JPH07101883B2 - Redundant loop back system - Google Patents

Description

TECHNICAL FIELD The present invention relates to a signal path duplication loopback system in which signal paths are duplicated in a loop communication network.

[Conventional technology]

As this type of system, there is a conventional system, for example, JP-A-62-98839.
It was disclosed in the issue.

This is because in an optical loop transmission system with dual signal transmission lines, both transmission lines are cut, and when a supervision node instructs reconfiguration, normal optical signals have arrived for both systems. In this case, each communication node should be in a forward state where it sends a signal to the downstream of the same system as the receiving system, and if a normal optical signal does not arrive from one system or both systems, both systems should receive. It is in a loopback state that sends a signal to the downstream side of the system opposite to the system.
A node that is in a loopback state transmits from upstream to downstream when a normal optical signal arrives for each route that is looping back, but otherwise transmits to downstream. Is configured to stop. Then, by performing such an operation, in each communication node, after the transient state of the optical path selection logic due to the difference in optical signal arrival time has passed, the failure point is isolated and the system reconfiguration is completed.

[Problems to be Solved by the Invention]

However, in this method, even if communication is impossible due to an abnormality in the signal path, each communication unit enters the loopback detection operation of the signal path only after the reconfiguration instruction data is transmitted from the monitoring node. . Therefore, since the reconfiguration instruction data is required to perform the reconfiguration, there is a problem that the system configuration becomes complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a signal path duplication loopback system that can reconfigure a transmission path with a simple configuration without requiring special instruction data when an abnormality occurs in the signal path.

[Means for Solving the Problems]

Therefore, in the present invention, when a plurality of unit groups are coupled in a loop via a signal path that is duplicated by a main transmission system and a sub-transmission system, and an abnormality occurs in the signal path or the unit. , In a signal line duplex loopback system that reconfigures a transmission system by performing loopback, when normal, data is transmitted to the main transmission system and a dummy is transmitted to the sub transmission system in a direction opposite to the transmission direction of the data. The unit group is configured to transmit data.
A master control unit and a plurality of terminal units are included, and the master control unit has means for sending a first abnormality detection signal to a signal path on the downstream side of the main transmission system when detecting an abnormality of the main transmission system. , The master control unit and the terminal unit each stop sending dummy data to the signal path on the downstream side of the sub-transmission system when detecting that the data on the signal path on the upstream side of the main transmission system is disrupted. However, the first switching means for connecting the signal path on the upstream side of the sub transmission system and the signal path on the downstream side of the main transmission system, and the dummy data in the signal path on the upstream side of the sub transmission system are interrupted. And a second switching means for sending the data received from the signal path on the upstream side of the main transmission path to the signal path on the downstream side of the sub transmission system. Each terminal unit, upon detecting that the data is interrupted, means for sending a second abnormality detection signal to the downstream signal path of the main transmission system, the second
According to the input of the abnormality detection signal, by switching the third switching means for connecting the signal path on the upstream side of the sub transmission system to the signal path on the downstream side of the main transmission system, and the first switching means. When the first abnormality detection signal is input from the upstream side of the main transmission system, the switching of the third switching means is canceled, and the upstream and downstream signal paths of the main transmission system are provided. And a fourth switching means for connecting to.

[Operation] According to the present invention, when an abnormality occurs in the main transmission system, the terminal unit (2b) of FIG. 3 sandwiching the abnormality occurrence point is provided with the first switching means (the signal detection circuit (5Ia), the three-state buffer ( 6,7) connects the signal line (4b) of the sub transmission system to the signal line (3b) of the main transmission system, and the terminal unit (2a).
Since the dummy data cannot be received, the second switching means connects the signal path (3d) of the main transmission system to the signal path (4d) of the sub transmission system. The terminal unit (2
b) sends the second abnormality detection signal, so that in the terminal unit located in the middle, the third switching means (signal detection circuits 5Ia, 5IIa, three-state buffers 6, 7) are activated by the second abnormality detection signal, The sub-transmission system signal path (4c) is connected to the main transmission system signal path (3c).

When the master control unit (1) detects an abnormality in the main transmission system, it sends a first abnormality detection signal to the signal path (3d) of the main transmission system. The terminal unit (2a) sends the first abnormality detection signal to the signal path (3a) on the downstream side, but does not reach the terminal unit (2b) due to the disconnection abnormality. In the terminal unit (2a), the signal detection circuit (5Ib) and the three-state buffer (8) connect the upstream signal path (3d) of the main transmission system to the downstream signal path (4d) of the sub signal system. 1 Abnormality detection signal is sent back. At this time, the three-state buffer (9) becomes high impedance, and the upstream and downstream signal paths of the sub transmission system are disconnected.

In the terminal (2c) located in the middle, since the second abnormality detection signal is input from the upstream of the signal path (3b) of the main transmission system, the three-state buffer (10) is in the operating state.
Therefore, the terminal unit (2c) that receives the return first abnormality detection signal from the signal path (4c) of the sub-transmission system is detected by the signal detection circuit (5Ib), which causes the three-state buffer (9) to operate. Become. The first abnormality detection signal is returned by the terminal unit (2b) and is input from the upstream side (3b) of the main transmission system of the intermediate terminal unit (2c).

As a result, the three-state buffer (8) has a high impedance and the three-state buffer (9) operates to release the connection state by the third switching means, and the loop shown in FIG. 3 (c) is reconstructed. It

In the communication terminal unit (2b), since the first abnormality detection signal and the second abnormality detection signal are not input from the upstream side, the three-state buffer (10) is in a high impedance state, and the signal path (4b) on the upstream side of the sub transmission system The signal path (4a) on the downstream side is not connected (see FIG. 3 (B)). As a result, the communication terminal (2a) cannot input the first abnormality detection signal from the signal path (4a) on the upstream side of the sub transmission system, so that the signal path (4a) on the upstream side and the signal path on the downstream side (4a) of the sub signal system ( 4a) and the downstream signal path (4a) are not connected. From the above, even if all terminals make a double loop loopback connection when an abnormality is detected, the master control unit (1)
The return connection of the intermediate terminal unit can be released by the (first) abnormality detection signal generated from the.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the configuration of the signal line duplex loopback system of the present invention. Here, 1 is a master control unit, and 2a to 2c are communication terminal units, which are connected in a loop through redundant signal paths, that is, main signal paths 3a to 3d and sub signal paths 4a to 4d. In addition, the signal paths 3a to 3d, 4
a to 4d may be optical transmission lines or electric signal transmission lines. During normal communication, communication data is sent to the main signal paths 3a to 3d and dummy data is sent to the sub signal paths 4a to 4d.

FIG. 2 shows a configuration of a signal path switching device according to an embodiment of the present invention, which is arranged in each unit 1 and 2a to 2c.

Here, 5 is an internal circuit of a master control unit (hereinafter abbreviated as master) 1 or a communication terminal unit (hereinafter abbreviated as terminal) 2a to 2c. 5Ia and 5IIa are signal detection circuits connected to the main signal paths 3a to 3d, and 5Ib is a sub signal path 4
Signal detection circuit connected to a to 4d, 52 is signal detection circuit 5IIa
An inverter that inverts the output of the NAND gate, 54 is a NAND gate that receives the inverted output and the output signal of the signal detection circuit 5Ib as input signals, and 53 is the inverted signal of the NAND output and the inverted signal of the output of the signal detection circuit 5Ia. It is an OR gate used as a signal.

7 and 6 are 3-state buffers controlled by the output of the OR gate 53 and its inverted signal,
The sub signal path or the main signal path is connected to the internal circuit 5 by the control. Reference numeral 8 is a 3-state buffer controlled by the inverted signal of the output of the signal detection circuit 5Ib, and the output line of the internal circuit 5 is connected to the sub signal path by the control.
Further, 9 and 10 are 3-state buffers provided in the sub-signal path, which are controlled by the signal detection circuits 5Ib and 5Ia, respectively.

At the time of abnormality (signal line break), each unit 1 or 2a to 2c detects this and sends an abnormality detection signal. In each of the terminals 2a to 2c, each internal circuit 5 outputs an abnormality detection signal (terminal abnormality detection signal) when the input from the main signal path is interrupted, and in the master 1, the communication data sent to the main signal path 3d by itself is transmitted. When no signal is input from the main signal path 3c even after a lapse of a predetermined time, it is determined to be abnormal and an abnormality detection signal (master abnormality detection signal) is output. Here, the master 1 and the terminals 2a to 2c have different pulse frequencies (master frequency> terminal frequency).

In FIG. 2, the signal detection circuit I (5Ia, 5Ib) determines that there is a signal regardless of which pulse is received, and the signal detection circuit II (5II) is transmitted from the master 1. It is judged that there is a signal for the abnormality detection signal, but the terminal
A function to determine "no signal" is provided for the abnormality detection signals 2a to 2c. That is, the signal detection circuit I determines "no signal" only when no signal is received, and the circuit II determines "no signal" when the frequency of the abnormality detection signal of the terminal is less than or equal to the frequency. These detection circuits can be configured by combining appropriate logic circuits such as flip-flops and counter circuits.

The dummy data has the same frequency as the abnormality detection signals of the terminals 2a to 2c. The abnormality detection signal of each unit is
Stop output when loop is established.

The operating ranges of the detection circuits I and II are as shown in the following table.

At the time of normal communication, all of the signal detection circuits I and II shown in FIG. 2 determine that "there is a signal" and output "H". Therefore, as for the three-state buffers, those indicated by reference numerals 6, 9 and 10 are in operation.

Next, an example of processing at the time of abnormality will be described.

(At the time of abnormality 1) When disconnection occurs in the main signal path 3a (3rd
Figure).

In the terminal 2b, no data comes from the main signal path 3a, so the detection circuit 5Ia determines that "no signal" and sets the output to L level. Therefore, in the normal state, the data that was fetched from the main signal path 3a to the internal circuit 5 is switched to fetch the data from the sub signal path 4b, and the dummy data transmission to the sub signal path 4a is stopped. (3 in Fig. 2
State buffer 7 is operating, 6 and 8 are in high impedance state. Then, the terminal abnormality detection signal is sent to the main signal path 3b. That is, at this time, the signal flow in the terminal 2b is as shown in FIG.

Since the terminal 2a cannot receive dummy data at all due to the stop of the transmission to the sub-signal path 4a of the terminal 2b, the detection circuit 5Ib
Determines that there is no signal, and after a predetermined time, switching is performed so that the data from the internal circuit 5 that was sent to only the main signal path 3a in the normal state is also sent to the sub signal path 4d (3
The state buffer 8 is in an operating state and 9 is in a high impedance state. Further, in the terminal 2c, the signal detection circuit 5Ia determines that "there is a signal" according to the abnormality detection signal from the terminal 2b, and
A level signal is output, and the circuit 5IIa determines that "no signal" and outputs an L level signal. As a result, the sub-signal path 4c
The switching is performed so that the data from (3) is also taken into the internal circuit 5 (the 3-state buffer 7 operates, 6 is in a high impedance state). At this time, the connection state of signals in the terminals 2a and 2c and the signal flow in the system are shown in FIG. 3 (B).
As shown in.

On the other hand, the master 1 judges that there is no data input within a predetermined time and sends a master abnormality detection signal to the main signal path 3d. This signal is returned at the terminal 2a and input to the terminal 2c via the sub signal paths 4d and 4c. In the terminal 2c, the signal detection circuit 5Ib determines that “there is a signal”, and thus continues to output the H level signal. Further, the master abnormality detection signal is input to the terminal 2b via the sub signal path 4b, returned here, and input to the terminal 2c via the main signal line 3b. At this time, the signal detection circuit of the terminal 2c
Both 5Ia and 5IIa output an H level signal, and in response thereto, switching is performed so that data is input from the main signal path 3b (three-state buffer 6 is operating, 7 is in a high impedance state).

At this time, the signal connection state inside the terminal 2c is shown in FIG.
Then, the reconstruction of the signal loop is completed.

Since the terminal 2a continues to send data to the main signal path 3a, it becomes possible to immediately return to the normal loop when the signal path is restored.

(At the time of abnormality 2) When the signal line is broken at two points (4th
Figure).

As shown in FIG. 4, when a disconnection occurs in the main signal path 3a and the sub signal path 4b, in the terminal 2b, no data comes from both the main and sub signal lines, so that the detection circuits are all "no signal". "
And the 3-state buffers 6 and 8 are operating,
A high impedance state is established and a terminal abnormality detection signal is sent to the main signal path 3b.

Next, since no data is transmitted from the sub-signal line 4a to the terminal 2a, the signal is returned as in the abnormal condition 1 as described above.

Further, the terminal 2c, since only the abnormality detection signal of the terminal is sent from the main signal path 3b, its detection circuit 5Ia determines "signal present", 5IIa "no signal", also from the sub-signal path 4c Since a signal including the abnormality detection signal of the master 1 (dummy data before the terminal 2a returns) is sent, the detection circuits 5Ib both determine that there is a signal. And 3
The state buffers 7 and 9 are in operation, and the state buffers 6, 8 and 10 are in a high impedance state. Therefore, the terminal 2c folds back the signal as shown in FIG. 4, and the reconfiguration of the signal loop is completed.

Since the signal from the sub-signal path 4c is also sent to the sub-signal path 4b as it is, the terminal 2b can automatically join the loop when the sub-signal path 4b is restored.

As described above, even when the signal line disconnection occurs in a plurality of parts, the loop can be reconfigured in the communicable portion including the master 1, and the signal line abnormality can be prevented from spreading to the entire system. Note that the loop can be reconfigured in the same manner when the power supply to the terminal unit is cut off.

It should be noted that the number and types of units that configure the system are not limited to the above examples, and it goes without saying that they are arbitrarily desired.

〔The invention's effect〕

As described above, according to the present invention, each of the communication terminal unit and the master control unit is provided with a signal detection circuit for an abnormal output signal and a dummy data generating means, and the output signal at the time of abnormality is used as a master control unit. Since the occurrence frequency is different from that of the communication terminal unit, abnormality detection and signal loop reconfiguration can be easily performed for each communication unit without requiring reconfiguration instruction data and the like.

Further, even when the signal lines of a plurality of parts are broken, the loop can be reconfigured in the communicable portion including the master 1 to prevent the abnormality of the signal line from spreading to the entire system.
Further, even when a failure occurs in the power supply of the terminal unit, the loop can be reconfigured in the same manner.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration example of a signal path duplex loopback system to which the present invention is applicable, and FIG. 2 is an internal configuration of a unit shown in FIG. 1 including a signal path switching device according to an embodiment of the present invention. 3 is a block diagram showing an example, FIGS. 3 (A) to 3 (C) are explanatory views showing a signal path reconfiguration aspect in the system of FIG. 1 at the time of an abnormality (example of disconnection at one place), and FIG. 4 is FIG. FIG. 5 is an explanatory diagram showing a signal path reconfiguration aspect in the case of an example of disconnection at two places in the system of FIG. 1 ... Master control unit, 2a-2c ... Communication terminal unit, 3a-3d ... Main signal line, 4a-4d ... Sub-signal line, 5Ia, 5Ib ... Signal detection circuit I, 5IIa ... Signal detection circuit II, 6-10 ... 3-state buffer.

Claims (1)

[Claims] 1. A plurality of unit groups are connected in a loop through a signal path that is duplicated by a main transmission system and a sub-transmission system, and when an abnormality occurs in the signal path or the unit, a loop is formed. In a signal line duplex loopback system that reconfigures the transmission system by performing back, normally, data is transmitted to the main transmission system and dummy data is transmitted to the sub transmission system in the opposite direction to the transmission direction of the data. When not transmitting, the unit group includes a master control unit and a plurality of terminal units, the master control unit, when detecting an abnormality of the main transmission system, to a signal path on the downstream side of the main transmission system. 1 has a means for sending out an abnormality detection signal, each of the master control unit and the terminal unit of the signal path on the upstream side of the main transmission system. When detecting the interruption of the data, the dummy data transmission to the signal path on the downstream side of the sub transmission system is stopped, and the signal path on the upstream side of the sub transmission system and the signal path on the downstream side of the main transmission system are stopped. And a first switching means for connecting to the first transmission means, and detecting that the dummy data in the signal path on the upstream side of the sub-transmission system is broken, the data received from the signal path on the upstream side of the main transmission path is A second switching means for sending the signal to the signal path on the downstream side of the sub transmission system, and each of the terminal units detects a signal on the downstream side of the main transmission system when detecting the interruption of the data. Means for sending a second abnormality detection signal to the path, and a signal path on the upstream side of the sub transmission system to a signal path on the downstream side of the main transmission system in response to the input of the second abnormality detection signal. Third switching means to be connected, and the first switching means When the first abnormality detection signal is input from the upstream side of the main transmission system by switching, the switching of the third switching means is canceled, and the upstream signal path and the downstream signal of the main transmission system are released. Fourth connecting to the road
A signal path duplication loopback system having a switching means.