JP2002344642A - Remote supervisory system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a master station unit acting like an execution system continues its operation in spite of occurrence of a fault therein because of discrimination of itself as the execution system, and when other system becomes the execution system a master station unit acting newly like the execution system cannot be correctly connected to an external communication line. SOLUTION: When both the master station units in duplicate output a line connection request signal to a line changeover device, the line changeover device connects the master station unit outputting later the line connection request signal to an external communication line. Furthermore, the master station unit receives the line connection signal from the line changeover device to confirm the connection of the master station unit to the external line and then conducts communication.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system in a remote monitoring system for automatically connecting an execution system of a master station device duplexed to one host device to an external communication line.

[0002]

2. Description of the Related Art A communication method for connecting an execution system of a duplicated master station device to an external communication line in a conventional remote monitoring system will be described with reference to the block diagram of FIG.

When the master station device 2A is in the active system and the master station device 2B is in the standby system, the master station device 2A sends a line switching signal 13A and a status signal 17A indicating that the own device is the active system to the line switching device 3. Output. The line switching device 3 includes a monitoring circuit 8
At A, a status signal 17A is taken in, a status signal 18A indicating that the master station device 2A is an active system is output, and a line switching signal 13A and a status signal 18A are taken in by an AND circuit 9A. Switching signal 19A
Is output, whereby the line switch 10 connects the external communication line 16 to the communication line 12A.

[0004]

In the above prior art, line switching is performed when an AND condition between the line switching signal output from the master station device and the monitoring result of the status signal indicating the active system is satisfied. I was Therefore, in spite of the occurrence of a failure in the master station device of the active system, if the own device is determined to be the active system and continues to operate, and the other system becomes the active system,
There was a case where the newly executed master station device could not be properly connected to the external communication line.

Further, when communication is interrupted, it has not been possible to specify which of the master station device, the line switching device, the external communication and the like has the cause.

An object of the present invention is to solve the above problems.

[0007]

In order to achieve the above object, when a line connection request signal is output from both of the duplexed master station devices to the line switching device, the line switching device outputs the line connection request signal later. The master station device is connected to an external communication line. Further, the master station device receives the line connection signal from the line switching device, confirms that the own device is connected to the external line, and then performs communication.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention.

When the host device 1 communicates with the master device 2A as the active system, the master device 2A receives communication from the host device 1 and, when communication with the slave station is possible, a line connection request signal. 13A is output to the line switching device 3. In the line switching device 3, the line connection request signal 13A output from the master station device 2A is input to the last-in priority circuit 4, and the last-in-priority circuit 4 outputs the line switching signal 15 to the changeover switches 5 and 6.
The communication line 12A is connected to the external communication line 16 by the changeover switch 6, and the line connection signal 14A output from the line connection signal source 7 is output to the master station device 2A by the changeover switch 5. The master station device 2A takes in the line connection signal 14A output from the line switching device 3 and performs communication with the slave station. When the host device 1 communicates with the master station device 2B as an active system, the master device 2B
Receives the communication from the host device 1 and outputs a line connection request signal 13B to the line switching device 3 when communication with the slave station is possible. In the line switching device 3, the line connection request signal 13B output from the master station device 2B is input to the last-in-time priority circuit 4, and the last-in-time priority circuit 4 causes the line switching signal 15 to be output.
Are output to the changeover switches 5 and 6, the communication line 12B is connected to the external communication line 16 by the changeover switch 6, and the line connection signal 14B output from the line connection signal source 7 by the changeover switch 5 is transmitted to the master station device 2B. Is output to The master station device 2B takes in the line connection signal 14B output from the line switching device 3 and performs communication with the slave station.

When a failure occurs in the master station device 2A, the host device 1 switches to perform communication using the master station device 2B as an active system. The master station device 2B receives the communication from the higher-level device 1 and outputs a line connection request signal 13B to the line switching device 3 when communication with the slave station becomes possible. In the line switching device 3, a line connection request signal 13B output from the master station device 2B is input to the last-in priority circuit 4, and the last-in priority circuit 4 outputs a line switching signal 15 to the changeover switches 5 and 6, and 6 and communication line 12B
Is connected to the external communication line 16, and the line connection signal 14B output from the line connection signal source 7 by the changeover switch 5 is output to the master station device 2B. Master station device 2B
Captures the line connection signal 14B output from the line switching device 3 and performs communication with the slave station.

In the above line switching, the master station device 2A becomes a standby system because there is no communication from the host device 1, and the line connection request signal 13A is not output.
Even if an operation similar to that of the execution system is performed for some reason and the line connection request signal 13A continues to be output, the line connection request signal output from the master station device 2B output later by the last-in priority circuit 4 13B is given priority, and the line can be correctly switched.

Here, the operation of the last-insertion priority circuit 4 in the present embodiment will be described. FIG. 2 shows the configuration of the last-in-first-out circuit. In the present embodiment, the master stations 2A and 2B output a pulse signal having a period T as a line connection request signal, and the switch 6 connects the communication line 12A to the external communication line 16 when the line switching signal 15 is at a high level. When the level is low, the communication line 12B is connected to the external communication line 16, and the changeover switch 5 causes the line connection signal 14A to be output to the master station device 2A when the line switching signal 15 is high, and when the level is low. It is assumed that the line switching signal 14B is output to the master station device 2B. In FIG. 2, when the input signal rises from a low level to a high level, the one-shot pulse generation circuits 21A and 21B have a width T1 (T1
> T), and the one-shot pulse generation circuits 22A and 22B output one low-level pulse when the input signal rises from a low level to a high level.

FIG. 3 shows a time chart when the host device 1 performs communication with the master station device 2A as the active system and then switches to perform communication with the master station device 2B as the active system. When the master station device 1 is the active system, the line connection request signal 13
The pulse signal is a one-shot pulse generation circuit 21 as A
A, and the line connection request signal 23A becomes high level. With the rise of the line connection request signal 23A,
The line switching signal 25A goes high, one low-level pulse is output to the clear signal 24A by the one-shot pulse generation circuit 22A, and the line switching signal 25B goes high. The AND circuit 26 outputs the line switching signal 25
A and 25B are taken in, and the line switching signal 15 is set to a high level. Next, when the master station apparatus 2B is switched to the active system, a pulse signal is input to the one-shot pulse generation circuit 21B as the line connection request signal 13B, and the line connection request signal 23B becomes high level. When the line connection request signal 23B rises, the line switching signal 25B goes low, and the one-shot pulse generation circuit 22
B outputs one low-level pulse to the clear signal 24B, and the line switching signal 25A goes low. AN
The D circuit 26 takes in the line switching signals 25A and 25B and sets the line switching signal 15 to low level.

FIG. 4 shows a time chart when the master station device 2A performs the same operation as the execution system for some reason in the above line switching and continues to output a pulse signal as the line connection request signal 13A. . At this time, the line connection request signal 23 is output by the one-shot pulse generation circuit 21A.
A continues to be at the high level, but the pulse signal output later as the line connection request signal 13B by the master station device 2B is input to the one-shot pulse circuit 21B, and the line connection request signal 23B becomes the high level, and the line connection When the request signal 23B rises, the line switching signal 25B goes low, and the one-shot pulse circuit 22B
As a result, one low level pulse is output to the clear signal 24B, and the line switching signal 25A becomes low level. AND
The circuit 26 takes in the line switching signals 25A and 25B and sets the line switching signal 15 to low level.

If the communication with the slave station is interrupted during communication with the master station apparatus 2A as the active system, if the line connection request signal 13A is not output, the master station apparatus 2A is not output.
A, if the line connection request signal 13A is output and the line connection signal 14A is not output, the line switching device 3
If both the line connection request signal 13A and the line connection signal 14A are output, it is possible to specify the location of the failure, such as a failure in the external communication line 10. Similarly, when the master station device 2B is communicating as the active system, the location where the failure has occurred can be specified.

[0017]

According to the present invention, since the line switching device switches the line in response to the line connection request signal output later, the line switching device can be reliably switched to the standby system even if a failure occurs in the active master station device. Can be switched. In addition, since communication is performed by capturing a line connection signal, when communication is interrupted, the location of occurrence can be specified, and restoration can be performed in a short time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a remote monitoring system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a last-in-first-out circuit in the line switching device in FIG. 1;

FIG. 3 is a time chart for explaining the operation of the last-in-time priority circuit.

FIG. 4 is a time chart for explaining the operation of the last-in-time priority circuit.

FIG. 5 is a configuration diagram of a conventional remote monitoring system.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 upper device, 2A, 2B master station device, 3 line switching device, 4 last-in priority circuit, 5 switch switch, 6 switch switch, 7 line connection signal source, 8A, 8B monitoring circuit, 9A, 9B: AND circuit, 10: Changeover switch, 1
1A, 11B: communication path, 12A, 12B: communication line, 1
3A, 13B: line connection request signal, 14A, 14B: line connection signal, 15: line switching signal, 16: external communication line, 17A, 17B: status signal, 18A, 18B: status signal, 19A, 19B: line switching signal , 20A, 20B
... D flip-flops, 21A, 21B ... one-shot pulse generation circuits, 22A, 22B ... one-shot pulse generation circuits, 23A, 23B ... line connection request signals, 24
A, 24B ... clear signal, 25 ... line switching signal, 26 ...
AND circuit.

Claims (1)

[Claims] A plurality of slave station devices are connected to a duplicated master station device via a line switching device via an external communication line such as a public line, and the master station device is connected to various slave station devices. In a remote monitoring system in which a monitoring signal is collected and a higher-level device and a master station device are connected by communication, and the collected monitoring signal is transferred, the master device is an active system depending on the presence or absence of communication from the higher-level device. A means for determining whether there is a standby system or a standby system, a means for outputting a line connection request signal when the system is the active system, and after confirming that the communication line of the own device is connected to the external communication line, Means for performing communication, the line switching device automatically connects the communication line of the master station device to which the line connection request signal is output to an external communication line, and outputs a line connection signal to the master station device. Means to do and parents Means for connecting the master station, which outputs the subsequently output line connection request signal, to the external communication line when the device outputs the line connection request signal. Remote monitoring system.