loop like the fault location loop. Therefore the loop closure circuit for the feedback signals create a low-frequency cross connection with appropriate attenuation between the two transmission directions. This cross-connection can optionally in a particularly advantageous manner through the loop termination resistance alone without additional HF connection can be achieved.

In the event of failures in the monitoring system that do not occur at the same time as failures of the operating system, e.g. B. by amplifier failure, it is still possible to locate the fault location <: s by lowering the level of the Te ^u .rr * iriesignals in a defined manner. The telemetry devices from the point of failure then no longer respond. However, an evaluation can still take place in the end station.

The monitoring in the repeaters can be used for systems with different line codes, z. B. for 140 Moit and 565 Mbit systems.

For example, in the 140 Mbit system with MMS 43 line code, monitoring is expedient of code rule violations by evaluating the exceeding of the limit values by the current digital sum of the signal in the output stages. Errors found are indicated by the following Counting circuits are added up and a memory is set if one or both counting circuits overflow.

When the repeater is queried, the memory content is output as well as memory and counting circuits reset.

In the 565 Mbit system with AMI line code z. B. the error measurement by evaluating the AMI code rule violations, d. H. with successively identical amplitudes. Since in every repeater the AMI signal is newly formed, code rule violations are made not passed on and in each repeater only those in the previous amplifier field character errors occurred measured.

The system's own low-frequency four-wire auxiliary system, which is used for control and reporting purposes subordinate to the actual PCM transmission system. This auxiliary system is over the low passes of the Remote feed switches, whereby with their own amplifiers a reasonably correct level (equal level) low-frequency connection is created in both transmission directions and being in normal operation on the respective non-monitoring terminal of the monitoring section and, in the event of a fault, in the last one still intact intermediate generator a cross connection of defined attenuation between outward and backward Reverse direction of the subsystem is formed (loop system, see Fig. 2; device technology in the repeaters, see Fig. 3). The amplifiers can also be used as regenerative amplifiers for the carrier frequency Pulse telegram must be executed.

The following explanations are given for the design of all facilities. The possible one The frequency range for the test channel is approx. 5 kHz to approx. 100 kHz. A certain selection against external influencing voltages is required. Under certain circumstances, this selection is already partly made by the for Remote feed applied to existing points anyway. With regard to disturbances (also with regard to Crosstalk) is the high-frequency range, with regard to attenuation the low-frequency range is more favorable.

A test channel without amplification is also at 5 kHz, taking into account the effects of the remote feeders not feasible for the usual, approximately 300 km long underground pipe sections. Considering the additional Difficulties with high level differences are also regenerative or non-regenerative Amplifier appropriate. In this case, these amplifiers are only used in "one" direction at each intermediate point (see. Fig. 3) provided and set alternately so that one amplifier always the attenuation of two fields cancels.

For the attenuating cross connection (through-connection) between the forward and backward directions, there is attenuation of the order of 15 dB is appropriate. Such a level difference between the sending and receiving directions is readily apparent in the monitoring station compensable. The attenuating cross-connection is in normal operation in the non-monitoring terminal Permanently or switchably switched on (connection ζ. Β. possible through switching sockets in the receptacle for the monitoring device in the remote terminal, or through switches in this monitoring device). The attenuation is necessary to prevent self-excitation of the line in the event of an error. One the same Damping through-connection must be effective in the remotely powered repeaters when the Loop connection responds.

The query is made by continuously calling all individually addressed intermediate regenerators during normal operation from the respective selected monitoring point by means of a carrier-frequency pulse telegram via the subsystem. As in the range of approximately 10 ^sixth . . ΙΟ " ⁹ is located (Fig. 4).

For the permanent, periodic calling of all repeaters will - even with partial assembly

ίο a route - always the same carrier-frequency transmitted pulse telegram according to Fig. 4 is used, with which the existing repeaters are requested to send a message.
Each repeater is equipped with an order

IS number, which is assigned to one of the 208 time slots after the start impulse. The interrogation pulse at the beginning of the assigned time slot serves both as a call to the relevant repeater and as a time reference mark for the "good" or "bad" signal emitted by the repeater after the call (see FIG. 5). the repetition frequency of the query telegram provides a measure of the error rate.
The feedback circuit can expediently be designed in such a way that the query or feedback frequency for synchronizing the feedback oscillator (VCO) is continuously transmitted at a low level (approx . The feedback pulses are derived precisely from the monitoring frequency (16 periods per pulse). An example of the design of the devices is explained below.
Fig. 3 shows that the incoming pulse telegram

(Fig. 4) is divided into three directions behind the monitoring amplifier 15. Once it arrives directly via the coupling 20 back to the line behind the repeater 9. Second, in the phase comparator 16 and in the following oscillator 17 the pulse carrier frequency is evaluated and in phase processed. Thirdly, the carrier frequency of the pulses is suppressed in the rectifier circuit 21, see above that the demodulated pulses (FIG. 4) can correctly advance the counter 22. With the decoder 23 the counter 22 is addressed so that it only emits an output pulse when the incoming pulse number the address set in the decoder has been reached. This output pulse of the counter 22 causes a further counter 18 is released and, from the

so controlled pulse carrier frequency, emits a 16 period wide pulse. This impulse is, as in Fig. 5, added to the pulse telegram in the coupling 20 via the AND gate 19, offset in time to the associated transmission pulse. The OR gate 24 determines the exact timing of the response pulse. At the output of the regenerator 9, an associated response pulse occurs in addition to the transmission pulses (FIG. 4). In subsequent remotely fed intermediate generators 2, all previously added response pulses must of course be suppressed at the input of the counting circuit 22 so that this counter 22 can initiate the connection of its own response pulse at the right moment.
If the amplifier 15 is designed as a pulse-regenerated amplifier, it must be ensured in a suitable manner that the carrier continuously transmitted for synchronization at a low level and the pulse to be regenerated are treated separately.

In the formation of the subsystem to safeguard against fullness, the LF amplifier is for the continuous Signals designed so that a passive through connection with an attenuation of about 20 dB results in case of amplifier failure. At this level, there should be none in the following repeaters Impulse response can be delivered. An evaluation in the monitoring terminal is then still possible.

In the monitoring terminal, information about the status of all possible items is collected with each query Repeater on, whereby by the training or switching of the monitoring devices certain information can be selected or suppressed as desired (e.g. a certain Repeater can be switched to a register device).

In the case of determining the location of the error in the event of a »cable break« or main system error, the calls and the feedback is used to determine the last intact intermediate regenerator, provided that is that by means of a loop closure circuit, the intact intermediate regenerators with remote feed current are supplied.

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Claims (6)

Patent claims: 1. Procedure for monitoring and locating faults in PCM transmission systems, which terminals and repeaters included, without interrupting the normal flow of messages with the aid a low-frequency superimposed test signal, characterized in that in each Repeater that monitors the outward and return lines, that the individual repeaters are transmitted by a monitoring terminal Carrier-frequency short-term impulse telegram, the one represented by the envelope of the carrier Pulse sequence exists, can be queried cyclically, whereby by changing the frequency of the Transmission of the pulse telegrams, the respective bit error rates achieved in the relevant intermediate regenerator .be recognizable that the respective repeater after the Calling up a carrier-frequency pulse telegram response is added, which provides a statement about the exceedance or not exceeding a certain error limit in the relevant repeater Kefert, that not exceeding this error limit a first response pulse at the earliest immediately after the interrogation pulse and a second response pulse if this error limit is exceeded triggers with a delay of at least the pulse duration of the first response pulse, that only in the other state, the loop for the Test channel is formed, that in the case of fault location. the nearest fault location is marked by the position of the response pulse in the pulse telegram,
that in the event of a total failure, the loop for the test channel in the last repeater before the fault location is closed, ίο that the position of the first missing response pulse in the pulse telegram is the error location of the total failure marked and that the evaluation of all or specifically selected response pulses in the monitoring terminal he follows. 2. The method according to claim 1, characterized in that the frequency of the low frequency Test signal is placed in the range between S kHz and 100 kHz. 3. The method according to claim 1, characterized in that the carrier-frequency pulse telegram is amplified by means of amplifiers in the conduction path or regenerated by means of regenerating amplifiers will. 4. The method according to claim 1, characterized in that that the pulse telegram is made up of a binary number of pulses, that a longer initial pulse as a synchronization pulse, the feedback circuits of all repeaters sets in the initial state. that the individual interrogation pulses follow after the synchronization pulse and that the distance between two interrogation pulses is chosen so large that there between at least two response pulses can be accommodated. 5. The method according to claim 1, characterized in that that consequential errors in the display device are suppressed by a logic circuit in the monitoring terminal will. 6. The method according to claim 1, characterized in that that in the event of a total failure the loop closing circuit for the feedback signals only have a cross connection between the two transmission directions creates the loop termination resistance without additional HF switching.