CA2076996C - Transmission line switching devices capable of switching to a redundant system when a failure occurs in the system path - Google Patents
Transmission line switching devices capable of switching to a redundant system when a failure occurs in the system pathInfo
- Publication number
- CA2076996C CA2076996C CA 2076996 CA2076996A CA2076996C CA 2076996 C CA2076996 C CA 2076996C CA 2076996 CA2076996 CA 2076996 CA 2076996 A CA2076996 A CA 2076996A CA 2076996 C CA2076996 C CA 2076996C
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- CA
- Canada
- Prior art keywords
- signal
- channel
- node
- transmission line
- ring network
- 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
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Abstract
A transmission line switching device built into each of a plurality of nodes which connect a transmission line in a ring network configuration. The switching device has a matrix switch 30 for changing the conductive state of a node such that signals being transmitted through the ring network are either transmitted through the node or terminated at the node.
Loopback switches, which are separated from the matrix switch, change the conductive state of the node such that a loopback connection is configured to recover the transmission path of the ring network when a failure occurs in a section of the ring network.
Loopback switches, which are separated from the matrix switch, change the conductive state of the node such that a loopback connection is configured to recover the transmission path of the ring network when a failure occurs in a section of the ring network.
Description
~~'~~99 TRANSMISSION LINE SWITCHING DEVICES
BACKGROUND OF THE INVENTION
The present invention relates to transmission line switching devices provided in respective nodes in a ring transmission line configuration.
As shown in Fig. 4, a conventional transmission line switching device at a node has a matrix switch 70 set therein that controls and switches the circuit such that the circuit either passes through the node or is terminated at the node.
Also, in case of switching to a redundant system for failure restoration in a transmission line, the control of switching to a redundant system is performed by controlling the matrix switch 70 so as to turn back the received signal.
Switching to a redundant system for failure restoration is required to be made at high speed in order to minimize as much as possible the failure time in the transmission line. On the other hand, switching the circuit to pass through the node or to be terminated at the node for network configuration is usually only performed, if at all, at the time circuits are installed and service is started.
Hut, since the conventional transmission equipment uses matrix switches, it is suited for network configuration from the view point of the degrees of freedom provided. However, the control procedure of the matrix switch was complicated so that the conventional equipment was not generally suitable for cases requiring emergency switching of the transmission line to a redundant system.
The present invention overcomes the above mentioned problems. It is an object of the present invention to provide a transmission line switching device which is capable of switching to a redundant system with a simple control and the switching to perform at high speed when a failure occurs in a transmission path.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram of a transmission line switching device as one embodiment of the present invention.
Fig. 2 is a block diagram of a ringed transmission system to which the inventive transmission line switching device is applied.
Fig. 3 illustrates the switching operation of the ringed transmission system of Fig. 2 performed when a trouble occurs in the transmission line.
Fig. 4 is a block diagram of a conventional transmission line switching device.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a transmission line switching device built into each of a plurality of nodes which connect to transmission lines in a ring network configuration, comprising: a matrix switch for switching a conductive state of a node such that signals transmitted through the ring network are either transmitted through the node or terminated at the node; and a loopback switch separated from the matrix switch for switching the conductive state of the node such that a loopback connection is configured to recover a transmission path of the ring network when a failure occurs in a section of the ring ~~' W
BACKGROUND OF THE INVENTION
The present invention relates to transmission line switching devices provided in respective nodes in a ring transmission line configuration.
As shown in Fig. 4, a conventional transmission line switching device at a node has a matrix switch 70 set therein that controls and switches the circuit such that the circuit either passes through the node or is terminated at the node.
Also, in case of switching to a redundant system for failure restoration in a transmission line, the control of switching to a redundant system is performed by controlling the matrix switch 70 so as to turn back the received signal.
Switching to a redundant system for failure restoration is required to be made at high speed in order to minimize as much as possible the failure time in the transmission line. On the other hand, switching the circuit to pass through the node or to be terminated at the node for network configuration is usually only performed, if at all, at the time circuits are installed and service is started.
Hut, since the conventional transmission equipment uses matrix switches, it is suited for network configuration from the view point of the degrees of freedom provided. However, the control procedure of the matrix switch was complicated so that the conventional equipment was not generally suitable for cases requiring emergency switching of the transmission line to a redundant system.
The present invention overcomes the above mentioned problems. It is an object of the present invention to provide a transmission line switching device which is capable of switching to a redundant system with a simple control and the switching to perform at high speed when a failure occurs in a transmission path.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a block diagram of a transmission line switching device as one embodiment of the present invention.
Fig. 2 is a block diagram of a ringed transmission system to which the inventive transmission line switching device is applied.
Fig. 3 illustrates the switching operation of the ringed transmission system of Fig. 2 performed when a trouble occurs in the transmission line.
Fig. 4 is a block diagram of a conventional transmission line switching device.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a transmission line switching device built into each of a plurality of nodes which connect to transmission lines in a ring network configuration, comprising: a matrix switch for switching a conductive state of a node such that signals transmitted through the ring network are either transmitted through the node or terminated at the node; and a loopback switch separated from the matrix switch for switching the conductive state of the node such that a loopback connection is configured to recover a transmission path of the ring network when a failure occurs in a section of the ring ~~' W
network .
In detail, clockwise signals and counterclockwise signals are transmitted through a plurality of channels of the ring transmission line. Each of the channels includes a first-channel signal and a second-channel signal. The first channel signal is a main signal when the whole transmission system is normally working.
A first demultiplexer (401) demultiplexes the received clockwise signal into a received first-channel signal and a received second-channel signal. A second demultiplexer (402) demultiplexes the received counterclockwise signal to a received first-channel signal and a received second-channel signal. A first multiplexes (501) multiplexes a first-channel and a second-channel counterclockwise transmission signals to a transmitted counterclockwise signal. A second multiplexes (502) multiplexes a first-channel and a second-channel clockwise transmission signals to a transmitted clockwise signal.
A matrix switch (30) switches between a transmission state and a termination state. The transmission state is such that a first-channel corresponding signal and a second-channel corresponding signal to the first-channel received signal and the second-channel received signal respectively are clockwise and counterclockwise passed through the matrix switch as a first-channel pass signal and a second-channel pass signal, respectively. The terminating state is such that the clockwise and the counterclockwise first-channel corresponding - 4 - 20 ~s9 9 s signals as the clockwise and the counterclockwise first-channel received signals are terminated at the concerned node.
Pattern generators (641, 642) generate idle signal patterns. Pattern switching circuits (631, 632) send the idle pattern to the second-channels in the ring network clockwise and counterclockwise when the whole transmission system is normally working.
First switching circuits (621, 611) switch from the first-channel and the second-channel counterclockwise pass signals through the matrix switch to the second-channel and the first-channel clockwise corresponding signals, respectively, to be outputted to the matrix switch.
Second switching circuits (622, 612) switch from the first-channel and the second-channel clockwise pass signals through the matrix switch to the second-channel and the first-channel counterclockwise corresponding signals, respectively, to be outputted to the matrix switch.
When a fault or disconnection occurs in the transmission line connecting two nodes, one of the two nodes operates one of the first and second switching circuits and the other node operates the other switching circuit, resulting in a loopback connection to recover communication paths.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described hereinafter with reference to the accompanying drawings.
In detail, clockwise signals and counterclockwise signals are transmitted through a plurality of channels of the ring transmission line. Each of the channels includes a first-channel signal and a second-channel signal. The first channel signal is a main signal when the whole transmission system is normally working.
A first demultiplexer (401) demultiplexes the received clockwise signal into a received first-channel signal and a received second-channel signal. A second demultiplexer (402) demultiplexes the received counterclockwise signal to a received first-channel signal and a received second-channel signal. A first multiplexes (501) multiplexes a first-channel and a second-channel counterclockwise transmission signals to a transmitted counterclockwise signal. A second multiplexes (502) multiplexes a first-channel and a second-channel clockwise transmission signals to a transmitted clockwise signal.
A matrix switch (30) switches between a transmission state and a termination state. The transmission state is such that a first-channel corresponding signal and a second-channel corresponding signal to the first-channel received signal and the second-channel received signal respectively are clockwise and counterclockwise passed through the matrix switch as a first-channel pass signal and a second-channel pass signal, respectively. The terminating state is such that the clockwise and the counterclockwise first-channel corresponding - 4 - 20 ~s9 9 s signals as the clockwise and the counterclockwise first-channel received signals are terminated at the concerned node.
Pattern generators (641, 642) generate idle signal patterns. Pattern switching circuits (631, 632) send the idle pattern to the second-channels in the ring network clockwise and counterclockwise when the whole transmission system is normally working.
First switching circuits (621, 611) switch from the first-channel and the second-channel counterclockwise pass signals through the matrix switch to the second-channel and the first-channel clockwise corresponding signals, respectively, to be outputted to the matrix switch.
Second switching circuits (622, 612) switch from the first-channel and the second-channel clockwise pass signals through the matrix switch to the second-channel and the first-channel counterclockwise corresponding signals, respectively, to be outputted to the matrix switch.
When a fault or disconnection occurs in the transmission line connecting two nodes, one of the two nodes operates one of the first and second switching circuits and the other node operates the other switching circuit, resulting in a loopback connection to recover communication paths.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described hereinafter with reference to the accompanying drawings.
Referring to Figs. 1 and 2, a transmission line switching device according to the present invention is equipped with signal demultiplexers 401 and 402 and signal multiplexers 501 and 502. The signal demultiplexer 401 separates the received clockwise signal of the ring network into a first-channel (hereinafter referred to as 0-channel) signal and a second-channel (hereinafter referred to as 1-channel) signal, and the signal demultiplexer 402 separates the received counterclockwise signal into 0-channel and 1-channel signals. The signal multiplexes 501 multiplexes 0-channel and 1-channel input signals into a transmitted counterclockwise signal, and the signal multiplexes 502 multiplexes 0-channel and 1-channel input signals into a transmitted clockwise signal.
The matrix switch 30 switches between a transmission state and a termination state. The transmission state is such that a 0-channel corresponding signal to the received 0-channel signal and a 1-channel corresponding signal to the received 1-channel signal are clockwise and counterclockwise passed through the matrix switch 30 as a 0-channel pass signal and a 1-channel pass signal respectively. The termination state is such that the clockwise and counterclockwise 0-channel corresponding signals as the clockwise and the counterclockwise received 0-channel signals are terminated at the node.
The pattern generators 641 and 642 generate idle signal patterns and the pattern switching circuits 631 and 632 ~'~' ~ 66446-547 send the idle pattern to the 1-channels of the ring network clockwise and counterclockwise when the whole transmission system is normally working.
The switching circuits 621 and 611 switch from the 0-channel and the 1-channel counterclockwise pass signals through the matrix switch to the 1-channel and the 0-channel clockwise corresponding signals, respectively, to be outputted to the matrix switch.
The switching circuits 622 and 612 switch from the 0-channel and the 1-channel clockwise pass signals through the matrix switch to the 1-channel and the 0-channel counterclockwise corresponding signals, respectively, to be outputted to the matrix switch.
The operation of the transmission line switching device with such a structure will be described below. Fig. 3 illustrates a switching operation performed when a failure occurs in the ring network to which the transmission line switching device of the present invention is applied.
In Fig. 2, a plurality of nodes 201-204 are provided in the ring network. A plurality of signal channels are multiplexed in the transmission line of the ring network and each multiplexed signal channel respectively contains 0-channel and 1-channel signals. To simplify the explanation, Fig. 2 illustrates the 0-channel and the 1-channel signals of a particular channel.
Circuit connections are made selectively so as to connect any two nodes in the ring network. In Fig. 2, circuit _ 7 -configuration is shown when the transmission path 11 connects the node 201 and the node 202 via the nodes 203 and 204 and when the transmission path 12 connects the nodes 201 and 202.
Normally, when the overall transmission system is properly working, signals are transmitted through the 0-channel and the transmission path is connected so as to provide a path as shown by the solid line in Fig. 2. On the other hand, since the 1-channel is not carrying any signals at this time, there is no way nodes can determine whether the 1-channel is normal or abnormal. When a failure occurs in the 0-channel, it is reguired to immediately switch to the 1-channel signal transmission. Therefore, the operating state of the 1-channel signal must be in a state such that the switching control system can determine its state at any time. For this purpose, the transmission line switching device of each node includes a normal signal pattern generator for sending a normal signal pattern to the 1-channel when the transmission system is working. Such a normal signal pattern is called an idle pattern. The idle pattern is generated by the pattern generators (PG) 641 and 642 (shown in Fig. 1} built into each transmission line switching device.
The reconfiguration which takes place when a failure has occurred in the transmission system will be described below with reference to Fig. 3, which shows the situation where the transmission line is severed between the nodes 203 and 204. The recovery of the transmission path is performed by turning back the 0-channel signal to the 1-channel signal ;,'.
20 ~s9 s s _8_ and the 1-channel signal to the 0-channel signal at the two end nodes of the circuit section of the transmission path in which the failure has occurred. In this case, the signal to be transmitted from the node 201 to the node 202 through the transmission path 11 is temporarily transmitted as a counterclockwise signal from the node 201 to the node 204 where the signal is cut over to the clockwise 1-channel signal which is then transmitted through the nodes 201, 202 and 203.
At the node 203, this signal is again cut over to the counterclockwise 0-channel signal which finally arrives at the node 202. The signal to be transmitted from the node 20~ to the node 201 through the transmission path 11 follows the reverse route to that mentioned above. Also during such situation, the transmission switching device of each node is in what is called a through state where it does not transmit the idle pattern in the 1-channel but transmits the received 1-channel signal as it is.
As described above, the method of recovering the transmission path is characterized by turning back the transmission signal at the nodes at both ends of the section of the path in which a failure has occurred without any necessity of changing the circuit configuration at the nodes 201 and 202.
Now, when a failure occurs downstream in the clockwise transmission line using the conventional transmission device as shown in Fig. 4, a reconfiguration operation takes place such that turn back paths 100 and 110 _ g _ for the clockwise signals, shown by the line with one dash, are connected and the connection paths 120 and 121 with the fed idle patterns in the 1-channel are changed to a through connection and made to pass the turn back signal. Generally, a matrix switch can arbitrarily select the input and output of signals and from the standpoint of operational freedom, the above mentioned modification of the network configuration can be considered possible. However, when a failure occurs in the transmission path, all circuits that share this transmission line requires reconfiguration, and it is considered to be difficult to recover the circuit in a very short time.
As shown in Fig. 1, in the transmission device of the present invention, the signal switching device and the matrix switch are separated from each other. Therefore, it has the characteristics that the control of switching to a redundant system for recovering the network is performed by the signal switching device while the network configuration such that a transmission path is terminated or non-terminated is performed by the matrix switch. For example, when a failure occurs downstream in the clockwise transmission line similarly to the above-mentioned case, turn back is performed by the switching circuits 622 and 612 that cut over the clockwise signal to a counterclockwise signal. On the other hand, when the transmission system is normally working, the idle pattern generated by the pattern generator 641 is fed into the 1-channel signal and transmitted while the switching circuit 631 provides a through connection when a failure ~o ~s9 9 s occurs in the transmission path. As described above, switching to a redundant system due to a failure in the transmission path can be performed only by the switching device and it is not necessary to modify any of the network configuration of the matrix switch. The connection paths 130 and 131 shown by the line with two dashes in Fig. 1 illustrate the state of the network configuration when the node in which the transmission device of the present invention is provided does not terminate the path and requires the path to pass through the node.
As described above, the present invention provides the superior capability of switching to a redundant system by a simple control at high speed when a failure occurs in the transmission path.
The matrix switch 30 switches between a transmission state and a termination state. The transmission state is such that a 0-channel corresponding signal to the received 0-channel signal and a 1-channel corresponding signal to the received 1-channel signal are clockwise and counterclockwise passed through the matrix switch 30 as a 0-channel pass signal and a 1-channel pass signal respectively. The termination state is such that the clockwise and counterclockwise 0-channel corresponding signals as the clockwise and the counterclockwise received 0-channel signals are terminated at the node.
The pattern generators 641 and 642 generate idle signal patterns and the pattern switching circuits 631 and 632 ~'~' ~ 66446-547 send the idle pattern to the 1-channels of the ring network clockwise and counterclockwise when the whole transmission system is normally working.
The switching circuits 621 and 611 switch from the 0-channel and the 1-channel counterclockwise pass signals through the matrix switch to the 1-channel and the 0-channel clockwise corresponding signals, respectively, to be outputted to the matrix switch.
The switching circuits 622 and 612 switch from the 0-channel and the 1-channel clockwise pass signals through the matrix switch to the 1-channel and the 0-channel counterclockwise corresponding signals, respectively, to be outputted to the matrix switch.
The operation of the transmission line switching device with such a structure will be described below. Fig. 3 illustrates a switching operation performed when a failure occurs in the ring network to which the transmission line switching device of the present invention is applied.
In Fig. 2, a plurality of nodes 201-204 are provided in the ring network. A plurality of signal channels are multiplexed in the transmission line of the ring network and each multiplexed signal channel respectively contains 0-channel and 1-channel signals. To simplify the explanation, Fig. 2 illustrates the 0-channel and the 1-channel signals of a particular channel.
Circuit connections are made selectively so as to connect any two nodes in the ring network. In Fig. 2, circuit _ 7 -configuration is shown when the transmission path 11 connects the node 201 and the node 202 via the nodes 203 and 204 and when the transmission path 12 connects the nodes 201 and 202.
Normally, when the overall transmission system is properly working, signals are transmitted through the 0-channel and the transmission path is connected so as to provide a path as shown by the solid line in Fig. 2. On the other hand, since the 1-channel is not carrying any signals at this time, there is no way nodes can determine whether the 1-channel is normal or abnormal. When a failure occurs in the 0-channel, it is reguired to immediately switch to the 1-channel signal transmission. Therefore, the operating state of the 1-channel signal must be in a state such that the switching control system can determine its state at any time. For this purpose, the transmission line switching device of each node includes a normal signal pattern generator for sending a normal signal pattern to the 1-channel when the transmission system is working. Such a normal signal pattern is called an idle pattern. The idle pattern is generated by the pattern generators (PG) 641 and 642 (shown in Fig. 1} built into each transmission line switching device.
The reconfiguration which takes place when a failure has occurred in the transmission system will be described below with reference to Fig. 3, which shows the situation where the transmission line is severed between the nodes 203 and 204. The recovery of the transmission path is performed by turning back the 0-channel signal to the 1-channel signal ;,'.
20 ~s9 s s _8_ and the 1-channel signal to the 0-channel signal at the two end nodes of the circuit section of the transmission path in which the failure has occurred. In this case, the signal to be transmitted from the node 201 to the node 202 through the transmission path 11 is temporarily transmitted as a counterclockwise signal from the node 201 to the node 204 where the signal is cut over to the clockwise 1-channel signal which is then transmitted through the nodes 201, 202 and 203.
At the node 203, this signal is again cut over to the counterclockwise 0-channel signal which finally arrives at the node 202. The signal to be transmitted from the node 20~ to the node 201 through the transmission path 11 follows the reverse route to that mentioned above. Also during such situation, the transmission switching device of each node is in what is called a through state where it does not transmit the idle pattern in the 1-channel but transmits the received 1-channel signal as it is.
As described above, the method of recovering the transmission path is characterized by turning back the transmission signal at the nodes at both ends of the section of the path in which a failure has occurred without any necessity of changing the circuit configuration at the nodes 201 and 202.
Now, when a failure occurs downstream in the clockwise transmission line using the conventional transmission device as shown in Fig. 4, a reconfiguration operation takes place such that turn back paths 100 and 110 _ g _ for the clockwise signals, shown by the line with one dash, are connected and the connection paths 120 and 121 with the fed idle patterns in the 1-channel are changed to a through connection and made to pass the turn back signal. Generally, a matrix switch can arbitrarily select the input and output of signals and from the standpoint of operational freedom, the above mentioned modification of the network configuration can be considered possible. However, when a failure occurs in the transmission path, all circuits that share this transmission line requires reconfiguration, and it is considered to be difficult to recover the circuit in a very short time.
As shown in Fig. 1, in the transmission device of the present invention, the signal switching device and the matrix switch are separated from each other. Therefore, it has the characteristics that the control of switching to a redundant system for recovering the network is performed by the signal switching device while the network configuration such that a transmission path is terminated or non-terminated is performed by the matrix switch. For example, when a failure occurs downstream in the clockwise transmission line similarly to the above-mentioned case, turn back is performed by the switching circuits 622 and 612 that cut over the clockwise signal to a counterclockwise signal. On the other hand, when the transmission system is normally working, the idle pattern generated by the pattern generator 641 is fed into the 1-channel signal and transmitted while the switching circuit 631 provides a through connection when a failure ~o ~s9 9 s occurs in the transmission path. As described above, switching to a redundant system due to a failure in the transmission path can be performed only by the switching device and it is not necessary to modify any of the network configuration of the matrix switch. The connection paths 130 and 131 shown by the line with two dashes in Fig. 1 illustrate the state of the network configuration when the node in which the transmission device of the present invention is provided does not terminate the path and requires the path to pass through the node.
As described above, the present invention provides the superior capability of switching to a redundant system by a simple control at high speed when a failure occurs in the transmission path.
Claims (4)
1. A transmission line switching device built into each of a plurality of nodes which connect to transmission lines in a ring network configuration, comprising:
a matrix switch for switching a conductive state of a node such that signals transmitted through the ring network are either transmitted through the node or terminated at the node; and a loopback switch separated from the matrix switch for switching the conductive state of the node such that a loop-back connection is configured to recover a transmission path of the ring network when a failure occurs in a section of the ring network.
a matrix switch for switching a conductive state of a node such that signals transmitted through the ring network are either transmitted through the node or terminated at the node; and a loopback switch separated from the matrix switch for switching the conductive state of the node such that a loop-back connection is configured to recover a transmission path of the ring network when a failure occurs in a section of the ring network.
2. A transmission line switching device according to claim 1 in which the loopback switch switches a signal transmission direction from the signal's initial direction to its opposite direction in the ring network at each of two nodes adjacent to a section of the ring network in which a failure has occurred.
3. A transmission lines switching device according to claim 1 in which the loopback switch is comprised of a first signal switching means and a second signal switching means which are connected to the matrix switch.
4. A transmission line switching device according to claim 1 further comprising:
a standby channel within the ring network; and a pulse generator connected to the standby channel for the monitoring thereof.
a standby channel within the ring network; and a pulse generator connected to the standby channel for the monitoring thereof.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP217577/1991 | 1991-08-28 | ||
| JP21757791A JP2697395B2 (en) | 1991-08-28 | 1991-08-28 | Transmission line switching device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2076996A1 CA2076996A1 (en) | 1993-03-01 |
| CA2076996C true CA2076996C (en) | 1999-12-07 |
Family
ID=16706463
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2076996 Expired - Fee Related CA2076996C (en) | 1991-08-28 | 1992-08-27 | Transmission line switching devices capable of switching to a redundant system when a failure occurs in the system path |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JP2697395B2 (en) |
| CA (1) | CA2076996C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101600217B (en) * | 2008-06-04 | 2012-09-05 | 日本电气株式会社 | Transmission network, transmission device, channel switching method of transmission network and program thereof |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07162903A (en) * | 1993-12-08 | 1995-06-23 | Nec Corp | Terminal equipment |
| TW353838B (en) | 1996-11-12 | 1999-03-01 | Toshiba Corp | Ring network system and control method of its communication path |
-
1991
- 1991-08-28 JP JP21757791A patent/JP2697395B2/en not_active Expired - Fee Related
-
1992
- 1992-08-27 CA CA 2076996 patent/CA2076996C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101600217B (en) * | 2008-06-04 | 2012-09-05 | 日本电气株式会社 | Transmission network, transmission device, channel switching method of transmission network and program thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0563601A (en) | 1993-03-12 |
| CA2076996A1 (en) | 1993-03-01 |
| JP2697395B2 (en) | 1998-01-14 |
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