JPH0528934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control system for a transmission line in a loop network in which transmission lines are duplicated.

(Prior art and its problems) FIG. 13 is a diagram showing a general configuration of a duplex loop network. In the figure, nodes 1, 2, 3, 4, 5, and 6 are connected by duplex transmission paths, that is, a first transmission path 100 and a second transmission path 200, taking into account transmission path failures. . Usually, the first transmission line 100 and the second
The same signal is transmitted in the opposite direction to the transmission line 200 of . That is, as shown in the figure, the signal from the input terminal 11 of the first transmission line 100 at the node 5 is also transmitted to the output terminal 12 of the first transmission line 100.
is relayed to the input terminal 21 of the second transmission line 200.
The signal from is also relayed to the output terminal 22 of the second transmission line 200. During normal use, only one of the transmission lines is used, and if a failure occurs in the transmission line in use, the other transmission line is used.

For example, as shown in FIG. 14, if a failure occurs in the transmission path between nodes 3 and 4, node 3
, the input terminal 11 of the first transmission line 100
The signal from the output terminal 22 of the second transmission path 200
At node 4, the second transmission path 20
The signal from the input terminal 21 of
It is relayed to the output terminal 12 of 0. Such a state of nodes 3 and 4 is called a loopback state. Various methods have been proposed for loopback control, but all of them are based on a method in which a node immediately downstream of a failure location detects a signal disconnection state and controls itself to loopback state. ing. However, when a failure occurs in the transmission path, all nodes located downstream of the failure location experience a signal cut-off state. Therefore, normally, the nodes that detect a signal disconnection cannot be limited to only the nodes immediately downstream of the location where the failure occurs. In order for the node directly downstream of the fault location to detect the fault first, it is necessary, for example, to set the time constant for detecting a signal disconnection state at the node to the same value at all nodes. However, such control is inefficient in terms of the quantity and quality of hardware.

(Objective of the Invention) The object of the present invention is to enable each node to detect the fault at an arbitrary time and perform loopback control when a fault occurs in the transmission link in a loop network having duplex transmission lines. The ultimate objective of the present invention is to provide a loop network transmission path control system that reconfigures transmission paths into a unique form.

(Structure of the Invention) According to the present invention, the control node includes one control node and a plurality of nodes, and these control nodes and nodes transmit signals in a direction opposite to the first transmission path and the first transmission path. looped by the second transmission line,
In the loop network connected in a duplex manner, the control node supplies a first control signal to the output terminal connected to the first transmission line, and supplies the first control signal to the output terminal connected to the second transmission line. The node includes a circuit that supplies a second control signal to a terminal, and a circuit that monitors an input terminal connected to both of the transmission lines and detects the control signal, and the node has an input terminal that is connected to both of the transmission lines. a circuit that monitors the control signal and detects the control signal, and in the case of the node, when either of the control signals is detected on either of the transmission lines by the detection circuit, the detection circuit detects the control signal on either of the transmission lines. The signal from the input terminal connected to is relayed via the output terminal connected to each transmission line,
If the control signal is not detected on either of the transmission lines, the signal from the input signal connected to the transmission line where the control signal is detected is transmitted through the output terminal connected to this transmission line. The second control signal is detected at the input terminal connected to the second transmission path at the control node. Along with being
When the state in which the second control signal is detected at the input terminal connected to the first transmission path continues for a certain period of time, the control signal transmitted to the output terminal of the two transmission paths The transmission line in which the same type of control signal is detected at the input terminal is set as the active transmission line, and the second control signal is detected at the input terminal connected to the first transmission line, and the second control signal is detected at the input terminal connected to the first transmission line.
If the state in which the first control signal is detected at the input terminal connected to the transmission path continues for a certain period of time, which of the first and second control signals supplied to both the transmission paths is detected. A loop characterized in that transmission of one of the control signals is stopped, and a signal is relayed to an output terminal connected to the transmission path for an input terminal connected to the transmission path where transmission of the control signal has been stopped. Network and transmission path control methods are obtained.

(Example) Examples of the present invention will be described below. In the loop network based on the present invention, as shown in FIG.
The transmission line 100 and the second transmission line 200 are connected as shown in the figure. The control node 1 supplies the control signal A to the output terminal 12 of the first transmission line 100, and supplies the control signal B to the output terminal 22 of the second transmission line 200 in the opposite direction. The other nodes are internally connected to relay these control signals as shown in the figure (internal control will be described later). The control node 1 detects the control signal A at the input terminal 11 of the first transmission line 100 and detects the control signal A at the input terminal 21 of the second transmission line 200 when no fault occurs in the transmission line. Signal B is detected. At this time, the control node 1 learns that both the first transmission line 100 and the second transmission line 200 can operate normally. Note that in order to prevent the control signal transmitted by itself from circulating among the signals input from the input terminals 11 and 21, the control node 1 controls the removes these control signals from the transmission path without relaying them to the output terminals 12 and 22. Therefore, even when the loopback is configured as shown in FIG. 8, the control signals sent from the control node 1 to the output terminals 12 and 22 and the control signals received at the input terminals 11 and 21 due to the loopback are There will be no interference.

1 and 2 show control nodes 1 and 2 of the loop network shown in FIG. 3, respectively.
FIG.

In the control node 1 shown in FIG. 1, a control signal A generated by a signal generator 108 is supplied to an output terminal 12 connected to a first transmission line 100 via a selector 105 and a transmitter 106. . When the control node 1 transmits the control signal A, the output of the signal generator 108 is outputted to the selector 105, and when the control node 1 transmits another signal, the content of the transmission signal 305 is outputted, and as described later, the output of the signal generator 108 is outputted. When relaying a signal from the selector 104 or in a loopback state, the output of the selector 104 is output.

Input terminal 11 connected to first transmission line 100
The signal from the upstream node input from the upstream node passes through the receiving section 102 and is input to the detecting section 103 that detects the control signals A and B, the selector 104, and the selectors 204 and 302. When the first transmission path 100 is normal, the detection unit 103 detects the control signal A, and upon receiving this notification, the control unit 301 that controls the connection state within the node
00 identifies it as available. Control unit 301
Instructs the selector 104 to output the output of the receiving section 102 when relaying the signal at the input terminal 11 to the output terminal 12.

Regarding the second transmission path 200, the first transmission path 1
The operations described for 00 are similarly performed.
That is, the signal generator 208 is connected to the second transmission path 20
The control signal B is supplied to the output terminal 22 connected to
02 and is input to a detection unit 203 that detects control signals A and B, as well as to selectors 204, 104, and 302. Detection unit 20
3 detects the control signal B and notifies the control unit 301 of this, and the control unit 301 identifies that the second transmission path 200 is usable. The control unit 301
If both of the second transmission paths 100 and 200 are able to operate normally, the first transmission path 100 is used, and the transmission signal 305 is sent to the first transmission path via the selector 105 and sent to the first
The selector 302 is instructed to transmit the received signal 304 to the first transmission path 100 and output the output of the receiving section 102 connected to the first transmission path 100 as the received signal 304 . In this way, other nodes are notified that communication will be performed using the first transmission path 100.

FIG. 2 is a diagram showing the configuration of nodes 2, 3, 4, 5, and 6. Compared to the control node, the only difference is that the signal generators 108 and 208 are not provided, and the other configurations are completely the same. be. Note that the detection unit 1
03 and 203 are control nodes 1 as described above.
The selector 302 has a function of detecting a signal that notifies the usage status of the transmission path (for example, communication is performed using the first transmission path 100) transmitted by the The signal from the receiving section 102 or 202 is outputted via the selector 105 or 205, and the content of the transmission signal 305 is sent to the first transmission path 1 via either the selector 105 or 205.
00 or the second transmission path 200.

The control unit 301 also connects the input terminals 11 and 21 to
When the detection units 103 and 203 notify that either AB control signal is being supplied, these signals are controlled to be relayed to the output terminals 12 or 22, respectively.

Control node 1 and node 2 as described above,
Based on the configurations 3, 4, 5, and 6, control when a failure occurs in the transmission path will be explained using an example.

4, 5 and 6 show the first transmission line 1
FIG. 2 is a diagram illustrating a case where a failure occurs between nodes 3 and 4 of Node 00 (the location indicated by an x in the diagram).
At this time, control signal A is no longer observed at any of control node 1 and nodes 4, 5, and 6. For example, assume that node 5 first detects the disconnection state of control signal A. When the control unit 301 learns that the control signal A is no longer detected at the input terminal 11 by the detection unit 103 in the node 5 shown in FIG.
Relay the signal as shown in the figure. That is, the signal at the input terminal 21 is sent to the receiving section 202 and the selector 2.
04 and 205 and the transmitting section 206 to the output terminal 22, and also relaying the signal of the input terminal 21 to the receiving section 202 and the selectors 104 and 1.
The signal is also relayed to the output terminal 12 via the transmitter 05 and the transmitter 106.

After this, at the node 6, the first transmission path 10
The control signal B reflected at the node 5 is observed at the input terminal 11 of the node 0, and the signal is relayed as shown. Next, as shown in FIG.
The control signal B on the transmission path 200 is looped back. Therefore, the control signal B returned by the node 4 is observed at the input terminal 11 of the node 5, and when the detection unit 103 in the node 5 detects this, it notifies the control unit 301, as shown in FIG. The signal can be switched rather than being relayed. In the above manner, the first
When a fault occurs in the transmission path 100, the state stabilizes as shown in FIG. 6 after a certain period of time, regardless of the order in which the disconnection state of the control signal A is detected in the nodes downstream from the fault location.

In the connection state of the transmission line as shown in FIG.
Since the control signal B is detected, it is determined that the transmission line can operate normally.

However, the control signal A is not detected at the input terminal 11 of the first transmission line 100, but the control signal B returned at the node 4 is detected. Therefore, it is determined that the first transmission path 100 is not connected in a loop, and each node is notified to use the second transmission path 200 for communication thereafter.

Furthermore, as explained above, if the fault is recovered by replacing the transmission line during use in the state shown in FIG.
is supplied. When the detection unit 103 in the node 4 detects this, the normal state as shown in FIG. Identify when it is ready for operation.

Figures 7, 8, 9, 10, and 11
The figure shows a first transmission line 100 and a second transmission line 2.
00 is a diagram for explaining control when a failure occurs in both.

In FIG. 7, the control signal A is no longer supplied to the nodes downstream from the fault location with respect to the signal flow of the first transmission line 100, that is, the nodes 4, 5, and 6 and the control node 1. At this time node 4
When the node 5 detects the disconnection state of the control signal A at almost the same time, the control signal B of the second transmission path 200 is looped back and relayed as shown in the figure. Further, the control signal B is no longer supplied to the nodes downstream from the failure location with respect to the signal flow of the second transmission path 200, that is, the nodes 2 and 3 and the control node 1. At this time, the node 3 first detects the relay state of the control signal B, and returns and relays the control signal A of the first transmission line 100 as shown in the figure. Therefore, from now on, the 8th
As shown in the figure, node 5 detects control signal B returned by node 4 and switches to relay it, while node 2 detects control signal A returned by node 3 and switches to relay it. Relay. That is, the control node 1 connects the input terminal 11 of the first transmission line 100 to the second transmission line 20 after a certain period of time.
The control signal B transmitted from the output terminal 22 of the second transmission line 200 is detected, and the control signal A transmitted from the output terminal 12 of the first transmission line 100 is detected at the input terminal 21 of the second transmission line 200. At this time, the control node 1 connects the first transmission path 100 and the second transmission path 20
0 is not connected in a loop. In this case, the control node 1 stops transmitting either one of the two control signals A and B and performs the following control. For example, as shown in FIG. 9, the transmission of the control signal B to the second transmission path 200 is stopped, and the signal at the input terminal 21 of the second transmission path 200 is transmitted to the receiving section 202 and the selector 20 shown in FIG.
4 and 205 and the transmitting section 206, the signal is relayed to the output terminal 22 of the second transmission path 200.

Therefore, as can be seen from FIG. 9, the control signal A on the first transmission path 100 transmitted from the control node 1 is looped back to the second transmission path 200 at the node 3, and then transmitted to the second transmission path 200 at the control node 1. 2 transmission line 2
00, is looped back to the first transmission path 100 at the node 4, and reaches the control node 1. The control node 1 connects the input terminal 11 of the first transmission line 100 to the output terminal 1 of the first transmission line 100.
The control signal A transmitted from 2 is detected, and it is identified that the transmission line is connected in a loop.
The node is instructed to communicate using the transmission path 100 of the node.

A method for recovering from a failure while the transmission path is in use as shown in FIG. 9 will be explained. As shown in FIG. 10, first, the first transmission line 100 is restored by replacing the transmission line or the like. (The part indicated by a circle in the figure) After this, the node 4 is supplied with the control signal A and switches to relay the signal as shown in the figure. Next, as shown in FIG. 11, the control node 1 supplies the control signal B to the second transmission line 200, and then restores the second transmission line 200. (The part marked with a circle in the figure). The control signal B is now supplied to the node 3, and the normal state as shown in FIG. 3 is restored.

Further, FIG. 12 is a diagram showing a case where a transmission path failure occurs adjacent to the control node 1. As described above, regardless of the order in which each node detects the disconnected state of the control signal A, after a certain period of time, the node 2 returns the control signal B, and the control node 1 returns the signal, forming a loop.

In other words, in the control node 1 shown in FIG.
and relays the same signal to the output terminal 12 via the transmitting section 106 and transmits the same signal to the selectors 204 and 20.
5 and the transmitter 206 to the output terminal 22. Note that during this relay, the control signal B transmitted by itself is removed and only other signals are relayed. This is to prevent its own transmission signal from circulating on a loop.

(Effects of the Invention) As described above, in the present invention, when a failure occurs, the transmission path is maintained in a constant connection state after a certain period of time, regardless of the order in which failures are detected in each node. Moreover, since each node detects only the signal supplied to itself and performs its own control, it can be realized with simple hardware.

Furthermore, the control node 1 supplies two types of control signals to the transmission line, monitors only the state of the control signal input to itself, grasps the connection state of the entire transmission line, and communicates with the nodes in order to perform control. Communication control can also be simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a control node 1, FIG. 2 is a diagram showing the configuration of nodes 2, 3, 4, 5, and 6, and FIG. 3 is a diagram showing the configuration of a loop network based on the present invention. 4th, 5th, 6th, 7th, 8th, 9th, 10th, 1st
Figures 1 and 12 are diagrams showing the state of control when a failure occurs;
13 and 14 are diagrams showing control of a loop network based on the prior art. In the figure, 1 is a control node, 2, 3, 4,
5 and 6 are nodes, 11 and 12 are input terminals, 100
and 200 are first and second transmission lines, 102, 2
02 is a receiving section, 103, 203 is a detecting section, 10
4, 105, 204, 205, 302 are selectors, 106, 206 are transmitting units, 108, 208 are signal generating units, 301 is a control unit, 304 is a received signal, and 305 is a transmitted signal.

[Claims]

1. In a loudspeaker telephone that has a microphone and a speaker and whose transmitting and receiving states are switched and controlled by comparing the transmitting and receiving audio levels, a transmitting gain control circuit is inserted into the transmitting signal path connected to the microphone, and the speaker A receive signal gain control circuit is inserted into the receive signal path connected to the receiver, and a volume adjuster for adjusting the loudspeaker receive volume from the speaker is inserted, and the receive signal is attenuated by adjusting the volume adjuster. A sound volume control device for a loudspeaker telephone, which increases a transmission gain of the transmission gain control circuit in inverse proportion to an amount of attenuation.

Claims (1)

If the state in which a control signal is detected continues for a certain period of time, one of the two transmission lines, on which the same type of control signal as the control signal sent to the output terminal is detected at the input terminal, is selected as the active transmission line. a transmission line, and the second control signal is detected at an input terminal connected to the first transmission line, and the first control signal is detected at an input terminal connected to the second transmission line. If this state continues for a certain period of time, stopping the transmission of either one of the first and second control signals supplied to both transmission lines,
A transmission line control method for a loop network, characterized in that, for an input terminal connected to a transmission line where transmission of the control signal has been stopped, a signal is relayed to an output terminal connected to the transmission line.