JP2590896B2 - PCM signal relay circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for a PCM signal relay circuit that relays and transmits a PCM multiplex signal generated by synchronously multiplexing a plurality of low-order PCM signals. In particular, it is used for a method of inserting an alarm propagation prevention signal (hereinafter, referred to as an AIS signal) of a PCM signal relay circuit.

〔Overview〕

The present invention provides a PCM signal relay circuit that relays and transmits a PCM multiplexed signal, detects the presence or absence of a low-order PCM signal to be inserted from the outside, and when the inserted signal is cut off, detects an AI based on the signal cutoff detection signal.
By inserting the S signal instead, when the low-order PCM signal to be inserted from the outside is cut off, the low-order PCM signal is prevented from being dropped out of the high-order PCM signal that is multiplexed and transmitted, and is transmitted to the next repeater. Is maintained in a normal state.

[Conventional technology]

FIG. 2 is a block diagram of a conventional PCM signal relay circuit.

Conventionally, a PCM signal relay circuit having an AIS insertion means separates a synchronously multiplexed high-order PCM signal a into a plurality of low-order PCM signals b to e as shown in FIG.
It has means for monitoring whether the CM signals b to e are in a synchronous state, selecting the synchronous signal in the synchronous state, and switching the low-order PCM signal in that state to the AIS signal in the asynchronous state. In order to provide a small-scale main signal processing means even for a repeater having a signal relay circuit, a selection circuit 3 for sending out a low-order PCM signal j to the outside and a switching circuit 4 for inserting a low-order PCM signal m from outside are provided. Was.

[Problems to be solved by the invention]

However, such a conventional PCM signal relay circuit, when inserting a low-order PCM signal from the outside, one of the low-order PCM signals that are multiplexed when the signal is cut off will be missing, multiplexed The mark ratio of the PCM signal fluctuates, and particularly in the case of optical transmission, the signal transmission state between the electrical-optical converter and the optical-electrical converter becomes unstable. In addition, since the frame constituted therein is also lost due to the loss of the low-order PCM signal, an unnecessary alarm is generated in the next repeater.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks, and the high-order signal multiplexed and transmitted when the low-order signal inserted from the outside is cut off.
It is an object of the present invention to provide a PCM signal relay circuit that can prevent a low-order PCM signal in a PCM signal from being lost and keep a transmission signal to a next repeater in a normal state.

[Means for solving the problem]

The present invention provides a demultiplexing circuit that demultiplexes a multiplexed high-order PCM signal and separates the multiplexed high-order PCM signal into a plurality of low-order PCM signals, inputs the plurality of low-order PCM signals, and selects one of the plurality of low-order PCM signals. A selection circuit for transmitting one low-order PCM signal to the outside and outputting the same, and a switching circuit for outputting one low-order PCM signal input from the outside in place of the low-order PCM signal sent to the outside, Multiple low-order PCMs output by the switching circuit
A multiplexing circuit for multiplexing a signal and outputting it as a high-order PCM signal, a synchronization monitoring circuit for monitoring the separated low-order PCM signal, and an alarm-spreading-prevention signal generating circuit that generates an alarm-spreading-preventive signal; The presence or absence of the externally inserted low-order PCM signal in the PCM signal relay circuit including means for outputting the alarm propagation prevention signal in place of the low-order PCM signal when the synchronization monitoring circuit detects that the low-order PCM signal is in an asynchronous state The switching circuit includes means for outputting the alarm propagation prevention signal in place of the low-order PCM signal inserted from the outside based on the signal disconnection detection signal of the detection circuit. I do.

[Action]

A detection circuit detects the presence or absence of a low-order PCM signal inserted from outside. When the low-order PCM signal inserted from the outside is cut off by the switching circuit, an alarm propagation prevention signal is inserted and output instead of the low-order PCM signal inserted from the outside based on the signal cutoff detection signal of the detection circuit. With the above operation, when the low-order PCM signal inserted from the outside is cut off, the low-order PCM signal is prevented from being dropped out of the high-order PCM signals multiplexed and transmitted, and the transmission signal to the next repeater is Can be kept in condition.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a PCM signal relay circuit according to one embodiment of the present invention. In FIG. 1, a PCM signal relay circuit includes a separating circuit 1 that receives a high-order PCM signal a in which four channels are multiplexed from outside, separates the multiplexed signal, and outputs low-order PCM signals b to e. A low-order PCM signal from b to e to determine the synchronization state, and when there is a low-order PCM signal that is not in the synchronization state, output a AIS switching instruction signal for instructing insertion of an AIS signal instead of the signal. 2 and
The low-order PCM signals b to e are input from the separation circuit 1 and
One of the signals b to e is selected and sent to the outside as a low-order PCM signal j, and the low-order PCM signals f to h are output in a state where one of the low-order PCM signals is missing. A selection circuit 3 for outputting an insertion instruction signal 1; an AIS generation circuit 5 for generating AIS signals o to r;
The low-order PCM signal m is input from the selection circuits f to h and the outside, and out of synchronization among the low-order PCM signals f to h and the AIS signal o according to the AIS switching instruction signal k from the synchronization monitoring circuit 2.
To r, and outputs the selected low-order signal.
A switching circuit 4 for inserting the low-order PCM signal m in place of the PCM signal j and outputting the low-order PCM signals s to v;
A multiplexing circuit 6 for receiving the PCM signals s to v and outputting a high-order PCM signal w out of the figure;

Here, a feature of the present invention is that the switching circuit 4 includes a detection circuit 7 that detects the presence or absence of a low-order PCM signal m input from the outside and supplies a signal disconnection detection signal n to the switching circuit 4. and means for inserting and outputting any one of the AIS signals o to r instead of the low-order PCM signal m according to n.

The operation of the PCM signal relay circuit having such a configuration will be described. In FIG. 1, the high order PCM signal a is separated into low order PCM signals be. Any of the low-order PCM signals b to e is sent out to the outside by the selection circuit 3 as the low-order PCM signal j. The remaining low-level signals f to h (i.e.,
The asynchronous circuit is switched by the switching circuit 4 to one of the AIS signals o to r in accordance with the AIS switching instruction signal k of the synchronous monitoring circuit 2. Also, the low-order PCM signal j sent out by the switching circuit 4 to the outside according to the insertion instruction signal 1 of the selection circuit 2
Is inserted instead of the low-order PCM signal m. In addition, lower PCM
The low-order PCM signal m to be inserted from the outside instead of the signal j is output to one of the AIS signals o to r by the signal disconnection detection signal n of the detection circuit 7 for detecting the presence or absence of the signal when the low-order PCM signal m is disconnected. Can be switched. Thus, it is possible to prevent a signal from being lost in a part of the signal sequence of the low-order PCM signals s to v.

[Effects of the Invention] As described above, the present invention detects the presence or absence of a low-order PCM signal to be inserted from the outside, so that when the insertion signal is cut off, the high-order PCM signal multiplexed and transmitted is detected. Thus, there is an excellent effect that one low-order PCM signal can be prevented from being lost, and the transmission signal to the subsequent relay disconnection can be kept normal.

[Brief description of the drawings]

FIG. 1 is a block diagram of a PCM signal relay circuit according to an embodiment of the present invention. FIG. 2 is a block diagram of a conventional PCM signal relay circuit. DESCRIPTION OF SYMBOLS 1 ... Separation circuit, 2 ... Synchronization monitoring circuit, 3 ... Selection circuit, 4 ... Switching circuit, 5 ... AIS generation circuit, 6 ... Multiplexing circuit, 7 ... Detection circuit, a, w ... High order PCM signal, b ~
i, j, m, s to v: low-order PCM signal, k: AIS switching instruction signal, l: insertion instruction signal, n: detection signal, or
…… AIS signal.

Claims (1)

(57) [Claims] 1. A demultiplexing circuit for demultiplexing a multiplexed high-order PCM signal to separate the plurality of low-order PCM signals into a plurality of low-order PCM signals. A selection circuit for selecting and sending out to the outside a low-order PCM signal, and a switching circuit for outputting one low-order PCM signal input from the outside in place of the low-order PCM signal sent to the outside; A multiplexing circuit that multiplexes a plurality of low-order PCM signals output from the switching circuit and outputs the multiplexed low-order PCM signals as a high-order PCM signal; a synchronization monitoring circuit that monitors the separated low-order PCM signal; and an alarm spillover that generates an alarm spillover prevention signal. Wherein the switching circuit comprises means for outputting the alarm propagation prevention signal instead of the low-order PCM signal when the synchronization monitoring circuit detects that the synchronization monitoring circuit is in an asynchronous state. , Up A detection circuit for detecting the presence or absence of a low-order PCM signal to be inserted from the outside; the switching circuit detects the alarm propagation prevention signal instead of the low-order PCM signal to be inserted from the outside based on a signal cutoff detection signal of the detection circuit. A PCM signal relay circuit comprising output means.