JPH01149634A - Line switching device - Google Patents

Abstract

PURPOSE:To prevent wrong switching between the currently used and the standby lines before the bits and phases of the signals respectively become coincident with each other between the lines even under a condition where a fault tends to occur on one and the same currently used line immediately after a faulty state is restored by delaying the sending of pilot signal detected results. CONSTITUTION:Since a delaying circuit 4 outputs a detect signal 107 after delaying a pilot signal detected result 106 by a certain time, a comparison-discriminating circuit 2 can detect the discordance between signals of the currently used and a standby lines before the pilot signal detected result is sent from the receiving-end of the standby line after a faulty state of the currently used line is restored. Therefore, when switching back of a currently used line switching circuit, release of transmitting-end parallel, transmission of pilot signals through the standby line, and sending of the pilot signal detected result from the receiving-end of the standby line are performed after the currently used line is restored from the faulty state and a line switching system is returned to a normal state, the comparison-discriminating circuit 2 detects the discordance of signals between the two lines in advance. In other words, when the pilot signal detected result is sent from the receiving-end of the standby line, the circuit 2 does not hold the discriminated result of phase coincidence at the time of switching back.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a system backup type line switching device, and relates to a line switching device (-) that performs uninterrupted switching by comparing two special electric bits and phases.

[Conventional technology]

The third factor is an example of a configuration diagram of a (1+N) uninterrupted line switching system. The general switching sequence of the uninterrupted switching in FIG. 3 is as follows.

In other words, the presence or absence of a backup line failure is detected from the failure of the working line through the sending and receiving end line switching control circuits 18 and 19.
After confirming the usage status of the protection line, parallel operation at the sending end is performed. next.

Comparison of the faulty working line transmission signal 203 and protection line transmission signal 204 (both transmission signals 203 and 204 ζ: transmission signal 2011:, equivalent) at the receiving end (from -).

After the bit and signal phase are confirmed, switching (hitless switching) is performed, and repair of the faulty line is completed.

In addition, a simple cutback sequence is used to restore the working line from failure through the sending and receiving line switching control circuits 18 and 19.
Therefore, after comparing and confirming the bits and phases of the fault-recovered working line transmission signal 203 and the protection line transmission signal 204, a cutback (hitless switching) is performed. Next, the pilot signal is transmitted to the protection line by canceling the sending end parallelism.

A pilot signal is detected at the receiving end C2, and the switchback is completed. In other words, the 1-line switching system is in a normal state (-return).

FIG. 2 is a block diagram of the receiving end side of a conventional line switching system. The comparison/judgment circuit 2 compares the working line transmission signal 102 and the protection line transmission signal 101 (at the time of a working line failure, the transmission signals 101 and 102 are the same signal due to parallel transmission ends), pit by pit. and the protection line transmission signal 101 to determine if the bits and phases match.

The determination result 105 is output. Switching circuit 3 has judgment result 10
5 and the switching control signal 103, the working line transmission signal 1
02 and the protection line transmission signal 101 without momentary interruption, and outputs the working line signal 104. The pilot signal detection circuit 1 detects whether the protection line transmission signal 101 is a pilot signal and outputs a detection signal 106.

Here, the judgment result of the comparison judgment circuit 2 is required to have high accuracy in order to perform switching without bit errors (hitless switching). For example, in data communication, 1" in a data string.
Alternatively, if "0"s are continuous and only frame pulse data is transmitted, correct judgment results cannot be obtained with a short pit comparison monitoring time. Also.

In the above case, a correct determination result must be obtained even if the bit error rate deteriorates to about 110'.

Normally, in order to obtain correct judgment results, the bit comparison monitoring time is increased. Therefore, in the comparison/determination circuit, it takes a long time to determine whether the bits and phases of the signals between the working and protection lines match.

On the other hand, the pattern length of the signal used as the pilot signal only needs to be relatively short.

The pilot signal can be detected in a short time by the comparison/determination circuit 2.

[Problem that the invention attempts to solve]

The conventional line switching device described above is capable of recovering from faults in the working line.
From the second point, the switching circuit is switched back, the parallel transmission end is canceled, and the pilot signal is transmitted to the protection line, and the pilot signal is detected at the protection line receiving end.

It is determined that the next line switching is possible.

However, it takes longer for the comparison/judgment circuit to detect a signal mismatch between the working and protection lines than the pilot signal detection time, so when sending out the pilot signal detection results (:
In this case, the comparison/judgment circuit has not yet been able to detect a mismatch in the signals. Immediately after the fault was recovered, a fault occurred on the same working line.
When sending end paralleling is performed again, the comparison and judgment circuit determines that the bits and phases match at the time of switching back, even though the bits and phases of the signals between the working and protection lines do not actually match yet. Since it is held, one line switching will be performed. That is, line switching is performed when the bits and phases of signals between the working and protection lines do not match, so there is a drawback that errors occur during switching.

[Means for solving problems]

The line switching device of the present invention has N working lines #! A line switching system in which a backup line is provided for the C2 (at the receiving end C2), in the event of a failure of the working line.

means for determining whether bits and phases of signals between the working and protection lines match by comparing the working line signal and the protection line signal transmitted from the sending end parallel (-) on a pit-by-pit basis; means for switching the line without momentary interruption based on the determination result and the switching control signal; means for detecting a pilot signal transmitted on the protection line to confirm parallel operation at the transmitting end; and means for detecting the detection result of the pilot signal detecting means. and means for delaying the delay.

〔Example〕

Next, an embodiment of the present invention will be described with reference to FIG. Note that parts common to those in FIG. 2 are indicated by the same reference numerals.

Pilot signal detection circuit 1. The operation of the comparison/judgment circuit 2° switching circuit B is the same as that shown in FIG. The delay circuit 4 delays the pilot signal detection result 106 for a certain period of time and outputs a detection signal 107. In this embodiment, such a delay time is set t: after the failure of the working line is restored.

Before the pilot signal detection result is sent from the protection line receiving end, the comparison/judgment circuit 2 is configured to be able to detect signal mismatch between the working and protection lines. The switching circuit is switched back, the sending end is released from parallel, the pilot signal is transmitted to the protection line, and the pilot signal detection result is sent from the protection line receiving end.

When the line switching system returns to normal status (:ha.

The comparison/judgment circuit 2 detects a discrepancy in signals between the working and protection lines. That is, when the pilot signal detection result is sent from the protection line receiving end, the comparison and determination circuit 2 does not hold the determination result of phase matching at the time of cutback. This means that line switching is not performed until the bits and phases of the signals between the protection lines match. Therefore, according to the present invention, the same working line (= even in a situation where a failure occurs) immediately after recovery from a failure.

Switching without momentary interruption is possible.

〔Effect of the invention〕

The present invention described above delays the transmission of the pilot signal detection results, so that the nine-line switching system after failure recovery is able to perform the next switching sequence (:, before moving on), the comparison judgment circuit always Since it is possible to detect inconsistencies in the signals between the working and protection lines, even in situations where a failure occurs again on the same working line immediately after recovery from a failure, it is possible to prevent incorrect wiring before the pits and phases of the signals between the working and protection lines match. , there is no need to switch lines, and line switching can be done without interruption.

Margin below

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the receiving end side of a conventional line switching system, and FIG. 3 is a (1+
N) is a configuration diagram of an uninterrupted line switching system. DESCRIPTION OF SYMBOLS 1... Pilot signal detection circuit, 2... Comparison judgment circuit, 3... Switching circuit, 4... Delay circuit, 11...
Transmission end switching circuit, 12... Multiplexing circuit, 13... Line monitoring circuit, 14... Separation circuit, 15... Hitless switching circuit, 16... Pilot signal generation circuit, 17...
. . . Pilot signal detection circuit, 18 . . . Sending end circuit switching control circuit, 19 . . . Receiving end circuit switching control circuit. Figure 1

Claims (1)

[Claims] In a line switching system in which protection lines are provided for 1.N (≧1) working lines, when the working line fails, on the receiving end, the working line signal transmitted in parallel at the sending end and the protection line means for determining whether the bits and phases of the signals between the working and protection lines match by comparing the signals bit by bit; and switching the lines without momentary interruption based on the determination result of the determining means and the switching control signal. A line switching device comprising: means for detecting a pilot signal transmitted through a protection line in order to confirm parallel operation at a sending end; and means for delaying a detection result of the pilot signal detecting means.