JPH0323736A - Bidirectional multidrop type transmission system - Google Patents

Abstract

PURPOSE:To perform communication normally by duplexing a multidrop type transmission line, and switching a transmission line to be used when a fault occurs in the transmission line. CONSTITUTION:The communication from a center equipment 1 to terminal equipment 2-4 are performed by using the transmission lines 5, 6, and 7, and the communication from the terminal equipments 2-4 to the center equipment 1 by using the transmission lines 10, 11, and 12 ordinarily. When information transmission from the center equipment 1 to the terminal equipment 3 is tried and no response from the terminal equipment 3 is returned via the transmission lines 11 and 12, it is judged that the fault occurs in the transmission lines 6 and 11, then, the transmission lines are switched to the transmission lines 9 and 8. Therefore, information is transmitted to the terminal equipments 3 and 4 via the transmission lines 9 and 10, and the responses from the terminal equipments 3 and 4 are transmitted to the center equipment 1 via the transmission lines 7 and 8. Also, the communication from the center equipment 1 to the terminal equipment 2 is performed by using the transmission line 5, and the response from the terminal equipment 2 to the center equipment 1 is returned by using the transmission line 12. Thereby, the information can be transmitted normally even when the fault occurs in the transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bidirectional multi-drop transmission system that can cope with failures in the transmission path by simply switching the information transmission path.

[Prior art]

Conventional information transmission systems that transmit information using wired transmission lines include a star type transmission system with the configuration shown in Figure 2, a multidrop type transmission system with the configuration shown in Figure 3, and a multidrop type transmission system with the configuration shown in Figure 4. There are a bus type transmission system and a loop type system having the configuration shown in FIG.

As shown in FIG. 2, the star type transmission system includes a center device 21 and terminal devices 22, 23 . 24 as transmission line ffi
．． ．． l. ,l. Information is transmitted from the center device 21 to each terminal device 22, 23, and 24 through transmission paths 2t*l and tffis, respectively.

Furthermore, as shown in FIG. 3, the multi-drop transmission system includes a center device 21 and terminal devices 22, 2 3 . 2
4 as the transmission line L, lt. This is an is-c series connection type, and information data transmission from the center device 21 to the terminal devices 22, 23, and 24 is performed through the transmission line lIrE+13.

Also, the bus type transmission system is as shown in Figure 4. , the center device 21 and the terminal devices 22, 23, 24 are connected via a BUS type transmission line B, and information is transmitted by specifying the address from the center device 21 to each terminal device 22, 23, 24. Transmit●Also, as shown in FIG. 5, the loop type transmission system has a center device 21 and terminal devices 22, 23, 2.
4 as transmission line 1. ．． l. ．． ! ■! 4 connected in a loop, from the center device 21 to the terminal devices 22, 23 .
Information data transmission to 24 is via transmission line 2lp lee ff
This is done through is and la.

In the information transmission system with the above configuration, if the transmission line is interrupted, the star type system only disables communication between the devices connected by the broken transmission line, and does not affect the entire system. However, in the multi-drop type, bus type, and loop type, communication becomes impossible after disconnection. In order to prevent this communication failure, as shown in Figures 6 to 8, the transmission lines are duplicated so that when one transmission line is disconnected, the transmission is switched to the other transmission line for transmission. [Problems to be Solved by the Invention] However, simply by duplicating the transmission line as described above and switching the transmission line in the event of a disconnection, it has not been possible to completely prevent communication failure.

In FIG. 6, when transmission line 2 is disconnected at point A, transmission line l. If you switch from 1 to 1 and use transmission line 1, communication failure will not occur. However, the transmission lines l8, 2, 2, and 1. and l, and 1. generally follow the same route. For,
Due to construction or other reasons, the transmission line j! , and scarcity. Both of the transmission devices 21 and 22 may be disconnected.
Communication between the communication device 23 and the transmission devices 23 and 24 becomes impossible. A similar problem exists in the bus type shown in FIG. 7 and the loop type shown in FIG.

In order to solve the above problem, in the case of a loop type transmission device, it can be solved by providing a loop pack function or a bypass function to the transmission device, but if the loop back function or bypass function is provided, communication control becomes complicated, and the information transmission system construction becomes expensive.

Furthermore, in the multi-drop type and bus type, the above problem cannot be solved by duplicating the transmission line.

The present invention has been made in view of the above-mentioned points, and by duplicating a multi-drop type transmission line and adding a simpler transmission line and transmission line switching means, it is possible to eliminate the problem when a failure occurs in the transmission line. However, the objective is to provide a bidirectional multi-drop transmission system that enables communication by switching the transmission path. [Means for Solving the Problems] In order to solve the above problems, the present invention connects a plurality of transmission devices that transmit information in series through a unidirectional transmission path, and connects the first and second devices in the transmission direction to each other. Different duplex multi-drop transmission lines are formed, and third and fourth duplex unidirectional transmission lines having different transmission directions are connected between the transmission devices located at the ends of the first and second multi-drop transmission lines. connected through sexual transmission channels,
The present invention is characterized in that one or all of the transmission devices are provided with a transmission path switching means for switching to a transmission path that allows communication depending on the situation such as a fault in the transmission path when communicating from the transmission device to a desired transmission device. [Operation] By configuring the information transmission system as described above, the form of the transmission path is the same as the conventional duplex loop type, but it is possible to simply switch to a transmission path that allows communication depending on the situation such as a failure of the transmission path. Communication is now possible, and normal communication can be performed without the need for a loop pack function or bypass function, which complicates communication control, as is the case with conventional duplex loop types.

〔Example〕

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a diagram showing the configuration of an information transmission system to which the bidirectional multi-drop transmission method according to the present invention is applied. As shown in the figure, in the information transmission system, a center device 1 and a terminal device 2 are connected by a double transmission path of a transmission path 5 and a transmission path 12, and a terminal device 2 and a terminal device 3 are connected by a transmission path 6 and a transmission path 11.
terminal device 3 and terminal device 4.
are connected by a double transmission line of transmission line 7 and transmission line 10,
Furthermore, the terminal device 4 and the center device 1 are connected to the transmission path 8 and the transmission path 9.
It is connected by a double transmission path with Here, the transmission line 5, the transmission line 6, and the transmission line 7 are each unidirectional transmission lines such as optical fiber lines, and these transmission lines form a first multidrop type transmission line. Similarly, the transmission line 10, the transmission line 11, and the transmission line 12 are each unidirectional transmission lines such as optical fiber lines, and these transmission lines form a second multidrop type transmission line. Further, the transmission line 8 and the transmission line 9 are also unidirectional transmission lines such as optical fiber lines having different transmission directions, and the transmission line 8 forms a third transmission line, and the transmission line 9 forms a fourth transmission line. form.

In the information transmission system configured as described above, if there is no fault in the transmission path, communication between the center device 1 and the terminal devices 2 to 4 is performed as follows. That is, the center device 1 and the terminal devices 2 to
4.\ communication uses transmission paths 5, 6, and 7, and terminal device 2
Communication from ~4 to the center device 1 is via the transmission line 10, it, 1.
Use 2. If a failure occurs in transmission path 6 and transmission path 11, communication from center device 1 to terminal device 2 will use transmission path 5, and response from terminal device 2 to center device 1 will use transmission path 12. . In addition, the center device 1 and the terminal device 3
, 4 uses transmission paths 9 and 10, and terminal devices 3.4 and 4 use transmission paths 9 and 10.
Communication between the center device 1 and the center device 1 is performed using transmission lines 7 and 8. That is, as described above, the center device 1 is provided with a transmission path switching means (not shown) that can appropriately switch the transmission path depending on the situation such as a fault in the transmission path.

When attempting to transmit information from the center device 1 to the terminal device 3 using the transmission paths 5 and 6, this transmission path switching means
If there is no response from the terminal device 3 through 1.12, it is determined that there is a failure in the transmission paths 6 and 11, and by switching to the transmission path 9 and 8, the transmission is transmitted to the terminal device 3 through the transmission path 9.10. Information is transmitted, and a response from the terminal device 3 is transmitted to the center device 1 via transmission lines 7 and 8.

Although the above embodiment has been mainly described with reference to the center device 1, the center device 1 and the terminal devices 2 to 4 are transmission devices that send and receive information, and if one or all of these transmission devices has a transmission path failure. It may also be possible to switch the transmission path as appropriate depending on the situation. By configuring the transmission path as described above, the transmission form is the same as the loop type, but information can be transmitted normally by simply switching the transmission path to be used in the event of a failure in the transmission path.

〔Effect of the invention〕

As explained above, according to the present invention, normal communication can be performed simply by switching the transmission path used in the event of a failure in the transmission path. This has the advantage of eliminating the need for additional functions and allowing the construction of information transmission systems at low cost. It is particularly suitable for information transmission systems where the transmission path is unidirectional, for example, using optical fiber lines.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an information transmission system according to the present invention, FIG. 2 is a block diagram showing the configuration of a star type transmission system, and FIG. 3 is a block diagram showing the configuration of a multidrop type transmission system. Figure 4 is a block diagram showing the configuration of a bus type transmission system, Figure 5 is a block diagram showing the configuration of a loop type system, and Figure 6 is a block diagram showing the configuration of a duplex multi-drop type transmission system. 7 is a block diagram showing the configuration of a duplexed bus type transmission system, and FIG. 8 is a block diagram showing the configuration of a duplexed loop type system. In the figure, 1... center device, 2, 3, 4... ...Terminal device, 5, 6, 7, 8, 9, 10, 11.12...
・Transmission line.

Claims (1)

[Claims] A plurality of transmission devices for transmitting information are connected in series through a unidirectional transmission path to form first and second double multi-drop transmission paths with mutually different transmission directions, and the first and second
The transmission devices located at the ends of the multi-drop type transmission path are connected by a third and fourth double unidirectional transmission path with different transmission directions, and one or all of the transmission devices are connected to each other from the transmission device. A bidirectional multi-drop transmission system characterized by being provided with a transmission path switching means for switching to a transmission path that allows communication depending on conditions such as a failure in the transmission path when communicating with a desired transmission device.