JP3338197B2 - Interface converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface converter for connecting a data communication device having an existing line interface to a line having a new line interface.

[0002]

2. Description of the Related Art Today, when connecting a data communication device having an existing line interface such as a telephone line modem interface to a new high-speed digital line or ISDN (Integrated Services Digital Network), the existing line interface must be connected to the new line interface. A connection method has been adopted through an interface conversion device having a function of converting the interface line into an interface line. As such an interface conversion device, there is a terminal adapter or the like. In this type of terminal adapter, a high-speed digital private line is usually used as a normal connection line with a data communication device, and a public network ISDN is used as a backup line. It is housed in a switchable manner.

[0003]

However, in a conventional interface converter such as a terminal adapter,
If communication is not performed with the partner device, it cannot be determined whether a failure has occurred, and switching to the backup line in the event of a failure will be delayed. Therefore, interface conversion that can quickly perform switching in such a case. A device was desired. In addition, since the conventional interface converter requires a function for a backup instruction on the data communication device side, the number of data communication devices that can be connected is limited, so a more versatile interface converter is required. Had been.

Further, when backup is performed, the location and cause of the failure cannot be identified during backup communication, and the resolution of the failure is delayed. Therefore, it is difficult to resolve the failure even during such backup communication. An interface conversion device that can be used has been desired.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a data communication apparatus having an existing line interface is connected to a normal connection line for performing communication through a different line interface, and the data communication device is connected to the normal connection line due to an abnormality. An interface conversion device for connecting a data communication device to a backup line for performing communication with a different line interface, which is normally connected to the connection line side and performs interface conversion between an existing line interface and a different line interface. A first conversion function unit, a second conversion function unit connected to the backup line side for performing interface conversion between an existing line interface and a different line interface, and a data communication device from the first conversion function unit A changeover switch for switching and connecting to the second conversion function unit; When an abnormality in the conversion function unit 1 is detected, an abnormality in a state where a line cannot be connected to a normal connection line, or an abnormality in a state in which communication cannot be performed with a line connected to the normal connection line, the changeover switch is activated. And a failure detection unit for transmitting a switching instruction.

Further, the interface conversion device of the present invention
In order to solve the above-mentioned problem of obtaining a device capable of solving a failure even during backup communication, an arbitrary data pattern is generated, this data pattern is transmitted to a normal connection line, and a data pattern received from a partner device. Determination unit for checking the normality of the data, and a determination result transmission unit for transmitting the determination result determined by the failure determination unit to the partner apparatus via one of a plurality of multiplexed channels on the backup line. It is characterized by having.

[0007]

In the interface conversion device of the present invention,
In normal times, the data communication device is connected to a normal connection line. In this state, the failure detecting unit detects an abnormality in the first conversion function unit, an abnormality in which the line cannot be connected to the normal connection line, or a state in which the line is connected to the normal connection line but communication is not possible. When a failure is detected, a switch instruction is sent to the switch. As a result, the changeover switch is switched, and the switch is automatically switched to the backup line.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of an interface conversion device according to the present invention. Prior to this, a basic configuration of a communication system using the interface conversion device will be described.

FIG. 2 is a general configuration diagram of the communication system. In the system shown in the figure, a data communication device 100 is connected to a terminal adapter 1, and the terminal adapter 1 as an interface conversion device accommodates a high-speed digital dedicated line 2 and an ISDN 3. The data communication device 100 includes a personal computer or the like, and has an existing line interface such as a modem interface. High-speed digital leased line (hereinafter referred to as leased line)
Reference numeral 2 denotes a new interface digital line. The ISDN 3 is used to provide backup when the high-speed digital private line 2 is interrupted.
Note that such a backup function at the time of a line failure is mounted on an advanced terminal adapter or the like as an additional function. In the figure, reference numeral 4 denotes an existing line interface, and reference numeral 5 denotes an interface for issuing a backup switching instruction (hereinafter, referred to as a switching instruction interface).

FIG. 3 is an internal configuration diagram of the terminal adapter 1. As shown, terminal adapter 1
Is a driver receiver (D / R) 6 for the existing line interface 4, a changeover switch 7, a conversion function unit (T-
a) 8, a conversion function section (T-b) 9, and driver receivers (D / R) 10 and 11.

The driver receiver 6 has a function as a driver receiver for the existing line interface, and the changeover switch 7 is connected to the backup side by an instruction given from the data communication device 100 through the switching instruction interface 5. This is a switch for enabling communication. The conversion function unit 8 has a function of performing control for converting the existing line interface 4 to the line interface of the dedicated line 2, and the conversion function unit 9 performs control for converting the existing line interface to the line interface of the ISDN 3. Has the function of performing The driver receiver 10 is a driver receiver for the dedicated line 2, and the driver receiver 11 is a driver receiver for the ISDN 3.

Next, the operation of the terminal adapter 1 having the above configuration will be described. A communication message (for example, a commonly used HDLC procedure frame) from the data communication device 100 is converted into a frame format specified in ITU recommendation I430 by the conversion function unit 8 via the driver receiver 6 and the changeover switch 7. The data is converted and transmitted to the dedicated line 2 via the driver receiver 10. Also,
In the case of reception, conversion reverse to that of transmission is performed.

Here, when communication is not possible, for example, when there is no response from the partner device, the data communication device 100 issues a switching instruction using the switching instruction interface 5, and sets the switching switch 7 to enable the ISDN 3 side. Switch. Then, after the switching, communication is performed using the ISDN 3 in the same manner as with the partner device. The conversion function units 8 and 9
Have different functions depending on the line to be connected, and generally, a dedicated LSI applied to each line is used.

Next, a description will be given of an embodiment in which the switching to the backup line can be automatically performed in the event of a failure of the dedicated line 2 without requiring a switching instruction from the data communication apparatus 100.

Embodiment 1 FIG. 1 is a configuration diagram showing Embodiment 1, and FIG. 1 shows a configuration of a terminal adapter 101 corresponding to the terminal adapter 1 of FIG.
The illustrated device includes a driver receiver (D / R) 6, a changeover switch 7, a conversion function unit (T-a) 8, and a conversion function unit (T-A).
-B) 9, driver receivers (D / R) 10 and 11, a failure detection unit 12, and a switch unit 13. Here, the driver receiver 6 to the driver receiver 11 have the same configuration as that of FIG. 3, and thus description thereof will be omitted.

The failure detecting section 12 detects whether the conversion function section 8 has an abnormality or not.
The counter 14 is provided with a function of sending a switching instruction to the changeover switch 7 when an abnormality in a state where the line cannot be connected to the dedicated line 2 or an abnormality in a state where the line is connected but communication cannot be performed is detected. It comprises a circuit 15 and a station power supply detection circuit (VD) 16.

The counter 14 has a function of validating the signal line 18 when the signal line 17 connecting the changeover switch 7 and the conversion function section 8 does not change for a certain period of time. The office power supply detection circuit 16 enables the signal line 19 when the power for office power supply supplied from the dedicated line 2 is not detected. The signal line 20 is a signal line that becomes invalid when the conversion function unit 8 establishes layer 1 level synchronization with the network of the dedicated line 2. That is, when the signal line 20 is invalid, it means that synchronization with the network has been established.
Note that this function is generally provided as an additional function of the conversion function unit 8.

The OR circuit 15 includes signal lines 18, 19, 20
And outputs the result of the logical sum operation from the signal line 21. That is, the valid signal from the counter 14, the valid signal from the station power supply detection circuit 16, the conversion function unit 8
When any one of the valid signals is input, the circuit makes the output of the signal line 21 valid. Further, the switch unit 13 is provided with a switching instruction interface 5 from the data communication device 100 or a signal line 21 from the OR circuit 15.
The switch is configured to be input to the changeover switch 7 via the signal line 22.

FIG. 4 is a block diagram for explaining the station power supply detection circuit 16. As shown in FIG. Dedicated line 2 is transmission line TA, TB
And receiving lines RA and RB, and are connected to a driver 10-3 and a receiver 10-4 via transformers 10-1 and 10-2. Generally, station power from a network is superimposed on a transmission line and a reception line, and a telephone or the like with low power consumption is operated only by the station power. With such a configuration, the station power supply is detected by comparing whether the voltage difference between the signal lines 10-5 and 10-6 from the middle point of the transformers 10-1 and 10-2 is a regular voltage. be able to.

The station power supply detection circuit 16 is connected to the signal line 10-
5, 10-6 are detected by the voltage detector 16-1, and O
If K, the signal line 16-2 becomes valid, and the signal line 19 becomes invalid via the inverting circuit 16-3. When the result of the voltage detector 16-1 is NG, the signal line 19 is similarly enabled.

FIG. 5 is a configuration diagram showing details of the counter 14. The signal line 17 between the changeover switch 7 and the conversion function unit 8 includes a transmission line (T) 17-1 and a reception line (R) 17-
2. It consists of a timing line (S) 17-3. The timing line 17-3 is always supplied from the conversion function unit 8 to the data communication device 100 at a timing synchronized with the network. The connected data communication device 100 uses the timing line 17
The transmission and reception are performed in synchronization with -3.

In the figure, reference numeral 14-1 denotes a transmitter (C
LK) and 14-2 are n-ary counters.
The signal line 14-3 from 1 is connected to the input terminal of the n-ary counter 14-2, and the timing signal from the timing line 17-3 is input to its reset terminal.

FIG. 6 is a timing chart showing the operation of such a counter 14. In such a configuration, while the timing line 17-3 is operating, the n-ary counter 1
Since the reset continues for 4-2, the n-ary counter 14-2 does not count up. However,
As shown in FIG. 6A, when the timing signal flowing through the timing line 17-3 stops due to a failure of the conversion function unit 8 or the like, the n-ary counter 14-2 counts from the point (b) in the figure. When the up is started and n + 1 is counted at the point (c) and the overflow occurs, the signal line 18 becomes valid.

As described above, in the fault detecting section 12, the abnormality of the conversion function section 8 is a valid signal output from the counter 14, and the abnormality of the state where the line cannot be connected to the dedicated line 2 is determined by the station power supply detecting circuit. The valid signal output from the circuit 16 and the abnormality in the state where the line is connected but communication is not possible are input to the OR circuit 15 by the valid signal output from the conversion function unit 8.

Next, the terminal adapter 10 having the above configuration
1 will be described. First, the operation of the normal terminal adapter 101 is the same as the operation of the terminal adapter 1 described with reference to FIGS. That is, usually, the data communication apparatus 100 is connected to the dedicated line 2 via the terminal adapter 101. In such a normal state, when the following state occurs, the failure detection unit 12 determines that a failure has occurred.

The line cable of the dedicated line 2 is cut,
Station power supply cannot be detected, and the signal line 19 from the station power supply detection circuit 16 becomes effective. Due to a network failure or the like, synchronization with the network is lost, and the signal line 20 becomes effective. The conversion function unit 8 becomes an obstacle, so that timing cannot be supplied to the existing line interface 4 side, and the signal line 18 from the counter 14 becomes effective.

When one or more of the above becomes effective, the output from the OR circuit 15 becomes effective, and this is input to the changeover switch 7 via the signal lines 21 and 22, and the changeover switch 7 is changed over. Can be As a result, the connection with the data communication device 100 is switched to ISDN3, and backup is performed. Here, the switch unit 13 is provided to select switching based on an instruction from the data communication device 100 or automatic switching by the failure detection unit 12, and this setting can be performed manually or from the data communication device 100 side. Is configured to be arbitrarily selectable, and one of them is selected by the system.

As described above, in the first embodiment, when the failure detection unit 12 detects a failure, the changeover switch 7
Since the switching to the terminal adapter 101 is performed, the data communication apparatus 100 connected to the terminal adapter 101 does not need a failure detection function, a backup instruction function for the terminal adapter 101, and the like. Irrespective of the presence or absence of backup, immediate backup support is possible. In addition, since the data communication device 100 does not require any special functions other than the existing interface, a highly versatile terminal adapter 101 can be realized.

Embodiment 2 FIG. 7 is a block diagram of Embodiment 2 of the interface conversion device of the present invention. The illustrated terminal adapter 102 (interface conversion device) includes a driver receiver (D / R) 6, a changeover switch 7, a conversion function unit (T-a) 8, a conversion function unit (T-b) 9, a driver receiver (D / R) R) 10, 11, a failure detection unit 12, a microprocessor (μP) 23, a transmission / reception controller (TRC) 24, a switch unit 25, and a loop function unit 26. Here, the driver receiver 6 to the driver receiver 11 have the same configuration as that of FIG. 3 and the first embodiment, and thus the description thereof is omitted. Further, the configuration of the failure detection unit 12 is the same as that of the first embodiment, and the illustration of the internal configuration is omitted.

The microprocessor 23 generates data for detecting a failure, controls switching of the switch unit 25, and the like, and includes a failure determination unit 23a and a determination result transmission unit 23.
The function b is realized. The failure determining unit 23a has a function of generating an arbitrary data pattern, transmitting this data pattern to the dedicated line 2, and checking the normality of the data pattern received from the partner device. Also, the determination result sending unit 23b is
It has a function of transmitting the result determined in a to one of the B channels described later in ISDN3.

The transmission / reception controller 24 performs control for converting parallel data on the microprocessor 23 side into serial data. The switch unit 25 is
The switch switches between the signal line 17 and the signal line 28 from the transmission / reception controller 24 according to an instruction on the signal line 27 from the microprocessor 23. The loop function unit 26 is a circuit that implements a loop function of returning transmission / reception data. When a loop setting is performed according to an instruction of the signal line 29 from the microprocessor 23, the transmission / reception data from the conversion function unit 8 is transmitted. The loop function unit 26 returns to the conversion function unit 8. Also, the transmission / reception data from the driver receiver 10 has a function of looping back similarly.

Further, the conversion function unit 9 for backup includes:
It is configured to accommodate two B channels in the ISDN 3 of the basic interface. One of the B channels (B1) is connected to the backup signal line 30 and the other B channel is
The channel (B2) is configured to be connected to the signal line 31 for transmitting the determination result.

Next, the operation of the second embodiment will be described. First, similarly to the first embodiment, when a failure occurs during communication on the dedicated line 2, the operation of the failure detection unit 12 causes
The changeover switch 7 is switched, and communication is performed on the backup line ISDN3. In FIG. 7, the configuration of the switch unit 13 in FIG. 1 is not shown.

At this time, since the signal line 22 is connected to the microprocessor 23, the microprocessor 23
Also recognizes the backup, and the failure determination unit 23a switches the switch unit 25 by the signal line 27, and
Is connected to the conversion function unit 8. Also, the signal line 29
The loop is set by the loop function unit 26. And
In this state, check data such as "55 (H)" and "AA (H)" is transmitted to the signal line 28 via the transmission / reception controller 24. This check data is stored in the switch unit 2
5 → Conversion function unit 8 → Loop function unit 26 → Conversion function unit 8 →
The loop is returned to the microprocessor 23 through the route of the switch unit 25 → the transmission / reception controller 24, and the failure determination unit 2
3a detects a failure inside the terminal adapter 102.

Next, the fault judging unit 23a controls the loop function unit 26 to restore the original setting (connect the conversion function unit 8 and the driver receiver 10) with the signal line 29, and performs the same operation. Send check data. As a result, the check data is transmitted to the terminal adapter 102 on the partner side via the dedicated line 2.

FIG. 8 is an explanatory diagram of the data flow in such a case. First, one terminal adapter 102
From -a, the check data is transmitted to the other terminal adapter 102-b by the above operation (shown by b in the figure). The other terminal adapter 102-b
Then, the microprocessor 23 checks the normality of the check data, and notifies the check result to the terminal adapter 102-a on one side via the ISDN 3 currently used for backup (in the figure,
c)).

Here, the basic interface ISDN3
In the case of (2), two channels (B1 channel and B2 channel) are accommodated per line, so the B1 channel is used as a backup channel (indicated by a in the figure),
Channel is free. That is, the check result is transmitted on the normally free B2 channel.

Upon receiving the check data, the terminal adapter 102-a notifies the microprocessor 23 of the determination result data from the B2 channel via the signal line 31 and the transmission / reception controller 24. Can be detected. The communication between the terminal adapter 102-a and the terminal adapter 102-b using the B2 channel is not limited to the above-described check result, but also includes a check data transmission schedule notification, a check data transmission schedule notification, and failure detection. It is used for the control or the like.

As described above, according to the second embodiment, the check data sent from the failure determination unit 23a is looped back by the loop function unit 26, and this is determined by the failure determination unit 23a. Can be determined.

Further, the check data from the failure determination unit 23a is transmitted to the other party, and the terminal adapter 1 of the other party is sent.
02, the failure determination unit 23a performs the failure determination and notifies the determination result using one of the B channels of the ISDN3. Using one channel of the line, failure detection or fault isolation of the terminal adapter 102, the network, and the line can be performed. Therefore, when a failure occurs, it is possible to take immediate measures against the failure. Further, an operator can be arranged only on one terminal adapter 102 and the status of the other terminal adapter 102 can be remotely viewed, so that a trouble countermeasure can be performed with a small number of personnel.

Third Embodiment FIG. 9 is a configuration diagram showing a terminal adapter 103 as an interface conversion device according to a third embodiment. The terminal adapter 103 shown in the figure includes a driver receiver (D / R) 6, a changeover switch 7, a conversion function unit (Ta) 8, a conversion function unit (Tb) 9, driver receivers (D / R) 10, 11. , The failure detection unit 12,
It comprises a return switch 32. Here, the configuration of the driver receiver 6 to the failure detection unit 12 is the same as that of FIG. 3 and the first and second embodiments, and thus the description thereof is omitted.

The return switch 32 has the same configuration as the switch unit 25 in the second embodiment. However, in response to a switching instruction from the failure detection unit 12, the conversion function unit 8 and the conversion function unit 9 are switched. Is different in that it is switched to connect. That is, the folding switch 3
When such switching is performed, the signal from the conversion function unit 8 is returned to the B2 channel accommodated in the conversion function unit 9.

FIG. 10 shows the terminal adapter 10 described above.
3 shows a communication system using No.3. Here, the terminal adapter 102 is a terminal adapter having the check data sending / determining function described in the second embodiment, and the terminal adapter 103 of the third embodiment is used as a partner terminal adapter. In the communication system configured as described above, in the terminal adapter 103, when the failure detection unit 12 detects a failure and issues a switching instruction to the changeover switch 7, the return switch 32
Performs switching so that data from the conversion function unit 8 is returned to the B2 channel via the conversion function unit 9.

Check data (b in the figure) from the terminal adapter 102 is sent to the ISDN via the return switch 32 and the signal line 31 in the terminal adapter 103.
From the B2 channel of No. 3 (c in the figure), the signal is looped back to the microprocessor 23, and the microprocessor 23 checks to perform fault isolation. That is, one of the terminal adapters 102 Wrapping above, and
By performing internal loopback by the loop function unit 26 described in the second embodiment, it is possible to perform fault isolation between the local side and the other side including the dedicated line 2.

FIG. 11 shows another application example of the third embodiment. In this example, the terminal adapters 102-a, 102-
b,..., 102-c, and terminal adapters 103-a, 103-
, 103-c. By adopting such a configuration, it is possible to perform loopback from the base to each region, and perform fault isolation based on the result. In FIG. 11, 100-a to 1
00-f indicates a data communication device, 2-a to 2-c indicate a dedicated line, and 3-a to 3-c indicate ISDN.

As described above, in the third embodiment, when a failure occurs, the signal from the conversion function unit 8 is turned back to the B2 channel accommodated in the conversion function unit 9 by the return switch 32. In this case, the terminal adapter 103 can omit functions such as a microprocessor, and can be realized by adding only a small number of functions to a conventional terminal adapter. Therefore, the cost can be reduced. In particular, when a plurality of terminal adapters 102 and 103 are used as shown in FIG. 11, since only half of the terminal adapters 103 need be used in the third embodiment, the effect of greatly reducing the cost of the entire system can be obtained.

FIG. 12 is an explanatory diagram of another communication system. In the figure, reference numeral 200 denotes a data communication device which directly accommodates a dedicated interface 2 or a new interface of the ISDN 3 without passing through a terminal adapter. In this data communication device, check data transmission / determination of the terminal adapters 102 and 103 described above is performed. It has a function and a loopback function. In addition, the other device is a terminal adapter 102 having a check data sending / determining function and a return function, or a terminal adapter 103 having only a return function. Even in such a communication system, the same effect as in these embodiments can be obtained by transmitting and returning check data in the same manner as in the second and third embodiments, or performing normality determination of the check data in the partner device. Can play.

In each of the above-described embodiments, the high-speed digital dedicated line is used as the normal connection line 2 and the ISDN is used as the backup line 3. However, the present invention is not limited to this. Can achieve the same effect. The backup line 3 in the second and third embodiments is not limited to the ISDN as long as a plurality of channels are multiplexed, and may be another line.

[0049]

As described above, according to the interface conversion apparatus of the present invention, the first conversion function unit is abnormal, the line connection to the normal connection line is abnormal, and the communication in the line connection state is not possible. When any one of the status abnormalities is detected, switching to the backup line is performed, so that when a failure occurs, switching can be performed quickly, and versatility can be achieved regardless of the data communication device to be connected. Interface conversion device with a high cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of an interface conversion device according to the present invention.

FIG. 2 is a general configuration diagram of a communication system.

FIG. 3 is a configuration diagram of a basic terminal adapter.

FIG. 4 is a configuration diagram for explaining a station power supply detection circuit 16 in the interface conversion device of the present invention.

FIG. 5 is an internal configuration diagram of a counter in the interface conversion device of the present invention.

FIG. 6 is a timing chart showing the operation of a counter in the interface conversion device of the present invention.

FIG. 7 is a configuration diagram of an interface conversion device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a data flow with a partner in the second embodiment.

FIG. 9 is a configuration diagram of a third embodiment in the interface conversion device of the present invention.

FIG. 10 is an explanatory diagram of a data flow with a partner in the third embodiment.

FIG. 11 is an explanatory diagram of another application example in the third embodiment.

FIG. 12 is an explanatory diagram of another communication system to which the interface conversion device according to the present invention is applied.

[Explanation of symbols]

 2 Normal connection line 3 Backup line 7 Changeover switch 8, 9 Conversion function unit 12 Failure detection unit 23a Failure determination unit 23b Determination result transmission unit 26 Loop function unit 32 Loopback switch

Claims (5)

(57) [Claims] 1. An existing line interface is set.
Data communication devices using different line interfaces
To the normal connection line for performing
The data communication device is turned on another time due to an abnormality on the connection line side.
Backup line for communication with line interface
An interface conversion device connected to the normal connection line side and connected to the existing line interface.
Interface between the interface and the different line interface.
A first conversion function unit for performing a face conversion, and an existing line interface connected to the backup line side;
Interface and the further different line interface
A second conversion function unit for performing an interface conversion of the data communication device;
Switch for switching connection to the conversion function unit 2
And pitch, either said first conversion function abnormalities, the normal state can not line connection to the connection line abnormalities and the normal state can not communicate in a state of being line connection to the connection line abnormality detection result, the interface conversion device characterized by comprising a failure detection unit for sending a switching instruction to the changeover switch or. 2. The interface conversion device according to claim 1, wherein the first conversion function unit sends a valid signal when network synchronization with the normal connection line is lost, and copes with the network synchronization. Output the timing signal to the data communication device side, the valid signal of the first conversion function unit, the valid signal output when the station power supply signal from the normal connection line is not detected, and the timing signal An interface conversion device, further comprising an abnormality detection unit that determines that an abnormality has occurred when any one of the valid signals output in the case where the valid signal is not output. 3. A interface converter according to claim 1 or 2, wherein, to generate arbitrary data pattern, sends out the data pattern to the normal connection line via the first conversion function, the normal A failure determination unit that checks the normality of a data pattern received from the connection line; and a failure determination unit that is provided between the first conversion function unit and the normal connection line and that receives an instruction from the failure determination unit. An interface conversion device comprising: a loop function unit that loops back a data pattern sent from the control unit to the failure determination unit. 4. The interface converter according to claim 1, wherein a backup line having a plurality of multiplexed channels is provided.
A determination, to generate arbitrary data pattern, sends out the data pattern to the normal connection line, and a fault determining unit that checks the normality of the data pattern received from the other unit, it is judged by the failure judgment unit An interface conversion device comprising: a determination result transmission unit that transmits a result to the partner device via one channel of the backup line. 5. The interface converter of claim 1, wherein the backup line Bei a plurality of channels multiplexed
For example, based on the switching instruction output from the fault detection unit,
Interface conversion device is characterized by providing a turn-back switch for folding the data sent through the normal connection line through one of the channel in the backup line.