JPH0787446B2 - Digital signal transmission system - Google Patents

Digital signal transmission system

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Publication number
JPH0787446B2
JPH0787446B2 JP920489A JP920489A JPH0787446B2 JP H0787446 B2 JPH0787446 B2 JP H0787446B2 JP 920489 A JP920489 A JP 920489A JP 920489 A JP920489 A JP 920489A JP H0787446 B2 JPH0787446 B2 JP H0787446B2
Authority
JP
Japan
Prior art keywords
line
working
protection
circuit
quality
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP920489A
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Japanese (ja)
Other versions
JPH02190042A (en
Inventor
知之 倉橋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP920489A priority Critical patent/JPH0787446B2/en
Publication of JPH02190042A publication Critical patent/JPH02190042A/en
Publication of JPH0787446B2 publication Critical patent/JPH0787446B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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  • Detection And Prevention Of Errors In Transmission (AREA)

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は複数の現用回線と共に予備回線を有し、現用回
線の品質が劣化したときに予備回線に切り替える方式の
デジタル信号伝送方式に関する。The present invention relates to a digital signal transmission system having a plurality of working lines and a protection line and switching to the protection line when the quality of the working line deteriorates.

〔従来の技術〕[Conventional technology]

従来、この種のデジタル信号伝送方式では、現用回線の
品質を検出し、この検出値を予め設定された値と比較し
た上で回線を切り替えるようにしている。この回線品質
検出方法としては、パリティーパルス、或いはシンドロ
ームパルスを用いて誤り率を求める方法が用いられてい
る。即ち、ある特定の現用回線の受端局で検出した誤り
率が、予め定められた誤り率より悪いときに該回線から
回線障害アラームを発動する。そして、このとき予備回
線が、他の現用回線に用いられておらず、しかも誤り率
が予め定められた値よりも低い場合に、回線障害アラー
ムを発動した現用回線を予備回線へ切替えている。Conventionally, in this kind of digital signal transmission system, the quality of the working line is detected, and the line is switched after comparing the detected value with a preset value. As the line quality detecting method, a method of obtaining an error rate using a parity pulse or a syndrome pulse is used. That is, when the error rate detected by the receiving end station of a certain working line is worse than a predetermined error rate, a line fault alarm is issued from the line. At this time, if the protection line is not used for another working line and the error rate is lower than a predetermined value, the working line that has issued the line failure alarm is switched to the protection line.

この一例を第２図に示す。ここでは、３本の現用回線28
1〜283及び１本の予備回線29を持つ装置を用いてデジタ
ル信号D1〜D3を伝送する場合の従来の回線切り替え方式
について説明する。An example of this is shown in FIG. Here, three working lines 28
It described conventional line switching method when transmitting digital signals D 1 to D 3 using an apparatus having 1 to 28 3 and one protection line 29.

この伝送方式は、誤り率に基づいて受端局Ｒで回線品質
を常に監視し、この誤り率が予め定められた値よりも悪
い場合、換言すれば回線品質が規定の値よりも劣化した
場合に、現用から予備へ回線を切り替える。In this transmission method, the receiving end station R constantly monitors the line quality based on the error rate, and when the error rate is worse than a predetermined value, in other words, when the line quality deteriorates below a specified value. Then, the line is switched from the working to the protection.

いま仮に、現用送信回路221と現用受信回路241からなる
現用回線281でフェージング等が起こり回線品質が劣化
した場合を考える。受端局Ｒでは、まず現用受信回路24
1で誤り率を検出した後、その誤り率の値を予め定めら
れた誤り率の値と比較し、劣化が確認されれば回線障害
アラームを発動する。発生した回線障害アラームは回線
切替制御回路27に送られる。Consider a case where fading or the like occurs in the working line 28 1 including the working transmission circuit 22 1 and the working reception circuit 24 1 and the line quality is deteriorated. In the receiving terminal R, first, the working receiving circuit 24
After detecting the error rate in 1 , the error rate value is compared with a predetermined error rate value, and if deterioration is confirmed, a line failure alarm is activated. The generated line failure alarm is sent to the line switching control circuit 27.

この時、現用送信回路222及び現用受信回路242からなる
現用回路282と、現用送信回路233及び現用受信回路243
からなる現用回線283と、予備送信回路23及び予備受信
回路25からなる予備回線29とにおいても、夫々同様にし
て誤り率の値を予め定められた誤り率の値と比較し、劣
化していないことを確認したときには回線障害アラーム
を出さない。At this time, the working circuit 28 2 comprising an active transmitter circuit 22 2 and the working receiving circuit 24 2, current transmission circuit 23 3 and the working receiving circuit 24 3
A working line 28 3 consisting, in the protection line 29. consisting of pre-transmission circuit 23 and the standby receiving circuit 25, and respectively similar compared to the value of the predetermined error rate value of the error rate, not deteriorate If you confirm that there is no line fault alarm.

回線切替制御回路27では予備受信回路25、現用受信回路
242及び現用受信回路243より回線障害アラームを受信し
ないことで、現用回線282及び現用回線283が予備回線29
を占有していないことを確認すると共に、予備回線29で
回線障害が起きていないことを確認する。このとき予備
回線の回線障害アラーム発動点は３本の現用回線のそれ
と等しい。The line switching control circuit 27 includes a standby receiving circuit 25 and a working receiving circuit.
By not receiving the line failure alarm from the 24 2 and the working reception circuit 24 3 , the working line 28 2 and the working line 28 3 are protected by the protection line 29.
It is confirmed that the backup line 29 is not occupied and that no line failure has occurred in the backup line 29. At this time, the line fault alarm activation point of the protection line is equal to that of the three working lines.

そして、予備回線29に回線障害アラームがでていなけれ
ば、回線切替制御回路27は送端回線切替回路21へ制御信
号を送り送端回線切替回路21を切り替え、現用回線281
により伝送されていたデジタル信号D1を予備回線29へも
伝送する。また、回線切替制御回路27は受端回線切替回
路26へ制御信号を送り、受端回線切替回路26を切り替え
て現用受信回路281から出力されるデジタル信号に代わ
って予備受信回路25から出力されるデジタル信号をデジ
タル信号D1として受端回線切替回路26より出力させる。If the line failure alarm does not occur on the protection line 29, the line switching control circuit 27 sends a control signal to the sending end line switching circuit 21 to switch the sending end line switching circuit 21, and the working line 28 1
The digital signal D 1 transmitted by the above is also transmitted to the protection line 29. Further, the line switching control circuit 27 sends a control signal to the receiving end line switching circuit 26 to switch the receiving end line switching circuit 26 and output from the standby receiving circuit 25 in place of the digital signal output from the working receiving circuit 28 1. The digital signal to be output is output from the receiving end line switching circuit 26 as the digital signal D 1 .

以上により現用回線281によって伝送されていたデジタ
ル信号D1の予備回線29への切り替えが終了する。As described above, the switching of the digital signal D 1 transmitted by the working line 28 1 to the protection line 29 is completed.

〔発明が解決しようとする課題〕[Problems to be Solved by the Invention]

上述した方式では、複数の現用回線に対して１本の予備
回線しか備えておらず、しかも各現用回線に対して予備
回線の回線障害アラームを一通りにしか選べない。この
ため、１つの現用回線が予備回線に切り替わった状態
で、他の現用回線に回線品質の劣化が生じた場合には、
予備回線がすでに占有されているため、他の現用回線を
予備回線に切り替えることができなくなる。また、現用
回線に回線品質による切り替え優先順位を持たせること
ができないため、他の回線の回線品質が一層劣化した場
合でも予備回線に切り替えることができず、伝送方式全
体としての品質が劣化されるという問題がある。In the above-mentioned method, only one protection line is provided for a plurality of working lines, and moreover, only one line failure alarm of the protection line can be selected for each working line. For this reason, if one working line is switched to the protection line and the other working line deteriorates in line quality,
Since the protection line is already occupied, another working line cannot be switched to the protection line. Further, since the working line cannot be given a switching priority depending on the line quality, even if the line quality of other lines is further deteriorated, it is not possible to switch to the protection line and the quality of the entire transmission system is deteriorated. There is a problem.

本発明は上述した問題を解消して高い回線品質を確保す
ることを可能にしたデジタル信号伝送方式を提供するこ
とを目的とする。It is an object of the present invention to provide a digital signal transmission system which can solve the above-mentioned problems and ensure high line quality.

〔課題を解決するための手段〕[Means for Solving the Problems]

本発明のデジタル信号伝送方式は、送端局と受端局とを
Ｎ本の現用回線とＭ本の予備回線で接続してなり、現用
回線を予備回線に切り替える送端回線切替回路と、現用
回線及び予備回線に接続され、送出するデジタル信号を
変調しかつ受端局において回線品質を検出するための情
報を付加する送信回路と、現用回線及び予備回線に接続
され、送出されてきた信号を復調しかつ回線品質を検出
する受信回路と、これら受信回路からの信号を選択して
Ｎ本の回線を出力する受端回線切替回路と、前記受信回
路に接続され、各回線の回線品質のしきい値を設定する
とともに、各回線の回線品質を検出してこれを設定され
た回線品質の前記しきい値と比べてその結果を出力する
回線品質検出回路と、これら回線品質検出回路から検出
された回線品質が前記予め設定された回線品質のしきい
値よりも低い品質を検出した際の出力に基づいて、前記
送端回線切替回路及び受端回線切替回路において現用回
線を予備回線に切り替え動作させ、Ｍ本以上の現用回線
を予備回線に切り替える場合にはこれらの現用回線に設
定されているしきい値の高い回線から優先的にＭ番目ま
での現用回線を予備回線に切り替え、かつ該切り替えた
予備回線の回線品質検出回路のしきい値を切り替えられ
た現用回線に設定されていた値に書き替える回線切替制
御回路とを備えている。According to the digital signal transmission system of the present invention, a sending end station and a receiving end station are connected by N working lines and M protection lines, and a transmission end line switching circuit for switching the working line to the protection line and a working line. A transmission circuit connected to the line and the protection line, which modulates the digital signal to be transmitted and adds information for detecting the line quality at the receiving end station, and a signal which is connected to the working line and the protection line and transmitted. A receiving circuit that demodulates and detects the line quality, a receiving end line switching circuit that selects signals from these receiving circuits and outputs N lines, and a line quality of each line connected to the receiving circuit. A line quality detection circuit that sets the threshold value, detects the line quality of each line, compares it with the threshold value of the set line quality, and outputs the result, and detects the line quality detection circuits. The line quality was Note: Based on the output when a quality lower than a preset line quality threshold is detected, the working line is switched to the protection line in the sending end line switching circuit and the receiving end line switching circuit, and M lines are operated. When switching the above working lines to the protection lines, the working lines up to Mth from the high threshold lines set in these working lines are preferentially switched to the protection lines, and And a line switching control circuit for rewriting the threshold value of the line quality detection circuit to the value set for the switched working line.

〔作用〕[Action]

上述した構成では、複数の現用回線の回線障害アラーム
の発動点となる回線品質しきい値を夫々任意に設定し、
かつ予備回線の回線品質しきい値を任意に変更させ、高
い品質の回線を優先させた切り替えが実現できる。In the above-mentioned configuration, the line quality thresholds that are the trigger points of the line failure alarms of the plurality of working lines are arbitrarily set,
In addition, the line quality threshold of the protection line can be arbitrarily changed, and switching can be realized by giving priority to a line of high quality.

〔実施例〕〔Example〕

次に、本発明を図面を参照して説明する。 Next, the present invention will be described with reference to the drawings.

第１図は本発明の一実施例のブロック図であり、ここで
は送端局Ｔと受端局ＲをＮ本の現用回線とＭ本の予備回
線で接続した例を示している。FIG. 1 is a block diagram of an embodiment of the present invention, and shows an example in which a transmitting terminal T and a receiving terminal R are connected by N working lines and M protection lines.

送端局Ｔにおいて、送端回線切替回路１はＮ本のデジタ
ル信号D1〜DNをＮ本の現用回線111〜11Nを通して送出す
るが、後述する受端局Ｒの回線切替制御回路７らの信号
により、その一部をＭ本の予備回線121〜12Mを通して送
出し得るようになっている。In Okutankyoku T, but the sending end line switching circuit 1 sends the digital signals D 1 to D N of the N through N number of working lines 11 1 to 11 N, the line switch control circuit of the reception terminal station R to be described later A part of them can be transmitted through the M protection lines 12 1 to 12 M by the signals of 7 and the like.

現用送信回路21〜2NはＮ本の現用回線111〜11Nに夫々接
続され、デジタル信号を変調する機能と回線品質を受端
局にて検出するための情報を付加する機能を有する。The working transmission circuits 2 1 to 2 N are respectively connected to the N working lines 11 1 to 11 N , and have a function of modulating a digital signal and a function of adding information for detecting line quality at the receiving end station. .

同様に、予備送信回路31〜3MはＭ本の予備回線121〜12M
に夫々接続され、デジタル信号を変調する機能と回線品
質を受端局にて検出するための情報を付加する機能を有
する。Similarly, the protection transmission circuits 3 1 to 3 M are M protection lines 12 1 to 12 M.
And has a function of modulating a digital signal and a function of adding information for detecting line quality at the receiving end station.

一方、受端局Ｒにおいて、現用受信回路41〜4Nは現用回
線111〜11Nに夫々接続され、これら現用回線を通して送
られてきた信号を元のデジタル信号に復調する機能と回
線品質を検出する機能を有する。On the other hand, in the receiving end station R, the working receiving circuits 4 1 to 4 N are connected to the working lines 11 1 to 11 N , respectively, and the function and line quality for demodulating the signals sent through these working lines to the original digital signals. Has the function of detecting.

同様に、予備受信回路51〜5Mは予備回線121〜12Mに夫々
接続され、これら予備回線を通して送られてくる信号を
元のデジタル信号に復調する機能と回線品質を検出する
機能を有する。Similarly, the backup receiver circuits 5 1 to 5 M are connected to the backup lines 12 1 to 12 M , respectively, and have the function of demodulating the signals sent through these backup lines to the original digital signals and the function of detecting the line quality. Have.

これらの現用受信回路41〜4N,及び予備受信回路51〜5M
は夫々受端回線切替回路６に接続される。この受端回線
切替回路６は、後述する回線切替制御回路７からの出力
により、送端局Ｔの送端回線切替回路１と共に現用回線
の一部を予備回線に切替え、デジタル信号D1〜DNを出力
する。These working receiver circuits 4 1 to 4 N , and spare receiver circuits 5 1 to 5 M
Are connected to the receiving end line switching circuit 6, respectively. The receiving end line switching circuit 6 switches a part of the working line to the protection line together with the sending end line switching circuit 1 of the sending end station T by the output from a line switching control circuit 7 described later, and digital signals D 1 to D 1 Output N.

そして、前記現用受信回路41〜4N及び予備受信回路51〜
5Mには夫々現用，予備の各回線品質検出回路81〜8N,91
〜9Mを接続している。これらの回線品質検出回路81〜
8N,91〜9Mは、現用回線111〜11N及び回線121〜12Mの夫
々の回線品質を検出する機能と、回線切替制御回路７に
より設定された回線品質のしきい値を比べその結果を回
線切替制御回路７に出力する機能を有している。Then, the working receiving circuits 4 1 to 4 N and the standby receiving circuit 5 1 to
Each of 5 M has a working and spare line quality detection circuit 8 1 to 8 N , 9 1
~ 9 M is connected. These line quality detection circuits 8 1 ~
8 N , 9 1 to 9 M is a function of detecting the line quality of each of the working lines 11 1 to 11 N and the lines 12 1 to 12 M , and the line quality threshold set by the line switching control circuit 7. And has a function of outputting the result to the line switching control circuit 7.

この構成によれば、送端局Ｔの各現用送信回路21〜2Nか
らの送出信号は、現用回線111〜11Nを通して現用受信回
路41〜4Nで受信を行ない、この信号は受端回線切替回路
６を通して出力される。これと同時に、現用回線品質検
出回路81〜8Nでは各現用回線111〜11Nの品質を検出す
る。そして、各回線の品質を回線切替制御回路７で設定
された回線品質しきい値と比較し、このしきい値よりも
低い品質を検出したときには、該当する現用回線の回線
品質検出回路から回線障害アラームを出力する。する
と、回線切替制御回路７は、回線障害の情報を送端局Ｔ
の送端回線切替回路１と受端局Ｒの受端回線切替回路６
に夫々出力し、該当する現用回線をＭ本の予備回線の一
つに切替える。According to this configuration, the sending signal from the working transmission circuits 2 1 to 2 N in Okutankyoku T performs a reception on the working receiving circuit 4 1 to 4 N through working lines 11 1 to 11 N, the signal It is output through the receiving line switching circuit 6. At the same time, the working line quality detecting circuits 8 1 to 8 N detect the quality of each working line 11 1 to 11 N. Then, the quality of each line is compared with the line quality threshold set by the line switching control circuit 7, and when a quality lower than this threshold is detected, the line quality detection circuit of the corresponding working line detects a line failure. Output an alarm. Then, the line switching control circuit 7 sends the line failure information to the sending terminal station T.
Sending end line switching circuit 1 and receiving end line switching circuit 6 of receiving end station R
Respectively, and the corresponding working line is switched to one of the M protection lines.

この際、回線切替制御回路７では、予備回線側の回線品
質検出回路91〜9Mにおける回線品質のしきい値を、切り
替えようとする現用回線に要求されているしきい値に書
き替える。At this time, the line switching control circuit 7, the threshold value of the channel quality in the channel quality detecting circuit 9 1 to 9 M of protection line side, rewrites the threshold that is required to the working line to try to switch.

この切り替えは、現用回線の障害が、予備回線の本数で
あるＭ個に達するまで行われる。This switching is performed until the number of faults on the working line reaches M, which is the number of protection lines.

一方、Ｍ本以上の現用回線の回線品質検出回路から回線
障害アラームが出力された場合は、回線品質検出回路の
しきい値の高い現用回線からＭ番目までの現用回線を予
備回線に切り替える。このとき、予備回線側のＭ個の回
線品質検出回路の回線品質のしきい値を、切り替えよう
とする現用回線に要求されているしきい値にそれぞれ書
き替える。On the other hand, when a line failure alarm is output from the line quality detection circuits of M or more working lines, the working lines having a high threshold of the line quality detection circuit are switched to the Mth working lines to the protection lines. At this time, the line quality thresholds of the M line quality detection circuits on the protection line side are rewritten to the thresholds required for the working line to be switched.

したがって、この方式では、複数の現用回線を瞬時に予
備回線に切替えることが可能となり、しかも現用回線に
おける品質の高いものから優先的に予備回線に切替える
ことができ、伝送されるデジタル信号の品質を高いもの
に確保することが可能となる。Therefore, in this method, it is possible to instantaneously switch a plurality of working lines to a protection line, and it is possible to preferentially switch to a protection line from a working line having a high quality, so that the quality of a transmitted digital signal is improved. It is possible to secure a high price.

〔発明の効果〕〔The invention's effect〕

以上説明したように本発明は、複数の現用回線に対し
て、予備回線の回線品質しきい値を切り替えようとする
現用回線のしきい値にリアルタイムで設定できるため、
回線品質による切り替え優先順位を現用回線に持たせ、
常に高い回線品質での伝送が実現できるという効果があ
る。As described above, according to the present invention, for a plurality of working lines, the threshold value of the working line for which the line quality threshold of the protection line is about to be switched can be set in real time.
Give the working line a priority for switching depending on the line quality,
The effect is that transmission can always be achieved with high line quality.

【図面の簡単な説明】[Brief description of drawings]

第１図は本発明の一実施例のブロック図、第２図は現用
回線３本及び予備回線１本を持つ従来のデジタル信号伝
送方式のブロック図である。 １……送端回線切替回路、21〜2N……現用送信回路、31
〜3M……予備送信回路、41〜4N……現用受信回路、51〜
5M……予備受信回路、６……受端回線切替回路、７……
回線切替制御回路、81〜8N……現用回線品質検出回路、
91〜9M……予備回線品質検出回路、111〜11N……現用回
線、121〜12M……予備回線、D1〜DN……デジタル信号、
21……送端回線切替回路、221〜223……現用送信回路、
23……予備送信回路、241〜243……現用受信回路、25…
…予備受信回路、26……受端回線切替回路、27……回線
切替制御回路。FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional digital signal transmission system having three working lines and one protection line. 1 …… Sending line switching circuit, 2 1 to 2 N …… Current transmission circuit, 3 1
~3 M ...... spare transmission circuit, 4 1 ~4 N ...... working reception circuit 51 to
5 M …… Preliminary receiving circuit, 6 …… Receiving line switching circuit, 7 ……
Line switching control circuit, 8 1 to 8 N ... Working line quality detection circuit,
9 1 to 9 M ...... Protection line quality detection circuit, 11 1 to 11 N ...... Working line, 12 1 to 12 M ...... Protection line, D 1 to DN ...... Digital signal,
21 …… Sending line switching circuit, 22 1 to 22 3 …… Current transmission circuit,
23 …… Preliminary transmitting circuit, 24 1 to 24 3 …… Current receiving circuit, 25…
… Preliminary receiving circuit, 26 …… Reception line switching circuit, 27 …… Line switching control circuit.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】送端局と受端局とをＮ本の現用回線とＭ本
の予備回線で接続してなり、前記現用回線を前記予備回
線に切り替える送端回線切替回路と、前記現用回線及び
予備回線に接続され、送出するデジタル信号を変調しか
つ受端局において回線品質を検出するための情報を付加
する送信回路と、前記現用回線及び予備回線に接続さ
れ、送出されてきた信号を復調しかつ回線品質を検出す
る受信回路と、これら受信回路からの信号を選択してＮ
本の回線を出力する受端回線切替回路と、前記受信回路
に接続され、各回線の回線品質のしきい値を設定すると
ともに、各回線の回線品質を検出してこれを設定された
回線品質の前記しきい値と比べてその結果を出力する回
線品質検出回路と、これら回線品質検出回路から検出さ
れた回線品質が前記予め設定された回線品質のしきい値
よりも低い品質を検出した際の出力に基づいて、前記送
端回線切替回路及び受端回線切替回路において現用回線
を予備回線に切り替え動作させ、Ｍ本以上の現用回線を
予備回線に切り替える場合にはこれらの現用回線に設定
されているしきい値の高い回線から優先的にＭ番目まで
の現用回線を予備回線に切り替え、かつ該切り替えた予
備回線の回線品質検出回路のしきい値を切り替えられた
現用回線に設定されていた値に書き替える回線切替制御
回路とを備えることを特徴とするデジタル信号伝送方
式。1. A transmission line switching circuit for connecting a transmission line station and a reception line station by N working lines and M protection lines, and switching the working line to the protection line, and the working line. And a transmission circuit connected to the protection line, which modulates the digital signal to be transmitted and adds information for detecting the line quality at the receiving end station, and a signal which is connected to the working line and the protection line and transmitted. The receiving circuits that demodulate and detect the line quality, and the signals from these receiving circuits are selected to select N
It is connected to the receiving line switching circuit that outputs one line and the receiving circuit, sets the line quality threshold of each line, detects the line quality of each line, and sets this line quality. When a line quality detection circuit that outputs the result compared with the threshold value of and the line quality detected by these line quality detection circuits is lower than the preset threshold value of the line quality is detected. On the basis of the output of the above, the working line is switched to the protection line in the sending end line switching circuit and the receiving end line switching circuit, and when M or more working lines are switched to the protection line, these working lines are set. From the line having the higher threshold to the Mth working line are preferentially switched to the protection line, and the threshold of the line quality detection circuit of the switched protection line is set to the switched working line. Digital signal transmission method characterized by comprising a line switching control circuit for rewriting the which was value.
JP920489A 1989-01-18 1989-01-18 Digital signal transmission system Expired - Fee Related JPH0787446B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP920489A JPH0787446B2 (en) 1989-01-18 1989-01-18 Digital signal transmission system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP920489A JPH0787446B2 (en) 1989-01-18 1989-01-18 Digital signal transmission system

Publications (2)

Publication Number Publication Date
JPH02190042A JPH02190042A (en) 1990-07-26
JPH0787446B2 true JPH0787446B2 (en) 1995-09-20

Family

ID=11713948

Family Applications (1)

Application Number Title Priority Date Filing Date
JP920489A Expired - Fee Related JPH0787446B2 (en) 1989-01-18 1989-01-18 Digital signal transmission system

Country Status (1)

Country Link
JP (1) JPH0787446B2 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2864847B2 (en) * 1992-01-31 1999-03-08 日本電気株式会社 Line switching system

Also Published As

Publication number Publication date
JPH02190042A (en) 1990-07-26

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