JPH02260729A - Line switching system - Google Patents

Abstract

PURPOSE:To surely switch a line by using a fast digital private line itself by stopping the sending of a frame synchronization signal when detecting the fault of a transmission line in current use, and switching the line to a spare transmission line. CONSTITUTION:When the fault occurs in the line 9-2, a time division multiplexing device 1 detects frame step-out (REC), and switches the line setting of its own station to a spare line 14. and simultaneously, interrupts the sending of the frame synchronization signal by the violation of a CMI code rule to the line 9-1. A line terminating device 3 informs the detection of the frame step-out to a line terminating device 4 via the fast digital private line 7-1. The line terminating device 4 informs the occurrence of the frame step-out by a unit not ready(UNR) signal via the line 10-1. A time division multiplexing device 2 switches the line setting of its own device from the line 13 in current use to the spare line 14. In such a way, it is possible to switch both the time division multiplexing devices 1 and 2 to the spare lines synchronously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a line switching system for high-speed digital dedicated lines provided as working transmission lines and backup transmission lines.

(Prior Art) Conventionally, the following method has been adopted in order to synchronously switch between the opposite control device and the high-speed digital line when a line failure occurs on the high-speed digital dedicated line.

■A method of transmitting specific codes by temporarily using time slots allocated for users.

■A method that allocates time slots for control signal transmission to some of the time slots of high-speed digital leased lines, and provides dedicated bits for line switching instructions.

■A method in which a separate dedicated line is set up externally, and this line is used to transmit line switching instructions.

(Problem to be solved by the invention) The conventional method described above has the following drawbacks.

■In a method in which a specific code is transmitted by temporarily using a time slot allocated for a user, it may not be possible to distinguish between a user code and a specific code.

■If a dedicated bit is allocated to time slots for control signal transmission, the transmission efficiency will decrease.

■In a method in which an external dedicated line is provided to transmit line switching instructions, additional line charges are required, resulting in high costs.

The present invention has been made in view of these circumstances, and its purpose is to provide a line device that can reliably switch lines using the high-speed digital private line itself.

(Means for Solving the Problems) In order to achieve the above object, the line switching system of the present invention provides a first line termination device, a high-speed digital leased line, and a second line switching system.
A control device is provided at both ends of the active transmission and standby transmission, which are connected in series with the line termination device, and the transmission is performed between the control devices using the encoded inversion code, and the violation of the coded inversion code rule is prevented. In a transmission system in which frame synchronization is performed using a frame synchronization code, and the first and second line termination devices notify the control device of a unit not ready code when detecting frame synchronization loss, when a failure in the working transmission path is detected. Frame synchronization control means for stopping the transmission of a frame synchronization signal based on a violation of the coding inversion code rule on the working transmission line, and switching the working transmission line to the protection transmission line; upon receiving the unit not ready signal; and switching means for switching the working transmission line to the protection transmission line.

(Function) In the line switching system of the present invention, when the frame synchronization control means detects a fault in the current transmission path, it causes the current transmission path to stop transmitting a frame synchronization signal due to a violation of the encoding inversion code rule, and Switch the working transmission line to the backup transmission line. Further, when the switching means receives the unit not ready signal, the switching means switches the working transmission line to the backup transmission line.

(Example) Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. In the figure, 1.2 is a time division multiplexing device which is a control device, 3 to 6 are line termination devices, 7-i, 8-i (i=1.2> is a high-speed digital private line, 9-i to 12 -1 is a communication line 9-1, a line termination device 3, and a high-speed digital dedicated line 7-
1. Line termination device 4 and line 10-1 are working line 13
It consists of a line 11-i, a line termination device 5, a high-speed digital dedicated line 8-1, a line termination device 6, and a line 12-
1 constitutes the protection line 14. Both the working line 13 and the protection line 14 use code inversion (referred to as CMI) codes, and frame synchronization is achieved by frame synchronization signals based on violations of the CMI code rules.

Next, in the embodiment shown in FIG.
2 (transmission direction is from line termination device 3 to time division multiplexer 1)
Explains the operation when switching the line from the working port 1!13 to the protection line 14 when some kind of failure occurs.0
When line 9-2 becomes faulty, time division multiplexer 1 detects frame synchronization loss (REC), switches the line setting of its own station to protection line 14, and at the same time transmits CMI to line 9-1.
Transmission of the frame synchronization signal due to violation of the coding rule is stopped.

Therefore, the line terminating device 3 detects frame synchronization (RE).
C) will be detected. Then, the detection of frame synchronization is notified to the line termination device 4 via the high-speed digital private line 7-1.

The line terminating device 4 that received this notification is connected to the line 10-1.
A unit not ready (UNR) signal is used to notify that frame synchronization has occurred.

The time division multiplexer 2 that received this notification
3, and switches its own line setting from the working line 13 to the protection line 14. In this way, both time division multiplexers 1 and 2 can be switched in synchronization with the protection line 14.

In addition, when a failure occurs in the lines in the transmission direction from time division multiplexer 1 to time division multiplexer 2 (line 9-1, 10-1 and high-speed digital private line 7-1), the same procedure as described above occurs. The working line 13 is switched to the protection line 14.

(Effects of the Invention) As explained above, the line switching method of the present invention is
When a line fault occurs in a high-speed digital leased line, the control device that detects the fault stops sending frame synchronization signals to the line termination device on its own side due to a violation of the CMI coding rule. Then, the line terminating device on the own device side detects frame synchronization loss and notifies the other control device of the occurrence of frame asynchronization via the line terminating device on the other device side, so both control devices are synchronized. to switch from the working line to the protection line. Therefore, if the line switching method of the present invention is adopted, the line can be reliably switched to the opposite device without being affected by the user code, without deteriorating transmission efficiency, and without using the line externally. Can transmit instructions.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention. 1-2...Time division multiplexing device, 3-6...Line termination device, 7-1-8-i...High-speed digital line, 9-1
~12-1...Line, 13...Working line, 14...
・Backup line.

Claims (1)

[Scope of Claims] A control device is provided at both ends of a working transmission and a protection transmission in which a first line termination device, a high-speed digital dedicated line, and a second line termination device are connected in series, The transmission is performed using an encoded inverted code, and frame synchronization is achieved using a frame synchronization code due to a violation of the encoded inverted code rule, and when the first and second line termination devices detect frame synchronization, the control device In a transmission system that notifies a unit not ready code, when a fault in the working transmission line is detected, the transmission of a frame synchronization signal due to a violation of the encoding inversion code rule is stopped on the working transmission line, and the working transmission line is stopped. A line switching system comprising: frame synchronization control means for switching to the protection transmission line; and switching means for switching the working transmission line to the protection transmission line upon receiving the unit not ready signal.