JPH0336832A - Transmission line changeover system - Google Patents

Abstract

PURPOSE:To switch a transmission line automatically without causing out of frame synchronization by providing a synchronizing circuit and a fault detection circuit for clock interrupt of a transmission line, a CRC error and out of frame synchronization to a reception section of each transmission line. CONSTITUTION:A clock is extracted by synchronizing circuits 9,12 after B/U conversion as to each of systems 0, 1, frame synchronization is applied and a fault is detected by transmission line fault detection circuits 10, 13. Then fault information is informed to a fault display section 4 and information such as clock interrupt of a transmission line, a CRC error and out of frame synchronization is informed to a transmission line switching control circuit 16. The data of the systems 0, 1 is selected by a transmission line switching selector 14 and the data is outputted in the timing in matching with the transmission line terminator 1 with a frame phase correction circuit 15. The circuit 16 decides the system switching through the receipt of each information when there is not fault in the transmission line of the system not in use and there is a fault in the transmission line of the system in operation and outputs the switching signal to the selector 14 to switch the transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission line switching system, and particularly to a transmission line switching system in a redundant transmission line.

[Conventional technology]

A conventional transmission path switching system of this type will be explained using FIG. 2.

Directional and
Transmission lines are provided for each system, and system switching of the transmission lines is performed in each direction by a transmission line termination device on the side corresponding to the receiving section. At this time, since the switching method is the same regardless of the direction, the explanation will focus on one direction.

The data output from the frame synchronization signal insertion circuit (SYNC) 38 of the transmitter 24 of the transmission line termination device 21 of the opposite station is transmitted to the U/B conversion circuit (U/B> 39 of the 0 system and the U/B converter circuit (U/B) 39 of the 1 system).
The /B conversion circuit (U/B) 40 converts the signal into a bipolar signal and transmits it to the O system transmission line 25 and the 1 system transmission line 26, respectively.
The signal is then input to the 0-system B/U conversion circuit (B/U) 27 and the 1-system B/U conversion circuit (B/U) 30 of the reception unit 22 of the transmission line termination device 20 of the local station. B/U conversion conversion unit synchronization circuit (BSYNC) for each of O system and 1 system
28 (31) extracts the clock, clock disconnection detection circuit (CAD) 29 (32) detects a clock disconnection failure, and connects the failure display unit 23 and transmission path switching control circuit (CT).
L) Notify 37 of clock disconnection. Transmission line termination device 2
The O system and 1 system data from 1 are selected by a transmission path switching selector (SEL) 33 at the subsequent stage. A frame synchronization circuit (FSYN) is provided after the transmission path switching selector 33.
C) 34 and a frame phase correction circuit (F/A) 35, which outputs data at a timing suitable for the transmission line termination device 20. Transmission path failure detection circuit (ALM-DEC)
36 monitors the fault in the transmission path of the used system, and displays the fault display section 2.
At the same time, the fault information is output to the transmission path control circuit 37.
y check) Notifies errors and frame synchronization loss.

The transmission line switching control circuit 37 re-determines the occurrence of a failure based on the reception of the clock disconnection of the polyline, the CRC error of the used system, and the out of frame synchronization, and determines that there is no failure on the unused transmission line and that there is no failure on the used transmission line. When there is a problem, system switching is determined and a switching signal is output to the transmission path switching selector 33, thereby switching the transmission path.

[Problem that the invention seeks to solve]

The conventional transmission line switching method described above obtains failure information by only detecting clock disconnections on unused transmission lines, so CRC errors and frame synchronization due to deterioration and interference of the transmission line are detected. If failure information is not detected and a CRC error or frame synchronization is detected even after system switching, the system will be switched again, resulting in continuous system switching. There is a drawback that it takes time to re-establish frame synchronization due to errors in transmission delays between the first and first systems.

[Means for solving problems]

The transmission line switching system of the present invention switches between the first and second transmission lines, which are mutually arranged as redundant systems.
In a transmission line switching method performed by a transmission line switching selector provided in a receiving unit of a transmission line terminating device that terminates both ends of a transmission line, the transmission line is transmitted to the receiving unit of the transmission line terminating device via the second transmission line. a first synchronization circuit that performs clock synchronization and frame synchronization with the signal transmitted by the signal; a first failure detection circuit that detects clock disconnection and frame synchronization in the first synchronization circuit; a second synchronization circuit that performs clock synchronization and frame synchronization with the signal, a second failure detection circuit that detects clock disconnection and frame synchronization in the second synchronization circuit, and the first and second failure detection circuits. and a transmission path switching control circuit that controls switching of the transmission path switching selector based on the fault information output by the transmission path switching control circuit.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

Directional and
Transmission lines are provided for each system, and system switching of the transmission lines is performed in each direction by a transmission line termination device on the side corresponding to the receiving section. At this time, since the switching method is the same regardless of the direction, the explanation will focus on one direction.

The data output from the frame synchronization signal insertion circuit (SYNC) 17 of the transmission section 5 of the transmission line termination device 2 of the opposing station is transmitted to the U/B conversion circuit (U/B) 18 of the 0 system and the U of the 1 system.
/B conversion circuit (U/B') ↑ is converted into a bipolar signal and transmitted, respectively to the O system transmission 16 and the 1 system transmission line 7.
B of the 0 system of the receiving section 3 of the transmission path termination device 1 of the local station.
/U conversion circuit (B/U) 8 and 1 system B/U conversion circuit (
B/U) 11. For each of the O system and 1 system, clock extraction and frame synchronization are performed using the B/U conversion period circuit (SYNC) 9 (12), and a failure is detected at the transmission path fault detection circuit (ALM-DEC) io (13:). Detection is performed, fault information is displayed on the fault display section 4, and the clock is cut off on the transmission path switching circuit (CTL circuit 16).

Notifies of CRC error and frame synchronization loss.

The O-system and 1-system data from the transmission line termination device is selected by the transmission line switching selector (SEL) 14 at the subsequent stage, and sent to the transmission line termination by the frame phase correction circuit (F/A) 15 at the subsequent stage. Output data at a timing that suits the device ■.

The transmission line switching control circuit 16 has many clocks cut off.

When a CRC error or frame synchronization is received and there is no fault in the transmission line of an unused system and there is a fault in the transmission line of the used system, system switching is determined and a switching signal is output to the transmission line switching selector 14. By doing this, the transmission path is switched.

〔Effect of the invention〕

As explained above, the present invention provides a synchronization circuit in the receiving section of each transmission line of the 0 system and 1 system, and a clock disconnection of the transmission line and a CRC.
By installing a failure detection circuit for errors and out-of-frame synchronization, it is possible to automatically switch transmission paths without causing out-of-frame out-of-frame synchronization. Since the condition of the road can be monitored, there is an effect that continuous switching of the system does not occur.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional transmission line switching system. 1.2... Transmission line termination device, 3... Receiving section, 6...
・0 system transmission line, 7...1 system transmission line, 9.12...synchronous circuit, 10.13...transmission line failure detection circuit, 14.
... Transmission path switching selector, 16... Transmission path switching control circuit.

Claims (1)

[Scope of Claims] A transmission line provided in a receiving section of a transmission line terminating device for terminating both ends of the first and second transmission lines for switching between the first and second transmission lines, which are mutually arranged as a redundant system. In the transmission line switching method performed by a switching selector, the receiving section of the transmission line terminating device includes a first synchronization circuit that performs clock synchronization and frame synchronization with the signal transmitted through the first transmission line; The first circuit detects clock interruption and frame synchronization in the synchronization circuit of
a second synchronization circuit that performs clock synchronization and frame synchronization with the signal transmitted by the second transmission path; and a second synchronization circuit that detects clock disconnection and frame synchronization in the second synchronization circuit. A transmission line switching system comprising: a failure detection circuit; and a transmission line switching control circuit that controls switching of the transmission line switching selector based on failure information output by the first and second failure detection circuits.