JPH07212277A - Line switching system - Google Patents

Abstract

PURPOSE:To improve the reliability of switching from the active side by monitoring normality on the reserve side at all times by conducting the loop- back of a non-active side communication system at a counter line switching device and forming a loop. CONSTITUTION:When a switching signal is '0', the communication with the opposite side is performed on the active side by connecting a first interface 101 to a third interface 103 and connecting a second interface 102 to a fourth interface 104. On the other hand, a sixth interface 106 is connected through a logic circuit 114 to a fifth interface 105, and the reserve side forms the loop with the counter station. When the switching signal is '1', the communication with the opposite station is conducted on the reserve side by connecting the first interface 101 to the fifth interface 105 and connecting the second interface 102 to the sixth interface 106. Then, the fourth interface 104 is connected through a logic circuit 113 to the third interface 103, and the active side forms the loop.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line switching system for controlling switching between an active communication system and a standby communication system, and more particularly to a line switching system which is compact and economical, and which performs stable switching operation. Regarding switching system.

In recent years, the ratio of on-line data and images in the information transmitted and received via a communication system has been increasing, mainly from telephone voice, and the reliability required for the communication system has become higher. Is coming.

One implementation method for configuring a communication system having high reliability is to provide the communication system with redundancy. One method for providing redundancy is 1 for n lines.
A backup line fixed line is provided, and when a failure occurs in the operating line, the line is switched to the backup line, and when the failure is recovered, the backup line is fixed and the original line is fixed n: 1 switching system,
Normally, n lines out of the (n + 1) lines are used, and if one of the n lines fails, switch to the unused line, and failback is possible even if the failed line is restored. It is a form of the n: 1 switching method in which the backup line is not fixed and the standby line is fixed until the next line failure occurs, or the n: 1 switching system in which the backup line is fixed. One method is to provide one line and switch to the protection line when the working line fails.

Although there are several factors in selecting the above method, the economic priority of the system is the highest priority. In a system in which a cable forming a relay transmission line is expensive, or a number of required repeaters is large, or in a system such as a wireless communication system in which usable frequencies are limited, or is used. On the other hand, in a system in which the cable forming the relay transmission path is inexpensive and the repeater span is long, it becomes possible to adopt. Since the optical communication system exactly satisfies this condition, the line switching system of the working 1 and the backup 1 is generally adopted. Also, this working one,
The line switching system of the spare 1 has an advantage that switching control is simple.

If the communication line is duplicated and the working line is switched to the protection line when the failure occurs, the reliability of the communication line can be improved.
It is realized only when the protection line operates normally. Therefore, in the line switching system, the function of monitoring the protection line is important.

[0006]

2. Description of the Related Art FIG. 12 shows the configuration of a conventional line switching system. In FIG. 12, 1'is a first line switching device, 1'a is a second line switching device, 2 is a first transmission device that is not duplexed, 2a is a second transmission device that is not duplexed, 3a Is a third transmission device that constitutes the active communication system, 3a is a fourth transmission device that constitutes the active communication system, 4 is a fifth transmission device that constitutes the standby communication system,
Reference numeral 4a is a sixth transmission device which constitutes a backup communication system. Further, 18 and 18a are pattern generators, 19 and 1
9a is a pattern detector.

When the working side is operating normally, the first transmission device and the second transmission device are connected to the working side of the transmission devices duplicated by the line switching devices 1'and 1'a to communicate. is doing. A pattern generator and a pattern detector provided in the line switching device are connected to the protection side, and the protection line is monitored oppositely. By doing this, it is always confirmed that the spare side is operating normally, so if a failure occurs on the working side, normal operation starts immediately and damage due to the failure is prevented. It is held to a minimum.

Then, when switching to the spare mode, the pattern generator and the pattern detector are connected to the working side and used for fault search on the working side, and when the fault is recovered, it is finally confirmed that the working side is normal. Used to. After that, the spare side is switched to the working side (this is called switchback).

FIG. 13 is a diagram showing a configuration of a conventional line switching device, in which a connection form in which the working side is operating is represented by a thick line. In FIG. 13, 101 is the first interface on the non-duplex side, 102 is the second interface on the non-duplex side, 103 is the third interface on the working side, 104 is the fourth interface on the working side, 105 is the fifth interface on the spare side, 1
06 is the sixth interface on the spare side, 121 to 1
Reference numeral 24 is a selection circuit, 18 is a pattern generator, and 19 is a pattern detector. A switching signal that rises to "1" at the time of switching and returns to "0" at the time of switching back is applied to the control terminal of each selection circuit.

Since FIG. 13 shows a connection state in which the working side is in operation, the switching signal is "0". Therefore, the first interface is connected to the third interface via the selection circuit 121, the second interface is connected to the fourth interface via the selection circuit 122, and the pattern generator is connected via the selection circuit 123. Connected to the fifth interface, the pattern detector has a selection circuit 124.
Connected to the sixth interface via. If the switching signal becomes "1", the respective selection circuits select different input terminals, so the first and second interfaces are connected to the fifth and sixth interfaces on the spare side, and the pattern generator. The pattern detector is connected to the third and fourth interfaces on the working side.

However, in the configuration of FIG. 13, the line switching device requires the pattern generator and the pattern detector, and the pattern generator and the pattern detector are large in size as compared with the selection circuit. However, there is a problem that the price is raised and the scale of the line switching device is increased.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a line switching system, which can cope with such a problem and can be realized at a low cost on a small scale and which has a stable switching control function.

[0013]

FIG. 1 illustrates the principle of the present invention. In FIG. 1, 1 is a first line switching device, 1a is a second line switching device facing the first line switching device, 2a
Is a first transmission device that is not duplexed, 2a is a second transmission device that is not duplexed, 3 is a third transmission device that constitutes an active communication system, and 3a is a fourth transmission device that constitutes an active communication system Reference numeral 4 is a fifth transmission device that constitutes the backup communication system, and 4a is a sixth transmission device that configures the backup communication system.

[0014]

In FIG. 1, the thick line and the broken line in the block of the line switching device indicate the logical connection of the line switching device. When the working side is operating, the first transmission device transmits the third transmission signal. In the device, the second transmission device is connected to the fourth transmission device, the reception output of the fifth transmission device is folded back in the first line switching device and connected to the transmission input of the fifth transmission device. The reception output of the sixth transmission device is folded back in the second line switching device and connected to the transmission input of the sixth transmission device. That is, the spare side forms a loop by the first and second line switching devices.

Since the fifth and sixth transmission devices, which are the transmission devices on the standby side, have various monitoring functions and alarm functions based on them, they can be used to constantly monitor the normality on the standby side. The reliability of switching from the working side can be improved.

[0016]

EXAMPLE FIG. 2 shows an example of the present invention. In FIG. 2, 101 is the first interface on the non-duplex side, 102 is the second interface on the non-duplex side, 103 is the third interface on the active side, and 104 is the fourth interface on the active side. Interface, 105 is a fifth interface on the spare side, 106
Is the sixth interface on the spare side, 111 and 112
Is a selection circuit, and 113 and 114 are AND circuits.

In the configuration of FIG. 2, the switching signal is "0".
At this time, the first interface is connected to the third interface and the second interface is connected to the fourth interface, and communication with the opposite station is performed on the working side.
Further, the sixth interface is connected to the fifth interface via the AND circuit 114, and the spare side forms a loop with the opposite station.

On the other hand, when the switching signal is "1", the first interface is connected to the fifth interface and the second interface is connected to the sixth interface, and the spare side communicates with the opposite station. Further, the fourth interface is connected to the third interface via the AND circuit 113, and the working side forms a loop with the opposite station.

Since the communication system of the loop side confirms the normality by its own monitoring function and prepares for switching or switching back, the reliability of switching or switching back is improved.

However, in the configuration of FIG. 2, when the switching time is shorter than the delay time of the loop between the two switching devices, it is possible to repeat the occurrence and recovery of errors in the communication system in the loop. is there. This is because when the switching time is shorter than the delay time of the loop, the communication signal remains on the loop after switching, so if a momentary disconnection occurs during switching and the communication signal is incorrect, it will be inserted for error verification. This is because the result of the calculation using the communication signal at the current position differs from the result of the same calculation using the current communication signal, and the monitoring function in the communication system is considered to be abnormal. Moreover, since this phenomenon continues once the loop is formed, the communication system on the loop side is judged to be abnormal even if the communication system on the loop side is normal, and switching back or switching can be performed thereafter. The second embodiment of the present invention described below solves such an inconvenience.

Before touching on the details of the second embodiment of the present invention, its principle will be explained. 3A and 3B are diagrams for explaining the operation of the active system when forming a loop. FIG. 3A shows the operation when the fixed pattern is inserted before forming the loop, and FIG. 3B shows the operation after the loop is formed. .

In FIG. 3, 1 is a first line switching device,
Reference numeral 1a is a second line switching device, 3 is a third transmission device which constitutes an active communication system, and 3a is a fourth transmission device which constitutes an active communication system. Before forming the loop,
The fixed pattern is forcibly inserted for a predetermined time via the selection circuit of each line switching device. This fixed pattern causes the third and fourth transmission devices to lose synchronization, and the third and fourth transmission devices send out the AIS signal.
The AIS signal is received by the fourth and third transmission devices and A
When the IS signal is detected and is sent again, the AIS signal is inserted. If the switching time is set longer than the delay time of the loop, when the selection circuit of each line switching device is operated to form the loop, no communication signal exists on the loop and only the AIS signal is inserted. Signal continues to go around the loop, and the above-mentioned inconvenience is eliminated.

Although the above is the operation at the time of switching, a dual operation is also performed at the time of switching back. 4A and 4B are time charts of the switching operation. FIG. 4A shows the switching operation and FIG. 4B shows the switching back operation.

FIG. 5 shows the configuration of the switching device according to the second embodiment of the present invention, and shows the first and second switching devices facing each other. In FIG. 5, 101 and 101a are the first interfaces on the non-duplex side, 102 and 102a are the second interfaces on the non-duplex side, and 103 and 103a are the third interfaces on the duplex side, 104. And 104a are the fourth interfaces 105 and 105 on the duplexed side.
a is the fifth interface on the duplicated side, 1
Reference numerals 06 and 106a denote a sixth interface on the duplicated side, 11 and 11a to 15 and 15a denote first to fifth selection circuits for selecting one of two inputs, 16
Reference numerals 16a and 16a are first timer circuits that generate a pulse of a predetermined time when the switching signal rises, and 17 and 17a are second timer circuits that generate a pulse of the predetermined time when the switching signal falls. In the first selection circuit, the first input terminal is connected to the sixth interface, the second input terminal is connected to the fourth interface, the output terminal is connected to the second interface, and the switching signal is supplied to the control terminal. In the second selection circuit, the first input terminal is the output terminal of the first timer circuit, the second input terminal is the fourth interface, and the output terminal is the third selection circuit described later. One input terminal is connected, the control terminal supplies the output signal of the first timer circuit, the third selection circuit, the first input terminal to the output terminal of the second selection circuit, the second Input terminal Said first interface,
The output terminal is connected to the third interface, the switching signal is supplied to the control terminal, the fourth selection circuit, the first input terminal is the output terminal of the second timer circuit, the second input terminal Is connected to the sixth interface, the output terminal is connected to the second input terminal of the fifth selection circuit described later, and the control terminal is supplied with the output signal of the second timer circuit,
In the fifth selection circuit, the first input terminal is connected to the first interface, the second input terminal is connected to the output terminal of the fourth selection circuit, the output terminal is connected to the fifth interface, the control terminal Is supplied with a switching signal, and the first and second timer circuits are supplied with a switching signal.

6 to 9 show the time chart of FIG.
Time t₁To t_FourLine switching system connection compatible with
FIG. 6 is a diagram showing when the active system is in operation (time t
₁), At the start of switching (time t₂), Figure 8 is switching
(Time t₃), FIG. 9 shows the completion of switching (time t₃) Connection
is there. The connections shown in bold are carrying valid signals
Is. Since the figure is easy to understand, detailed description is omitted.
At the start of switching (time t ₂) To the second selection circuit of station A
Fixed station output from the first timer circuit of station A via
The turn is designed to be inserted. Also, during switching (hour
Tick t₃) To the first station of B station via the second selection circuit of B station
The fixed pattern that is the output of the timer circuit is inserted
It is like this. At this time, at Station A, the 4th interchange
Loopback from face to third interface
The communication path has already been switched to the backup side. Change
At the completion of switching (time t_Four), Station B has a loopback
Is complete and the working side is in a loop.

Next, regarding the connection in the case of switching back, FIG. 9 shows when the backup side is in operation (time T ₁ ), FIG. 10 shows when switching back starts (time T ₂ ), and FIG. 11 shows switching back. (Time T ₃ ) and FIG. 6 shows the connection at the time of completion of the switchback (Time T ₄ ). Since this is a dual of the above description of FIGS. 6 to 9, it is only shown in the figure and the description is omitted.

[0027]

As described above, according to the present invention, a line switching device capable of confirming the normality of a switching destination system is realized at a small scale and at a low price, and further, there is a problem that may occur with switching. It can be resolved. This allows
The reliability of the line switching system can be greatly improved, and it becomes possible to meet the demand for higher reliability of the communication system.

[Brief description of drawings]

FIG. 1 is a principle of the present invention.

FIG. 2 is an embodiment of the present invention.

FIG. 3 shows the operation of the active system when forming a loop.

FIG. 4 is a time chart of a switching operation.

FIG. 5 is a configuration of a line switching device according to a second embodiment of the present invention.

FIG. 6 When the current system is in operation (when the switchback is completed).

FIG. 7 At the start of switching.

[Fig. 8] Switching is in progress.

FIG. 9 When switching is completed (when the backup side is operating).

[Fig. 10] At the start of switching back.

FIG. 11 is being switched back.

FIG. 12 is a conventional line switching system.

FIG. 13 is a configuration of a conventional line switching device (when the working side is in operation).

[Explanation of symbols]

 1 1st line switching device 1a 2nd line switching device 2 1st transmission device 2a 2nd transmission device 3 3rd transmission device 3a 4th transmission device 4 5th transmission device 4a 6th transmission apparatus

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyasu Ogawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (3)

[Claims] 1. A line switching system for performing switching control between an active communication system and a standby communication system, wherein a communication system (4, 4a) on the non-operation side has a loopback in an opposing line switching device (1, 1a). Then, a line switching system characterized by forming a loop. 2. The switching system according to claim 1, wherein the switching time from the start of switching to the completion of switching is set longer than the delay time of the loop, and during the switching time, a fixed pattern is set by the line switching device. A line switching system characterized by transmitting signals. 3. The switching system according to claim 1, wherein the switching device is the first interface (10) on the non-duplex side.
1), the second interface (102), the third interface (10) on the duplicated side
3), the fourth interface (104), the fifth interface (105), the sixth interface (1
06), first to fifth selection circuits (11, 12, 13, 14, 15) for selecting one of the two inputs, and a first timer circuit (16) for generating a pulse for a predetermined time when the switching signal rises. ), A second timer circuit (17) for generating a pulse of the predetermined time at the fall of the switching signal, the first selection circuit, the first input terminal to the sixth interface, the second input The terminal is connected to the fourth interface, the output terminal is connected to the second interface, the control signal is applied to the switching signal, the second selection circuit, the first input terminal is the first timer At the output terminal of the circuit,
A second input terminal is connected to the fourth interface, an output terminal is connected to a first input terminal of a third selection circuit described later, and a control terminal is connected to an output terminal of the first timer circuit, The first input terminal is connected to the output terminal of the second selection circuit, the second input terminal is connected to the first interface, the output terminal is connected to the third interface, and the control terminal is Applying a switching signal, the fourth selection circuit, the first input terminal to the output terminal of the second timer circuit,
A second input terminal is connected to the sixth interface, an output terminal is connected to a second input terminal of a fifth selection circuit described later, a control terminal is connected to an output terminal of the second timer circuit, The first input terminal is connected to the first interface, the second input terminal is connected to the output terminal of the fourth selection circuit, the output terminal is connected to the fifth interface, and the control terminal is connected to the first interface. A line switching system, characterized in that a switching signal is applied and the switching signal is supplied to the first and second timer circuits.