JPS639697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In a PCM multiplexer using a staff synchronization method, the present invention eliminates speed fluctuations of low-order group signals input to the PCM multiplexer and clock system failures within the PCM multiplexer. Monitor by detecting whether the rate is within a predetermined range
This article relates to a monitoring method in a PCM multiplexing device.

The configuration of the PCM multiplex conversion system according to the present invention is explained as follows.
As shown in the figure. In this figure, 1 is a PCM multiplexing device;
2 is a PCM demultiplexing device, 3 is a multiplexing section, 4 is a demultiplexing section, 5 is a channel section on the multiplexing side, 6 is a channel section on the demultiplexing side, 7 is an input signal from a lower order group, 8
9 is a transmission line, and 10 is a monitoring line.

The input signal 7 from the lower order group is transmitted to each channel section 5.
The signals are synchronized with the clock of the PCM multiplexer 1 by staff synchronization, time-division multiplexed by the multiplexer 3, and sent to the transmission line 9. In the PCM demultiplexer 2, the multiplexed signal from the transmission line 9 is demultiplexed into each channel section 6 by the demultiplexer section 4, and in each channel section 6, the clock rate of the input signal 7 from the lower order group is regenerated by the PLL circuit. and output signal 8 to the lower order group.

Conventionally, in the above-mentioned PCM multiple conversion system,
In the PCM multiplexing device 1, the speed fluctuation of the input signal 7 from the lower order group was not monitored. Also
For the clock system in the PCM multiplexer 1,
Monitoring was only carried out to the extent of detecting clock breaks. By the way, when the above-mentioned fault occurs, the demultiplexing device 2 detects that there is a fault in the signal sent from the multiplexing device 1, and the monitoring line 10
Therefore, an alarm was issued to the multiplexer 1 side.
However, in this case, even if it is known that there is a fault in the multiplexed signal input to the PCM demultiplexer 2,
Since it is not clear whether the cause lies in the PCM multiplexer 1 or the signal 7 from the lower order group, the search in the multiplexer was complicated. In addition to the above-mentioned reasons, CCITT also stipulates the allowable range of the speed fluctuation of the input signal 7 from the low-order group, and the fluctuation of the input signal 7 from the low-order group and the Monitoring of the clock system is necessary.

The present invention eliminates the above-mentioned runner-up point and makes it clear whether the fault is in the PCM multiplexing device 1 or in the input signal 7 from the lower order group when a fault occurs, thereby reducing the search time for the fault location. In order to achieve this purpose, a PCM multiplexing device 1 using a stuff synchronization method is provided with a stuff ratio monitoring circuit in each channel section 5 to reduce the staff ratio of stuffed low-order group signals. This system is characterized in that a staff rate monitoring circuit monitors whether or not the staff rate is within a predetermined range.

The staff synchronization method according to the present invention will be explained below. In the PCM multiplexer 1, staff operations are performed in each channel section 5. FIG. 2 is a diagram showing the configuration of the channel section 5. As shown in FIG. In this figure, 11 is a buffer memory, 12 is a write clock extraction circuit, 13 is a phase comparator, and 14 is a buffer memory.
1 is a staff control circuit, 15 is a frequency divider, 16 is a clock source, 17 is a write clock, 18 is a read clock, 19 is a staff request signal, and 20 is a synchronization signal. Note that the same numbers as in FIG. 1 indicate the same parts.

In the staff synchronization method, the input signal 7 from the asynchronous low-order group is once written into the buffer memory 11 using the write clock 17 extracted by the write clock extraction circuit 12, and synchronized by reading it out using the read clock 18 whose speed is slightly faster than the write clock 17. It takes . However, since the read clock 18 is set at a slightly faster speed than the write clock as described above, the phase of the write clock 17 gradually lags, resulting in a period in which there is no signal to be read. Therefore, the phase comparator 13 compares the phases of the write clock 17 and the read clock 18, and when the difference approaches 1 bit, it sends a staff request signal 19 to the staff control circuit 14.
4 stops the read clock 18 by one bit. When the read clock 18 is stopped by one bit in this way, one stuff pulse is inserted into the synchronization signal.

The above operation will be further explained using the time chart shown in FIG. FIG. 3 shows how the input signal 7 from the lower order group is synchronized in the channel section 5 and a stuff pulse is inserted. In this figure, 21 is a clock pulse that is stopped;
22 is a stuff pulse. a is a low-order group signal train, b is a readout clock pulse train, and c is a synchronization signal train. The read clock pulse 21 is stopped by the stuff control circuit 14 when the phase difference between the write clock 17 and the read clock 18 becomes close to 1 bit, and as a result, the stuff pulse 22 is inserted into the synchronization signal example. .

The frequency of insertion of the above-mentioned stuff pulses 22 is called the stuff rate, and if the speed of the input signal 7 from the lower order group is constant, the stuff rate also shows a certain constant value. However, if the actually input signal speed becomes slower than the specified signal speed, the number of times the stuff pulse 22 is inserted in a certain period of time increases, and the stuff rate also increases. On the other hand, as the input signal speed increases, the stuff factor also decreases. The present invention utilizes the fact that, as described above, when the speed of the input signal 7 from the lower order group changes, the stuff rate also changes.

An embodiment of a monitoring method in a PCM multiplexing device according to the present invention will be described in detail below using the drawings.

FIG. 4 is a diagram showing an embodiment of a monitoring method in a PCM multiplexing apparatus according to the present invention. In the figure, 23 is a staff rate monitoring circuit, 24 is a determination circuit, and 25 is an alarm circuit. Note that the same numbers as in FIGS. 1 and 2 indicate the same parts. The staff rate monitoring circuit 23 provided in each channel section 5 is as follows:
The speed fluctuation of the input signal 7 from the lower order group is monitored for fluctuations out of the permissible range for the PCM multiplexing device 1 .

In the monitoring method for the PCM multiplexing device according to the present invention, the above-mentioned staff rate is monitored by monitoring the staff control circuit 14 and counting staff command pulses within a certain period of time.

FIG. 5 is an example of a staff rate monitoring circuit used in the present invention.

In this figure, 27 is a decimal counter, 28 is a multi-input OR gate, 29 is a D flip-flop, and 3
0 is a timer, 31 is a delay circuit, 32 is a staff command pulse, 33 is a terminal whose output becomes "H" level when the staff rate is within the allowable range, and 34 is a terminal whose output is "H" level when the staff rate is 100%. The terminal 35 which becomes H" level is the output terminal of the D flip-flop.

The staff rate monitoring circuit shown in this figure is a timer 30.
The number of staff command pulses within the time set by 10
This is counted by a digit counter 27. terminal 33
calculates and sets the number of staff command pulses within a certain period of time from the variation range of staff rate allowed for the PCM multiplexer 1. Further, the terminal 34 is determined based on the number of command pulses when the stuff rate is 100%. Note that for the following explanation, the lower limit of the allowable number of staff command pulses is Q _L and the upper limit is Q _H.

If the fluctuation in the speed of the input signal from the low-order group is within the allowable range, the number of staff command pulses is between Q _L and Q _H , so one of the input terminals of the multi-input OR gate 28 is “ Since the output goes to "H" level, the output also goes to "H" level, and the D flip-flop 2
9 and the terminal 34 becomes "H" level. Furthermore, if the speed fluctuation of the input signal from the lower order group is outside the allowable range, the number of staff command pulses will be less than Q _L-1 or more than Q _H+1 , so the multi-input OR gate 28
Since all the input terminals of the D flip-flop are at the "L" level, the output terminal 35 of the D flip-flop is also at the "L" level. Therefore, the output terminal 34 of the D flip-flop will be at the "H" level if the speed fluctuation range of the input signal from the lower order group is within the permissible range, and will be at the "L" level if it is outside the permissible range. . Also, if it is a non-implemented channel, the staff rate will be 100%.
The output terminal 34 of the decimal counter 27 becomes "H" level. Note that the delay circuit 31 in FIG.
Decimal counter 2 after storing in flip-flop
This is for resetting 7.

The output terminal 35 of the D flip-flop and the output terminal 34 of the decimal counter of the above-mentioned stuff rate monitoring circuit.
is connected to the determination circuit 24 shown in FIG. If these stuff ratios are outside the allowable range, the determination circuit 24 determines that this is a speed fluctuation of the signal 7 from the lower order group input to that channel. Further, if the staff rate is outside the allowable range in all channels or if the staff rate does not reach 100% in a non-implemented channel, it is determined that there is a failure in the clock system, and the alarm circuit 25 issues an alarm.

As explained above, the present invention enables the PCM multiplexing device 1 to monitor the stuff rate that changes with the speed fluctuation of the input signal 7 from the low-order group, and the PCM demultiplexing device 2 to the monitoring line 10. When a fault alarm is received on the multiplexer 1 side, whether multiplexing is not performed correctly in the multiplexer 3 due to a failure in the clock system within the PCM multiplexer, or whether the low voltage input to the PCM multiplexer 1 Since it is known which signal 7 from the next group has a fault, the time required to search for the fault can be reduced.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the PCM multiplex conversion system, Figure 2 is
A diagram showing the configuration of a PCM multiplexing device, FIG. 3 is an explanatory diagram of staff synchronization, and FIG. 4 is a diagram according to the present invention.
An example of a monitoring method in a PCM multiplexing device,
FIG. 5 is a diagram showing an embodiment of the staff rate monitoring circuit according to the present invention. 3... Multiplexing unit, 7... Input signal from low-order group, 9... Transmission path, 11... Buffer memory, 1
2... Write clock extraction circuit, 13... Phase comparator, 14... Staff control circuit, 15... Frequency divider, 16... Clock source, 17... Write clock, 18... Read clock, 19... Staff request signal, 20...Synchronization signal, 27...
Decimal counter, 28...Multi-input OR gate, 2
9...D flip-flop, 30...timer,
31...Delay circuit, 32...Staff command pulse, 33...Output terminal, 34...Output terminal, 35
...Output terminal.

Claims (1)

[Claims] 1. In a PCM multiplexing device using the stuff synchronization method, a stuff rate monitoring circuit is provided in each channel section that performs stuffing on signals from the low order group to be multiplexed, and 1. A monitoring method for a PCM multiplexing device, characterized in that the staff rate monitoring circuit monitors whether or not the staff rate is within a predetermined range.