JP4662652B2 - Line switching method in SDH transmission system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a line switching method in an SDH (synchronous digital hierarchy) transmission system.
[0002]
[Prior art]
A configuration example of a line switching apparatus of a conventional SDH transmission system is shown in FIG. For convenience of explanation, in the figure, only the transmitting end portion is shown on the A station side, and only the receiving end portion is shown on the B station side.
[0003]
This line switching apparatus is provided for switching between a working line N line and a (1 + N) line of one protection line, and is configured by combining line monitoring apparatuses 1A and 1B. The line monitoring apparatuses 1A and 1B perform line information and switching control for each line. Since the same line in each system has the same function, the following explanation of the working line will be made taking the working system 1 as an example.
[0004]
The working line 1 includes a sending end code processing unit 201, a receiving end code processing unit 301, an AIS INS unit 401, a receiving end signal switching unit 601, and an OR circuit 701. For the sending end, the sending end code processing unit 201 generates an SDH frame and inserts OH (overhead) and sends it to the work line 1. As for the receiving end unit, the receiving end code processing unit 301 synchronizes the frames and separates the OH and sends it to the AIS INS unit 401.
[0005]
The AIS INS unit 401 has an AIS (ALM Indicate Signal, alarm display signal) insertion function, and when a disconnection detection signal is transmitted due to a failure detected by the receiving end signal processing unit 301, an AIS is inserted into the main signal. Then, it is sent to the receiving end signal switching unit 601.
[0006]
The receiving signal switching unit 601 has a signal switching function, and switches between a signal on the working line side and a signal on the protection line side. The switching control is performed from the line monitoring apparatus 1B via the receiving end signal distribution unit 500, and outputs a signal according to the switching control instruction.
[0007]
Further, the switching control to the receiving end signal switching unit 601 can be performed not only automatically as described above, but also when automatic line switching is disabled due to a failure of the line monitoring device or the like. Each active system is provided with a forcible switch. In the OR circuit 701, the control from the receiving end signal distribution unit 500 and the control of the forcible switch are logically summed, and switching is also possible by the forcible control.
[0008]
The protection line includes a transmission end code processing unit 200, a reception end code processing unit 300, an AIS INS unit 400, a transmission end signal switching unit 100, and a reception end signal switching unit 500.
[0009]
In the transmission end signal switching unit 100, a signal branched from each active system is selected by a control instruction from the line monitoring apparatus 1A, and is transmitted to the transmission end code processing unit 200. Thereafter, the signal is sent from the sending end processing unit 200 to the receiving end signal distribution unit 500 via the receiving end code processing unit 300 and the AIS INS unit 400. This point is processed in the same operation as the current system.
[0010]
The protection line signal transmitted from the AIS INS unit 400 is distributed to the receiving end signal switching unit (for example, the receiving end signal switching unit 601 in the case of the active system 1) in the receiving end signal distribution unit 500. . Thereafter, the signal operates in the receiving end signal switching unit in the same manner as described for the active system, and the switching is completed.
[0011]
As described above, at the receiving end of the line switching device, when the input signal from the opposite station is in an abnormal state due to a failure or disconnection in the AIS INS unit configured in each system, it is unknown to the subsequent system ( AIS is inserted so as not to send data (low reliability).
[0012]
On the other hand, conventionally, various techniques using unused bytes or undefined bytes have been proposed for SDH transmission systems.
[0013]
For example, Japanese Patent Application Laid-Open No. 11-284591 relates to a monitoring signal transmission method of an SDH transmission system by transferring an image signal using an undefined byte Z1 byte in addition to transferring an audio signal using E1 and E2 bytes. A technique that enables quick recovery work is disclosed.
[0014]
Further, in the SDH transmission system and the alarm transmission control method described in Japanese Patent Laid-Open No. 10-145321, in the alarm transmission control method in a plurality of network devices, undefined bytes are used, and alarms other than existing data communication channels are used. The importance level is transmitted to the network management apparatus, whereby an alarm with a high degree of urgency can be preferentially transferred to the network management apparatus, and the occurrence of the alarm can be notified to the network manager in a short time.
[0015]
Furthermore, in the audio signal transmission / reception method for meeting described in Japanese Patent Laid-Open No. 10-164110, in a transmission apparatus in which a plurality of stations are configured in a loop by a 0/1 system transmission line using SDH, audio for meeting each station By inserting a signal into an unused byte assigned to each station and transferring the signal, even if a failure occurs in one transmission path, a call can be made in all stations using the other transmission path.
[0016]
Japanese Patent Laid-Open No. 9-275383 discloses that in an SDH wireless transmission system, an auxiliary signal is transmitted using undefined bytes of SOH (section overhead), thereby generating no wireless overhead for the auxiliary signal. In other words, a technique for improving the transmission efficiency by preventing the expansion of the occupied band has been disclosed.
[0017]
Further, the technique described in Japanese Patent Laid-Open No. 5-316133 relates to a monitoring control system that collects alarm information and the like through a data communication channel (DCC) and remotely monitors the ring network, and when the line disconnection is detected, Remote centralized monitoring is possible by changing the service of each node in the ring using the used bytes and automatically resetting the route of the data communication channel.
[0018]
In addition, the data transmission method described in Japanese Patent Laid-Open No. 5-56023 is a data transmission method in a loop network in which one master station device and N slave station devices are connected in a loop shape. By inserting a multi-frame identification signal, it is possible to process in units of a plurality of frames in the STM-1 frame format.
[0019]
[Problems to be solved by the invention]
However, in the conventional line switching apparatus shown in FIG. 3, even if the connection between each line is wrong, the passing signal is only a signal on a different line. Etc. are not detected, and incorrect connection cannot be recognized. As a result, the abnormal state cannot be detected, the AIS insertion function does not work despite the signal on the wrong line, the input signal is sent to the subsequent system as it is, and the signal on the different line is received in the subsequent system. There was a problem of becoming.
[0020]
For example, even when the sending end output of the working system 2 is erroneously connected to the receiving end input of the working system 1, the receiving end code processing unit 301 does not mean that the input signal does not exist, so input disconnection is not detected, Also, since there is no line recognition function, the signal of the working system 1 is output as it is via the receiving signal switching unit 601 and the signal of the working system 2 is output to the output to which the signal of the working system 1 should be sent. Therefore, the latter system has a problem that information is leaked by receiving a line of a different system.
[0021]
Line switching is based on the premise that the same system is controlled to be switched between the sending end side and the receiving end side of the corresponding active system to be bypassed to the protection line. When the forcible change-over switch on the receiving end side is controlled, there is a problem that the system sends line information of a different system to the subsequent system and information is leaked.
[0022]
For example, when the line of the working system 1 is switched (the signal of the working system bypasses the protection system and the protection line), the receiving end signal switching unit 601 of the working system 1 receives the receiving end signal distribution. The signal from the part 500 side is selected and output. Further, the same signal of the working system 1 is also inputted to the standby side input of the receiving end signal switching unit 602 of the working system 2. At this time, if the forcible control of the active system 2 is activated due to an erroneous operation, the receiving end signal switching unit 602 selects the signal from the receiving end signal distributing unit 500 (the signal of the active system 1 is currently input). To do. As a result, the receiving end signal switching unit 602 outputs the signal of the working system 1, and there is a problem that the signal of the working system 1 is output to the output to which the signal of the working system 2 should be sent. To do. Further, since the system at the subsequent stage receives signals on different lines, there is a problem that information leaks.
[0023]
On the other hand, the technology described in each of the above patent publications is a technology using an unused byte or an undefined byte, but in any technology, it is not used to prevent information leakage. The problem cannot be solved.
[0024]
Accordingly, the present invention has been made in view of the problems in the above-described conventional line switching apparatus, and it is a main object of the present invention to prevent leakage of information to another line due to erroneous connection of the line or erroneous operation in the SDH transmission system. And In addition to the above, an object of the present invention is to detect erroneous connection of lines in an SDH transmission system.
[0025]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 A plurality of working systems each having a working transmission unit and a working receiving unit connected to the working line, and a spare system having a spare transmission unit and a spare receiving unit connected to the spare line, and a predetermined working system is used as the spare system. Switch to In the SDH transmission system, When a line identification code is set for each working system and the predetermined working system is switched to the spare system, the spare transmitting unit identifies the line corresponding to the predetermined working system with respect to the input signal. A code is transmitted to the standby reception unit via the backup line, and the backup reception unit separates the line identification code from the signal received from the backup transmission unit, and the received signal The line identification code is transmitted to each of the plurality of active reception units, and the line identification code received from the standby reception unit by the plurality of active reception units and the line identification code set in the active reception unit And if it matches, the received signal is output. It is characterized by that.
[0028]
Claim 1 According to the described invention, a line identification code is inserted into a signal detoured to the protection line and transmitted, and the signal of the protection line detouring on each active line is compared with the line identification code on the receiving end side and switched. Since it is possible to determine whether or not the system is applicable, it is possible to prevent leakage of information on other lines due to an erroneous operation.
[0029]
Claim 2 The described invention is claimed. 1 As a preferred form of the line switching method in the SDH transmission system described above, the line identification code is inserted into unused bytes or undefined bytes of the section overhead.
[0030]
Claims 3 According to the described invention, as a preferred mode of the line switching method in the SDH transmission system, when a signal indicating a line identification code of a line different from the line is transmitted, an alarm display signal is inserted into the transmitted signal. It is characterized by that.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Next, a specific example of an embodiment of a line switching method in the SDH transmission system according to the present invention will be described with reference to the drawings.
[0032]
FIG. 1 shows an embodiment of an apparatus to which a line switching method according to the present invention is applied. In addition, the component which attached | subjected the same reference number as the component demonstrated in the prior art example of FIG. 3 has a function similar to a prior art example. Since each active system has the same configuration, the configuration of the active system 1 will be described below as an example.
[0033]
The working line 1 includes a transmission end code processing unit 201 at a transmission end, a reception end code processing unit 301, a reception end signal switching unit 601, comparison circuits 901 and 903, an AIS INS circuit 401, 403 and OR circuits 701, 801, and 803.
[0034]
The sending end code processing unit 201 has an OH insertion function as in the conventional example, but uses this OH insertion function to insert a line identification code (hereinafter referred to as “ID”) set for each line. Composed.
[0035]
The comparison circuit has a function of comparing the match / mismatch of the line identification codes and outputting a determination result. The comparison circuit 901 is a circuit provided for the working system, compares the ID value separated by the receiving end code processing unit 301 with the ID set in the own system, and uses the match / mismatch as a determination signal as a logical signal. Send to sum circuit 801. The comparison circuit 903 is a circuit provided for the standby system, compares the ID value separated by the receiving end code processing unit 300 with the ID set in the own system, and uses match / mismatch as a determination signal. The result is sent to the logical sum circuit 803.
[0036]
The logical sum circuit is a circuit having a logical sum function. The logical sum circuit 801 is a circuit provided for the active system, takes a logical sum of the determination signal from the comparison circuit 901 and the disconnection detection signal sent from the receiving end code processing unit 301, and controls the AIS INS circuit 401 to perform AIS control. Send a signal. The logical sum circuit 803 is a circuit provided for the standby system. The logical sum circuit 803 calculates the logical sum of the determination signal from the comparison circuit 903 and the disconnection detection signal sent from the receiving end code processing unit 300, and sends it to the AIS INS circuit 403. Send AIS control signal.
[0037]
The AIS INS unit 401 has the same function as the conventional example, and is arranged on the input side of the receiving end signal switching unit 601, and the AIS INS unit 403 is arranged on the input side of the receiving end signal switching unit 601 on the standby system side. Is done.
[0038]
Other receiving end code processing section 301, OR circuit 701 and receiving end signal switching section 601 have the same configuration as the conventional example.
[0039]
The protection line includes a transmission end code processing unit 200, a reception end code processing unit 300, a transmission end signal control switching unit 101, and a reception end signal distribution unit 500.
[0040]
The sending end signal control switching unit 101 is obtained by adding a function of sending an ID value to the function of the sending end signal switching unit 100 of the conventional example. As for the ID value, the ID value set in each active system is sent to the sending end signal control switching unit 101 in the same manner as the signal, and the sending end signal control switching unit 101 receives switching control from the line monitoring apparatus 1A. ID of the same system as the received system is sent to the sending end code processing unit 200.
[0041]
Next, the operation of the line switching apparatus having the above configuration will be described.
[0042]
First, in describing the operation of the working line, the working system shown in FIG. 2 will be described by taking as an example the case where the ID value of each working line is set to ID value = 1 of the working system 1 and ID value = 2 of the working system 2. This will be described with reference to a configuration example. FIG. 2 is a configuration example when the active system and the standby system are configured in the same manner, and the configuration is different from the embodiment of the present invention shown in FIG. 1, but for the convenience of explanation of the configuration of the active system, FIG. Two configuration examples are used.
In this description, the case where the ID value is transmitted using the undefined byte Z1 will be described as an example.
[0043]
In the working system 1, the sending end code processing unit 201 inserts the set ID value = 1 into the undefined byte Z1 (Z1 = 1) and sends it to the receiving end. Similarly, in the active system 2, the ID value = 2 is inserted into Z1 = 2 and sent to the receiving end.
[0044]
The receiving end code processing unit 301 separates the transmitted undefined byte Z1 and sends it to the comparison circuit 901. The comparison circuit 901 compares the ID value (ID = 1) set in its own system with the Z1 value (Z1 = 1) sent from the receiving end code processing unit 301. Here, since the values of Z1 = 1 and ID = 1 match, the AIS INS unit 401 does not insert the AIS, and the signal is switched from the AIS INS unit 401 to the receiving end signal as in the conventional example. The data is output via the unit 601.
[0045]
The AIS is inserted only when a failure is detected in the receiving end code processing unit 301 as in the conventional example. The operation is performed when the disconnection detection signal from the receiving end code processing unit 301 is logically ORed. The AIS control signal is transmitted to the AIS INS unit 401 via the circuit 801, and the AIS is inserted into the signal in the AIS INS unit 401 that has undergone AIS control, and is output via the receiving end signal switching unit 601. The same operation is performed in the active system 2.
[0046]
Here, the operation when there is a connection error will be described. The operation will be described by taking as an example a case where a connection error is made between the sending end output of the working system 2 as the receiving end input of the working system 1 and the sending end output of the working system 1 as the receiving end input of the working system 2.
[0047]
The transmission end output signal of the working system 2 is output at the transmission end code processing unit 202 of the working system 2 as a signal (Z1 = 2) in which a fixed ID value 2 is inserted into Z1. On the receiving end side of the active system 1 to which the output signal is connected, Z1 = 2 is separated by the receiving end code processing unit 301 and input to the comparison circuit 901.
[0048]
The comparison circuit 901 compares the ID value = 1 of its own system with the separated Z1 = 2, but outputs a comparison signal to the OR circuit 801 as a mismatch because of a mismatch. This information is controlled as an AIS control signal in the AIS INS unit 401 via the OR circuit 801, and AIS is inserted into the signal. Therefore, in the working system 1, the signal with the AIS inserted passes through the circuits after the AIS INS unit 401, and the information of the working system 2 does not leak to the subsequent system of the working system 1.
[0049]
Similarly, in the working system 2, the comparison circuit 902 compares Z1 = 1 separated by the receiving end code processing unit 302 with the set fixed ID value = 2, and the AIS INS unit because of the mismatch. The AIS is inserted in 402, and the signal in which the AIS is inserted is output to the subsequent circuits and the subsequent system, and the information of the active system 1 is not leaked.
[0050]
In this way, the ID values are compared in the comparison circuit, and if they do not match, the AIS insertion is controlled, so that it is possible to prevent signals from different systems from leaking to the subsequent stage.
[0051]
Next, the protection line system will be described with reference to an example in which the active system 1 is switched.
[0052]
As described above, the ID value of the working system 1 = 1 and the ID value = 2 of the working system 2 are used as the ID value, as described above, and the ID value = 0 is assigned to the protection line. Suppose. As described above, FIG. 2 is an example in which the configuration of the standby system is configured in the same manner as the active system.
[0053]
The transmission end signal switching unit 100 is controlled by the line monitoring apparatus 1A so as to output a signal from the active system 1, and sends the signal of the active system 1 to the transmission end code processing unit 200. The sending end code processing unit 200 inserts the fixed ID value = 0 into Z1 and sends it to the receiving end side.
[0054]
The receiving end code processing unit 300 separates the transmitted undefined byte Z1 (Z1 = 0) and sends it to the comparison circuit 900. The comparison circuit 900 compares the ID value (ID = 0) set in its own system with the Z1 value (Z1 = 0) sent from the receiving end code processing unit 300. Here, since the values of Z1 = 0 and ID = 0 match, AIS insertion is not performed in the AIS INS unit 400, and the signal is sent from the AIS INS unit 401 to the working system 1 via the receiving end signal distribution unit 500. To the receiving end signal switching unit 601.
[0055]
The receiving end signal switching unit 601 selects and outputs a signal on the standby system side under control of the line monitoring apparatus 1B via the receiving end signal distributing unit 500. The signal of the working system 1 is output to the subsequent system bypassing the protection line in this way.
[0056]
In this state, the AIS is inserted only when a failure is detected in the receiving end code processing unit 300, as in the conventional example and the current system, and the operation is disconnected from the receiving end code processing unit 300. The detection signal is transmitted as an AIS control signal to the AIS INS unit 400 via the OR circuit 800, and the AIS INS unit 400 that has received the AIS control inserts the AIS into the signal and sends it to the receiving end signal distribution unit 500. The The signal in which the AIS is inserted is output to the subsequent system via the receiving end signal switching unit 601.
[0057]
Here, the operation in the case of erroneous connection as in the active system will be described. The case where the sending end output of the active system 2 is connected to the receiving end input of the standby system due to erroneous connection will be described as an example.
[0058]
As the signal at the transmission end of the active system 1, a signal in which the fixed ID value = 2 is inserted into Z1 is output and input to the reception end code processing unit 300 of the standby system. Since Z1 separated by the receiving end code processing unit 300 is Z1 = 1 and ID = 0 set in the receiving end spare system, the comparison circuit 900 determines a mismatch, and the control signal passes through the OR circuit 800. The signal is sent to the AIS INS unit 400, the AIS is inserted in the AIS INS unit 400, and the signal into which the AIS is inserted is output to the receiving end signal distribution unit 500.
[0059]
In the receiving end signal distribution unit 500, the signal is distributed to the receiving end signal switching unit of each active system. In this case, the signal into which the AIS is inserted is distributed to the receiving end switching unit of each active system. It becomes. Therefore, in the case of this example, the receiving end signal switching unit of the switching target system outputs a signal with the AIS inserted even if the receiving end signal switching unit 601 switches to the protection line side. Become. This can prevent information from leaking.
[0060]
Next, the operation will be described by taking as an example a case where an erroneous operation is performed in a state where the connection is normally performed and the line is normally switched.
[0061]
For example, in the same manner as described above, the active system 1 is switched to the protection line. At this time, the switching operation of the working system 1 is similar to the above in that the ID is 0 at the sending end / receiving end of the standby system, and the receiving end signal distributor 500 does not insert the AIS and the active end is inserted. The signal of the system 1 is sent to each receiving end signal switching unit.
[0062]
Since the receiving end signal switching unit 601 is controlled to be switched from the line monitoring apparatus 1B via the receiving end signal distributing unit 500, a signal from the receiving end signal distributing unit 500, that is, a signal of the active system 1 is output. Thus, the line switching of the active system 1 is completed.
[0063]
Up to this point, the operation is a normal operation, but in this state, the operation when the forced control is performed in the active system 2 (that is, when an erroneous operation is performed) will be considered.
[0064]
When the line switching of the working system 1 is performed, the signal of the working system 1 is input to the receiving end signal switching unit of each working system. Naturally, the signal of the working system 1 is inputted to the standby system side input of the receiving end signal switching unit 602 of the working system 2.
[0065]
Here, in the active system 2, when forced control (erroneous operation) is performed, the receiving end signal switching unit 602 is controlled via the OR circuit 701 to forcibly select the standby system side, and output In this case, the signal of the active system 1 is output. That is, the signal of the working system 1 is output to the output of the working system 2. In this way, information on different lines is leaked due to an erroneous operation.
[0066]
Therefore, the standby system needs to be configured differently from the current system. FIG. 1 shows a configuration of the present invention in which the configurations of the active system and the standby system are different.
[0067]
In the configuration of the present invention, the comparison circuit 900 and the OR circuit 800 and the AIS INS circuit 400 which are configured as a backup system in FIG. 2 are configured before the receiving signal switching unit of each active system, and the transmitting signal switching is performed. The terminal 100 receives a fixed ID value from each active system in the unit 100 and, under the control of the line switching device 1A, adds a function to send the ID value of the corresponding system to the transmission end code processing unit 200. 101 is configured. The operation of the signal from the sending end input to the receiving end side signal switching unit in the active system is the same as described so far.
[0068]
The operation of the configuration of the spare system of the present invention that prevents information leakage will be described below.
[0069]
In the first place, the sending end signal control switching unit 101 controls the system to be switched from the line monitoring apparatus 1A and recognizes which system is switched to select. Therefore, the sending end signal control switching unit 101 collects the line identification code information set in each active system, and sends the ID value of the system corresponding to the switching control from the line switching device 1A to the sending end code processing unit 200. To do.
[0070]
For example, assuming that the same ID as described above is set, when the working system 1 is switched, the ID value = 1 of the working system 1 is sent to the transmitting end code processing unit 200. For example, when the working system 2 is switched, ID = 2 is sent to the transmission end code processing unit 200.
[0071]
The sending end code processing unit 200 inserts the ID value from the sending end signal control switching unit 101 into an unused byte or an undefined byte, and sends a signal to the receiving end side. The receiving end code processing unit 300 separates the ID value from the unused bytes or undefined bytes of the transmitted signal and sends it to the comparison circuit for the protection line configured in each active system. In the comparison circuit, the line identification code of the own system is compared with the ID value transmitted from the standby system, and inserted into the AIS INS circuit via an OR circuit configured for the backup system. The operations of each comparison circuit, logical sum circuit, and AIS INS circuit are the same as described above.
[0072]
In the following, the operation in a state in which the active system 1 is switched to the protection line as described in the example at the time of the previous erroneous operation will be described. The ID values are set such that the working system 1 is set to ID = 1 and the working system 2 is set to ID = 2 as described above.
[0073]
Under control from the line switching apparatus 1A, the sending end signal control switching unit 101 selects the working system 1 and sends it to the sending end code processing unit 200. At the same time, the ID value = 1 of the working system is also sent to the sending end code processing unit 200. Send it out. The sending end code processing section 200 inserts ID value = 1 sent from the sending end signal control switching section 101 into Z1, and sends it to the receiving end section. The receiving end code processing unit 300 separates Z1 = 1 where ID value information is inserted from the transmitted signal.
[0074]
The comparison circuit 903 for the protection line of the working system 1 compares the ID value = 1 of the own system with Z1 = 1 sent from the receiving end code processing unit 300 of the protection system, and ID = 1 and Z1 = 1. Find a match. Since the ID values match, the AIS INS unit 403 provided for the standby system of the active system 1 outputs a signal to the receiving end signal switching unit 601 without inserting the AIS.
[0075]
At this time, when forcible control is performed in the working system 2, the protection line comparison circuit 904 of the working system 2 sends the ID value = 2 of the own system and the receiving end code processing unit 300 of the protection system. Z1 = 1 is compared, ID = 2 and Z1 = 1 do not match, and the determination signal is sent to the OR circuit 804 as a mismatch. The AIS INS unit 404 performs AIS control via the OR circuit 804, and sends a signal with the AIS inserted to the receiving end signal switching unit 602. The receiving end signal switching unit 602 outputs a signal on the standby system side. However, since the AIS is already inserted into the signal of the active system 1, information on different lines does not leak.
[0076]
In the above-described embodiment, the line identification code is transmitted using the undefined byte Z1 of the SOH. However, the same effect can be obtained by using an unused byte in addition to the undefined byte. can get.
[0077]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent leakage of information to another line due to erroneous connection or erroneous operation of the SDH transmission system, and to detect erroneous connection of the line. A line switching method in a transmission system can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of a line switching apparatus to which a line switching method according to the present invention is applied.
FIG. 2 is a block diagram showing an embodiment of an active system of a line switching apparatus to which a line switching method according to the present invention is applied.
FIG. 3 is a block diagram showing an example of a conventional line switching apparatus.
[Explanation of symbols]
1A Line monitoring device (A station)
1B Line monitoring device (B station)
2A A station line switching device
2B B station line switching device
100 Sending end signal switching part
101 Sending end signal control switching unit
200, 201, 202 Sending end code processing unit
300, 301, 302 Receiving end code processing unit
400, 401, 402, 403, 404 AIS INS section
501 Receiver signal distribution unit
601 and 602 receiving end signal switching unit
701, 702 OR circuit (for switching control)
800, 801, 802, 803, 804 OR circuit (for AIS control)
900, 901, 902, 903, 904 comparison circuit

Claims (3)

A plurality of working systems each having a working transmission unit and a working receiving unit connected to the working line, and a spare system having a spare transmission unit and a spare receiving unit connected to the spare line, and a predetermined working system is used as the spare system. In the SDH transmission system to switch to
Set a line identification code for each active system,
When a predetermined working system is switched to the spare system, the spare transmission unit attaches a line identification code corresponding to the predetermined working system to the input signal, and passes the spare line through the spare line. Send it to the standby receiver,
In the standby receiver, the line identification code is separated from the signal received from the spare transmitter, and the received signal and the line identification code are respectively transmitted to the plurality of active receivers,
The plurality of working receiving units compare the line identification code received from the standby receiving unit with the line identification code set in the working receiving unit, and output the received signal if they match. A line switching method in an SDH transmission system. Line switching method in the SDH transmission system according to claim 1 Symbol mounting, characterized in that inserting the CIC unused bytes or undefined bytes of the section overhead. 3. A line switching method in an SDH transmission system according to claim 1, wherein when a signal indicating a line identification code of a line different from the line is transmitted, an alarm display signal is inserted into the transmitted signal. .

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