JP2000278295A - Information transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an information transmitter that can transmit information normally by detecting a broken line and selecting a normal line if one transmission line is broken in a bus type transmission line. SOLUTION: A loop type transmission line 28 interconnects a master station 1 and a plurality of slave stations 24-27. The information transmitter 1 is provided with line changeover relay contacts 11, 12 to configure two clockwise and counter clockwise circuits in the transmission line, a controller 2 that is arranged on the side of the master station 1 and controls the contacts 11, 12 so as to bring, e.g. the contact 11 into an open state and the contact 12 into a closed state, and a slave station position storage section that is arranged in the master station and stores slave station position. The broken position is located on the basis of the slave station position stored in the storage section and a block line state detected by a fault detection section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information transmission apparatus for transmitting information between a specific transmission station (master station) of a plurality of transmission stations and another transmission station (slave station).

[0002]

2. Description of the Related Art Conventionally, as an example of an information transmission apparatus, FIG.
As shown in FIG. 3, a master station 1 which is a specific transmission station among a plurality of transmission stations, and slave stations 24, 25, 26 and 2 which are other transmission stations.
7 are electrically connected by a bus-type transmission line 28, and information is mutually transmitted between the master station 1 and the slave stations 24-27.

[0003] The master station 1 includes a control device 2 for controlling communication.
And a transceiver (transmitter / receiver) 3. Slave station 2
4 includes a control device 18 and a transceiver (transmitter / receiver) 19 similarly to the master station 1, and the other slave stations 25 to 27 also include a control device 18 and a transceiver (transmitter / receiver) 19 similarly.

[0004] Terminators (termination resistors T1 and T2) 15A and 16A are arranged at the ends of the bus-type transmission path 28, respectively. Here, the terminator is for preventing a waveform distortion due to reflection occurring in the cable by connecting a resistor having a characteristic impedance equal to the characteristic impedance of the communication electric cable to an end of the cable. Specifically, when the end of the cable is opened, the signal travels as a wave in the cable, reflects at the end of the cable, and the original waveform and the reflected wave overlap with a time lag, resulting in waveform distortion. Occurs. Further, when cables having different characteristic impedances are connected, a part of the signal is reflected at the connection part and the remaining part is transmitted, so that waveform distortion occurs. In order to prevent this waveform distortion, a resistor having a predetermined impedance connected to the end of the cable is called a terminator.

[0005] An information transmission device having such a configuration is
For example, in order to apply to railway vehicles, the master station 1 is arranged in the first car, and the slave stations 24 to 27 are sequentially arranged in subsequent cars, and a bus type is arranged between the master station 1 and the slave stations 24 to 27. Transmission line 28
A is arranged and connected.

In the case of such a bus type transmission line 28A, if a certain point on the transmission line is broken, the master station 1 and the slave station 2
Since there is a slave station in which communication cannot be performed in 4 to 27, a normal operation cannot be performed due to disconnection at one place.

[0007]

Normally, when a transmission system is constructed, a system having redundancy so as to continue operation without any trouble even if a single line disconnection or the like occurs in consideration of a disconnection of a transmission line or the like. desired. The loop transmission path is one transmission path configuration having such redundancy. However, in the case of the bus-type transmission path 28A, the transmission system does not operate normally due to disconnection at one location.

According to the present invention, when a transmission line is disconnected at one place,
An object of the present invention is to provide an information transmission device capable of normal information transmission by detecting a disconnection and switching a line.

[0009]

In order to achieve the above object, an invention according to claim 1 provides a loop type transmission between a transmission station constituting a master station and a plurality of transmission stations constituting a plurality of slave stations. An information transmission apparatus connected by a transmission path, wherein the loop transmission path is forcibly switched to a bus transmission path.

In order to achieve the above object, the invention according to claim 2 connects a transmission station constituting a master station and a plurality of transmission stations constituting a plurality of slave stations by a loop-type transmission line, A switching device having first and second opening / closing means for forming two circuits, clockwise and counterclockwise, on the transmission line; and a switching device arranged on the master station side for controlling the opening / closing means. The first opening / closing means is in an open state, and the second opening / closing means is
And a control device for closing the opening / closing means of the information transmission device, wherein the loop-type transmission line is forcibly switched to a bus-type transmission line.

According to a third aspect of the present invention, the communication between the master station and the slave station is controlled by controlling the operations of the first and second opening / closing means to be opposite to each other. Confirm that there is a response from the slave station that detected the communication error,
And if there is no response from the responding slave station,
When the transmission path is determined to be disconnected, and when the communication state does not change by switching the first and second opening / closing means, the apparatus further includes abnormality detection means for determining that the slave station has failed. If the abnormality detection means detects a disconnection in the transmission line,
3. The information transmission device according to claim 2, wherein the transmission path can be configured as a bus again by closing both the first and second opening / closing means.

To achieve the above object, the invention according to claim 4 further comprises a slave station position storage means arranged in the master station for storing a connection position of the slave station on a transmission line, wherein the abnormality detection is performed. Means for detecting the disconnection point of said transmission path based on the presence or absence of a response from a slave station when disconnection of said transmission path is detected by means and a slave station position stored in said slave station position storage means. 2 is an information transmission device.

In order to achieve the above object, an invention according to claim 5 is an invention according to a fifth aspect, wherein each of the slave stations is connected to a connection point of the transmission line to form two clockwise and counterclockwise circuits. Controlling the first and second opening / closing means and the opening / closing means on the slave station side to detect the position of the slave station connected to the transmission line, and controlling the slave stations to be connected one by one; And a switching unit control unit that stores the position where the slave station is connected by the switching unit control unit and the switching unit in the slave station position storage unit. An information transmission device according to any one of the above.

In order to achieve the above object, the invention according to claim 6 is characterized in that a connection point between the transceiver provided in the master station and the transmission line and a connection point between the transceiver provided in each slave station and the transmission line are respectively provided. Connected, a terminator for notifying the end of the network, connected between each of the terminators and the transmission line, and connected to each of the terminators, a terminator opening and closing means for disconnecting, and a terminator for the terminator opening and closing means. When the disconnection of the transmission line is detected, the line is switched, and when the bus-type transmission line is configured again,
6. The information transmission apparatus according to claim 2, further comprising: a terminator control unit that issues a terminator connection command to slave stations on both sides of the disconnection point.

In order to achieve the above object, the invention according to claim 7 is such that the slave station position storage means stores the position of the slave station connected to the transmission line as data in advance by the master station. The information transmission apparatus according to claim 4, wherein the terminator connection control is performed on a normal transmission line by configuring and recognizing a terminal station at the end and transmitting a connection command of the terminator.

In order to achieve the above object, an invention according to claim 8 is for automatically recognizing the position of a slave station connected to the transmission line, wherein each of the slave stations is turned on when the power is turned on. An opening / closing means control device for turning on the first and second opening / closing means of the station one by one;
7. The information transmission apparatus according to claim 6, wherein by transmitting a terminator connection command to the slave station, terminator connection control on a normal transmission path can be performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to FIGS. 8 is different from the conventional example of FIG. 8 in that a bus-type transmission path 28A having terminators 15A and 16A is not provided, and instead a loop-type (ring-type) transmission path 28 is prepared, and this is used as a loop-type (ring-type)
The transmission line 28 is connected to the transceiver 3 of the master station 1 and each of the slave stations 24 to
It is connected between 27 transceivers 19.

The master station 1 is provided with switching means, for example, switching relay contacts 11, 12 and a switching device 4 comprising a terminator (T1) 15 and terminator switching means, for example, a terminator connection relay contact 13. The terminator 1 is connected to the connection point via the contact 13
5 are connected, and contacts 11 and 12 are connected to a connection point between the transceiver 3 and the transmission line 28.

Further, the slave stations 24 to 27,
Circuit switching opening / closing means, for example, a line switching relay contact 2 between connection points of each of the transceivers 4 to 27 and the transmission line 28;
0 and 21 are connected respectively. In this case, each contact 20,
21 is in series with the transmission line 28 and each transceiver 19
, One of the contacts 20 and 21 is connected in series.

A terminator 22 is connected between an input of each transceiver 19 of each of the slave stations 24 to 27 and a connection point between the contacts 20 and 21 with a terminator connection relay contact 23 inserted in series. .

Further, the control unit 2 of the master station 1 includes a switching control unit 5, an abnormality detection unit 6, a terminator control unit 7, a slave station line relay control unit 8, a slave station position storage unit 9, a communication control unit 10.
Is provided.

The switching control unit 5 includes a line switching relay contact 1
In order to turn on one of the switches 1 and 12, for example, 11 and turn off the other, for example 12, or to reverse them, two sets of line switching relays (not shown) installed in the control device 2 are provided. To control.

The abnormality detecting section 6 detects that communication between the master station 1 and the slave stations 24 to 27 cannot be performed due to disconnection or the like. The terminator control unit 7 includes the terminator 1
In order to turn on and off the terminator connection relay contacts 13 and 23 connected to the input sides of the terminals 5 and 22, for example, a terminator connection relay (not shown) installed in the control device 2 is controlled.

The slave station line relay control section 8 controls a slave station line switching relay (not shown) installed in the control device 2, for example, to turn on and off the line switching relay contacts 20 and 21. Is what you do.

The slave station position storage unit 9 stores the slave stations 24 to 27 on the transmission line 28. The communication control unit 10
It controls the timing of communication between the master station 1 and the slave stations 24-27.

With such a configuration, an embodiment corresponding to each claim will be described. According to an embodiment corresponding to claims 1 and 2, when the transmission line 28 is disconnected, the switching control unit 5 in the control device 2 of the master station 1
By controlling only the relay contact 12 of the set of line switching relay contacts 11 and 12 to be turned on, the loop transmission line 28 is forcibly changed to a bus transmission line as shown in FIG. As a result, normal information transmission becomes possible even if the transmission line 28 is disconnected.

In the embodiment corresponding to claim 3, communication control is normally performed by the communication control unit 10 in the control device 2 in the master station 1, and communication with certain slave stations 24 to 27 due to disconnection or the like. Detect that it is no longer possible. Upon detecting the communication abnormality, the abnormality detecting unit 6 requests the switching control unit 5 to turn on and off the contacts 11 and 12 of the line switching relays, and sets two sets of line switching. Control the relay. In this state, communication control is performed so that communication can be performed with the slave station in which communication has failed, and communication with the slave station in which communication has been disabled cannot be performed. Is determined, and a control instruction signal is output from the control device 2 so as to turn on both the contacts 11 and 12 of the line switching relay, thereby forming a bus-type transmission path again.
If the communication state does not change even after switching the line switching relay contacts 11 and 12, it is determined that the slave station is abnormal, and the line switching relay contacts 11 and 12 in the switching device 4 are returned to the original state. Control to return.

An embodiment corresponding to claim 4 is claim 2.
When disconnection detection is performed in the embodiment corresponding to
The disconnection point is specified by the abnormality detection unit 6 from the position of the child station previously stored in the child station position storage unit 9 in the control device 2 of the master station 1 and the communication state when the disconnection is detected.

An embodiment corresponding to claim 5 is the master station 1,
When the power of the slave stations 24 to 27 is turned on, the switching device 4 in the master station 1
In a state where only the line switching relay contact 12 is turned on and the transmission path is of a bus type, the line switching relay contacts 20 of the slave stations 24 to 27 other than the master station 1 are connected to all the slave stations 24 to 27. An instruction to turn off is transmitted from the control device 2, and in this state, a response from the slave station is waited, and it is determined that the slave station that has responded is first connected to the master station.

To determine the next connected slave station, the master station 1 sends a message to the slave stations 24-27 that have confirmed the connection.
An instruction to turn on the off line switching relay contact 20 is transmitted and a response is waited, and it is determined that a slave station having a new response is connected next. Similarly, the relays are sequentially turned on one by one, and a slave station having a new response is recognized, and a connection order is recognized. In addition, even when the relay is turned on, the connection state of the slave station is automatically determined by determining that the response state remains the last time as the terminal slave station, and the position data is stored in the slave station position storage unit. 9 and when disconnection is detected,
The disconnection point is detected from the response from the slave station when the disconnection is detected and the position of the slave station automatically determined.

An embodiment corresponding to claim 5 is the invention according to claims 3 and 4, wherein a disconnection point is detected and the master station 1 is detected.
Then, both of the line switching relay contacts 11 and 12 in the switching device 4 are turned on to form a bus-type transmission path again.

Thereafter, in order to connect a terminator to the terminal portion of the transmission line at the disconnected point,
A terminator connection command is transmitted from the control device 2 of the master station 1. The two terminal stations at the end receive the command and control to connect the terminator. In this case, the control device controls the terminator in the master station 1 to be turned off.

An embodiment corresponding to claim 6 is claim 2.
In the embodiment according to any one of claims to 5, when performing terminator connection control on a normal transmission line (a transmission line that is not disconnected), the slave station position storage unit 9 in the control device 2 of the master station 1 By storing the connection position of the slave station on the transmission line as data in advance, it recognizes which slave station is the terminal slave station, transmits a terminator connection command to the slave station when the power is turned on, and connects the terminator. Relay contact 2
3 are connected. The other terminator controls terminator connection on a normal transmission line by turning on a terminator connection relay contact 13 for connecting the terminator 15 in the master station 1.

An embodiment corresponding to claim 7 is claim 4.
In the described embodiment, when terminator connection control is performed on a normal transmission line (a transmission line that has not been disconnected), by automatically recognizing the connection order of slave stations when the power is turned on,
The terminal station automatically determines the terminal station, transmits a terminator connection command to the terminal station, and connects the contact 23 of the terminator connection relay. The other terminator turns on a terminator connection relay contact 13 for connecting the terminator 15 in the master station 1,
The terminator connection control in the normal transmission path is performed.

The operation and effect of the above-described embodiment of the present invention will be described with reference to FIGS.

FIG. 4 shows a configuration of the transmission line 28 in a state where the power can be turned on and a normal operation can be performed. FIG. 5 illustrates an operation flow from the power-on state to a configuration of the normal transmission line 28. It is a flowchart for performing. When the power of the master station 1 and the slave stations 24 to 27 shown in FIG. 4 is turned on, the control device 2 of the master station 1 operates the line switching relay contact 1 in the switching device 4.
Of the contacts 1 and 12, the contact 11 is controlled to be off and the contact 12 is turned on (S1), and the wiring of the loop transmission line 28 is forcibly used as a bus transmission line.

Each of the slave stations 24 to 27 turns on the line switching relay contacts 20 and 21, and the terminator 22.
Is controlled by the control devices 18 of the slave stations 24 to 27 to turn off the terminator connection relay contact 23 so as not to connect (S2).

Since the transmission path 28 is configured in this manner, the connection of the terminators 15 and 22 is controlled next. Specifically, in the master station 1, the terminator 15 is connected by turning on the terminator connection relay contact 13 by the control device 2, and the terminator connection relay contact 23 in the slave stations 24 to 27 is connected to the slave station 24 to 27. The terminator 22 is connected by turning it on by the control device 18.

In this state, in order to recognize the positions of the terminal stations 24 to 27 at the end, the control device 2 of the master station 1
7 so as to turn off all the one line switching relay contacts 20 to all the slave stations 24-27. Then
Each of the slave stations 24 to 27 receives the transmission command, and
The control device 18 turns off the line switching relay contact 20 (S3).

In steps S4 to S7 described below, the line switching relays 20 and 21 in the slave stations 24 to 27 are turned on one by one to recognize the connection order of the slave stations 24 to 27. That is, the control device 2 of the master station 1 waits for a communication response from the slave stations 24 to 27, and determines that the slave station that has returned the response is connected first. In FIG. 4, the slave station 27 and the numbers of the slave stations are stored in the slave station position recognition area in the slave station position storage unit 9 so that the connection order can be recognized.

Next, the control device 2 transmits to the slave station that has returned a response so as to turn on the line switching relay contact 20 that has been turned off. The slave station receives the order,
The line switching relay contact 20 is turned on. Further, the mobile station waits for a response from the mobile station in this state, and determines that the mobile station to which a new response has been returned is connected next (mobile station 26 in FIG. 4). Similarly, by turning on the line switching relay contacts 20 of the slave station 25 that has newly responded one by one, the connection order is recognized, and the slave station position recognition area in the slave station position storage unit 9 is recognized. It is stored (S5, S6, S7).

In S4, if there is no new response from the slave station, it is determined that the new station is the terminal station (here, 24).

After recognizing the connection order of the slave stations as described above, a connection command is transmitted from the control device 2 to the terminator connection relay contact 23 to the terminal slave station [slave station 24 in FIG. By turning on 23, the terminator 22
Connect.

As described above, the configuration of the bus-type transmission line and the terminator connection control for connecting the terminator 22 are forcibly performed from the loop-type transmission line 28, and the configuration operation of the bus-type transmission line is completed.

As described above, the connection positions of the slave stations 24 to 27 are recognized, and this is stored in the slave station position storage unit 9.
The operation when the transmission line 28 is disconnected in a state where information transmission is normally performed between the master station 1 and the slave stations 24 to 27 will be described with reference to FIGS.

FIG. 6 shows a configuration in the case where a disconnection occurs in the transmission line 28, and FIG. 7 shows a flowchart in a case where the line is switched after the disconnection has occurred and the bus-type transmission line is reconfigured. .

In FIG. 6, it is assumed that a disconnection occurs between the slave station 25 and the slave station 26 at the position indicated by X in the figure (29 in FIG. 6). In this case, the slave station 2
Communication response from 4 and 25 is lost, and communication error
Is detected by the abnormality detection unit 6 of the control device 2 (S11).

The control device 2 that has detected the communication abnormality determines that the connection is broken, and turns on the line switching relay contact 11 and the line switching relay contact 12 in the switching device 4 (S12).

In this state, it is determined whether there is a communication response from the slave stations 24 and 25 by switching the line (S13). When there is a response from the slave stations 24 and 25 that have detected the communication abnormality, and there is no response from the slave stations 26 and 27 that have responded, the slave station 2
It is determined that there is a disconnection between 5 and 26.

If it is determined that the transmission line 28 is broken, it is necessary to control the connection of the terminator. This is for recognizing a disconnection point from data in which the position of the slave station is set in advance from slave station position data stored in the slave station position storage unit 9 and data in which a communication error has occurred. In this example, it is determined that there is a disconnection in the transmission path 28 between the slave stations 25 and 26 in FIG. 6 (S14).

After recognizing the disconnection point, in order to control the connection of the terminator 22 to the slave stations 25 and 26, the connection instruction of the terminator 22 to the slave stations 25 and 26 at both ends of the disconnection point, that is, the terminator connection relay An instruction is given to the contact 23. In FIG. 6, a terminator connection instruction is issued between the slave stations 25 and 26 (S15). The slave stations 25 and 26 that have received the terminator connection instruction turn on the terminator connection relay contact 20 to connect the terminator 22.

Then, the terminator connected so far is controlled to be turned off. Specifically, the terminator connection relay contact 14 and the terminator connection relay contact 2
3 is turned off, and the terminator connection relay contact 13 in the master station 1 is turned off (S16).

In S13, when there is no response from the slave stations 24 and 25, even if the line switching relay contacts 11 and 12 are switched back to the original state [contact 11 is off, contact 12 is on], the communication state is changed. If not, it is determined that the slave stations 25 and 26 are out of order (S17, S18).

As described above, when the transmission line 28 is disconnected, the loop type transmission line 28 is reconfigured into a bus type transmission line.

According to the above-described embodiment, the loop-type transmission line 28 is forcibly used as a bus-type transmission line, so that even if one transmission line is disconnected, the line is switched to be used again. Since a bus-type transmission path can be configured, normal information transmission becomes possible.

Also, terminators 15 and 22 are provided in the master station 1 and the slave stations 24 to 27, and a relay is provided so that the connection of the terminators 15 and 22 can be turned on and off. In addition, since the terminator connection control can be performed when the disconnection is detected, normal operation can be continued even when the transmission line is disconnected.

<Modification> In the above-described embodiment, the terminator (T2) is connected via the terminator connection relay contact 14 to the connection point between the line switching relay contact in the switching device 4 and the transmission line 28 in the master station 1. ) 16 is not connected, but as shown in FIG. 1, the terminator connection relay contact 14 and the terminator 16 may be additionally connected. With this configuration,
When terminator connection control is performed on a normal transmission line (a transmission line that has not been disconnected), when the power is turned on, the terminator 22 of the slave station is transmitted from the control device 2 of the master station 1 so as to be turned off, By connecting only two of the terminators 15 and 16, terminator connection control on a normal transmission path can be performed regardless of the positions of the slave stations 24 to 27.

The line switching relay contact 1 described above
1, 12, 20, 21 and the terminator connection relay contacts 13, 14, 23 are not limited to this, and any other circuit opening / closing means may be used.

Further, in the master station 1, the slave station position storage section 9 provided in the installed control device 2 stores the master station 1 and the slave stations 24 to 27 after turning on the power.
Confirms the position connected to the transmission line 28 and stores it. Alternatively, if the positions where the slave stations 24 to 27 are connected to the transmission line 28 are known in advance, the It can also be stored in the position storage unit 9.

[0060]

According to the present invention described above, the number of transmission paths is one.
When a disconnection occurs at a certain point, an information transmission apparatus capable of normal information transmission can be provided by detecting the disconnection and switching the line.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an information transmission device of the present invention.

FIG. 2 is a configuration diagram of a master station (transmission station) in FIG. 1;

FIG. 3 is a configuration diagram of a slave station (transmission station) in FIG. 1;

FIG. 4 is a configuration diagram for explaining an operation from power-on to connection of a terminator in the embodiment of FIG. 1;

FIG. 5 is a flowchart illustrating an operation from power-on to terminator connection in the embodiment of FIG. 1;

FIG. 6 is a configuration diagram for explaining operations from transmission line disconnection to bus-type transmission line reconfiguration in the embodiment of FIG. 1;

FIG. 7 is a flowchart for explaining operations from transmission line disconnection to bus type transmission line reconfiguration in the embodiment of FIG. 1;

FIG. 8 is a schematic configuration diagram showing an example of an information control device having a conventional bus-type transmission line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmission station (master station) 2 ... Control device (master station) 3 ... Transceiver (master station) 4 ... Switching device (master station) 5 ... Switching control part 6 ... Abnormality detection part 7 ... Terminator control part 8 ... slave station Line relay control unit 9 ... Slave station position storage unit 10 ... Communication control unit 11 ... Line switching relay contacts 12 ... Line switching relay contacts 13 ... Terminator connection relay contacts 14 ... Terminator connection relay contacts 15 ... Terminator 16 ... Terminator 17 ... Transmission station (slave station) 18 ... Control device (slave station) 19 ... Transceiver (slave station) 20 ... Line switching relay contact 21 ... Line switching relay contact 22 ... Terminator 23 ... Terminator connection relay contact 24 ... Transmission Station (slave station) 25 ... Transmission station (slave station) 26 ... Transmission station (slave station) 27 ... Transmission station (slave station) 28 ... Transmission path 29 ... Disconnection position

Continued on the front page (72) Inventor Masahiro Yaginuma 2-2-2, Yoyogi, Shibuya-ku, Tokyo East Japan Railway Company (72) Inventor Satoshi Toba 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Fuchu Plant F term (reference) 5K031 AA08 DA02 EC01 5K032 AA06 DA01 DB03 DB12 DB19 EC01

Claims (8)

[Claims] 1. A transmission station constituting a master station and a plurality of transmission stations constituting a plurality of slave stations are connected by a loop transmission line, and the loop transmission line is forcibly changed to a bus transmission line. An information transmission device configured to be switchable. 2. A transmission station constituting a master station and a plurality of transmission stations constituting a plurality of slave stations are connected by a loop transmission line, and two circuits, clockwise and counterclockwise, are connected to the transmission line. A switching device having first and second opening / closing means for configuring; and a switching device arranged on the master station side for controlling each of the opening / closing means, wherein the first opening / closing means is in an open state. A control device for closing the second opening / closing means; and a control device for forcibly switching the loop-type transmission line to a bus-type transmission line. 3. Controlling the operations of the first and second opening / closing means to be opposite to each other, confirming the communication state between the master station and the slave station, and receiving a response from the slave station detecting the communication abnormality. If there is no response from the slave station that has responded, it is determined that the transmission path is disconnected, and the first and second opening / closing means are switched to change the communication state. In such a case, the apparatus further comprises abnormality detecting means for judging that the slave station has failed. When the abnormality detecting means detects a disconnection of the transmission line, both of the first and second opening / closing means are closed. 3. The information transmission apparatus according to claim 2, wherein said transmission path can be configured again as a bus type. 4. A slave station which is disposed in the master station and stores a connection position of the slave station on a transmission line, wherein the slave station detects a disconnection of the transmission line by the abnormality detecting means. 3. The information transmission apparatus according to claim 2, wherein the disconnection point of the transmission path can be detected based on the presence or absence of a response from the slave station and the slave station position stored in the slave station position storage means. 5. First and second opening / closing means respectively connected to a connection point between each of the slave stations and the transmission line to form two clockwise and counterclockwise circuits, and connected to the transmission line. An opening / closing means control device for controlling the opening / closing means on the slave station side so as to detect the position of the slave station, and controlling the slave stations to be connected one by one. The information transmission apparatus according to any one of claims 2 to 4, wherein a position at which the slave station is connected by the control device and the opening / closing means is stored in the slave station position storage means. 6. A terminator connected to a connection point between the transceiver included in the master station and the transmission line, a connection point between the transceiver included in each slave station and the transmission line, and for notifying the end of the network, A terminator opening / closing means connected between each of the terminators and the transmission line, for connecting and disconnecting each of the terminators, and when the disconnection of the transmission line is detected with respect to the terminator opening / closing means, the line is switched, and again. 6. The information transmission apparatus according to claim 2, further comprising: a terminator control unit configured to issue a terminator connection command to slave stations on both sides of the disconnection point when a bus-type transmission path is configured. . 7. The slave station position storage means is configured such that the master station stores the position of the slave station connected to the transmission line as data in advance, recognizes the slave station at the end, and stores the position of the terminator. 5. The information transmission apparatus according to claim 4, wherein the transmission of the connection command enables the terminator connection control on a normal transmission path. 8. The position of a slave station connected to the transmission line,
For automatically recognizing, further comprising an opening / closing means control device for turning on the first and second opening / closing means of each of the slave stations one by one when the power is turned on, and determining a terminal slave station; 7. The information transmission apparatus according to claim 6, wherein a terminator connection control on a normal transmission path can be performed by transmitting a terminator connection command to the slave station.