JPH04258027A - Duplex transmission line changeover system - Google Patents

Abstract

PURPOSE:To allow a terminal equipment and a network to select a same line at all times in a terminal block duplicate service of a high speed digital line. CONSTITUTION:A terminal equipment A inserts an index signal to a signal sent to a standby line. When a trouble takes place in a terminal equipment block of the terminal equipment A side and only the network selects the active system, a terminal equipment B detects an index signal and a switching signal is inserted to a transmission signal to the terminal equipment A. When the terminal equipment A detects the switching signal, the terminal equipment A allows a transmission circuit and a reception circuit to execute the changeover of the active line and the standby line and the network selects the active line.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a transmission line switching system,
In particular, it relates to a switching system for duplex transmission lines between terminal sections.

0002

2. Description of the Related Art A method of duplicating terminal sections is known as one of the methods for improving the reliability of a transmission line. Among these duplex systems, a system is known in which the terminal side and the network side monitor their respective received signals, and when a failure is detected, each system independently switches the operating system.

FIG. 2 shows a conventional configuration of such a duplex transmission line switching system. In the illustrated duplex transmission line switching system,
The terminal section on the terminal device A side and the terminal section on the terminal device B side are duplicated. Each of the terminal devices A and B includes a 0-system line interface circuit 101, a 1-system line interface circuit 102, and a selection circuit 202. A selection circuit 201 is provided within the network.

[0004] The 0-system line interface circuit 101 sends out a transmission signal to the 0-system line, and passes the received signal received from the 0-system line to the selection circuit 202 . Similarly, the 1-system line interface circuit 102 sends a transmission signal to the 1-system line, and passes the received signal received from the 1-system line to the selection circuit 202. The selection circuit 202 selects the received signal received from the 0-system line interface circuit 101 and the 1-system line interface circuit 10.
Select one of the received signals received from 2. On the other hand, a selection circuit 201 in the network selects either the transmission signal via the 0-system line or the transmission signal via the 1-system line in the terminal section and passes it to the relay section.

Referring to FIG. 2, the operation when transmitting data DA from terminal device A to terminal device B will be explained. First, the transmission data DA is supplied to the 0-system line interface circuit 101 and the 1-system line interface circuit 102 of the terminal device A, and is sent to the 0-system line and the 1-system line, respectively. Next, the selection circuit 201 in the network selects data DA via the 0-system line in the terminal section and data D via the 1-system line.
Select one of A and pass it to the relay section. The relay section passes the data DA to both the 0-system line and the 1-system line of the terminal section on the terminal device B side. In terminal device B, data DA via the 0-system line is received by the 0-system line interface circuit 101 and passed to the selection circuit 202, and data DA via the 1-system line is received by the 1-system line interface circuit 102. and passes it to the selection circuit 202. Selection circuit 20
2 selects either the data DA received from the 0-system line interface circuit 101 or the data DA received from the 1-system line interface circuit 102. The operation when transmitting data DB from terminal device B to terminal device A is also similar to the above.

[0006]

By the way, in the conventional duplex transmission line switching system described above, the selection circuit 202 in the terminal device and the selection circuit 201 in the network perform switching operations independently. Therefore, the transmitted signal and the received signal may pass through different lines. Therefore, there is a problem that the terminal device cannot recognize this.

An object of the present invention is to provide a duplex transmission line switching system that can always match the line selected by the selection circuit in the network with the line selected by the terminal device.

[0008]

[Means for Solving the Problems] The duplex transmission line switching system according to the present invention is a duplex transmission line system in which only the terminal section is duplexed, and the switching operation within the network and the switching operation of the terminal equipment are performed independently. In a transmission line switching system of a terminal device, means for inserting an indicator signal indicating that the signal is transmitted via the protection line into a transmission signal sent to a protection line, and means for detecting the indicator signal from a received signal; means for inserting a switching signal into a transmission signal sent to a working line and a protection line when the indicator signal is detected; means for detecting the switching signal from the received signal; and when detecting the switching signal;
It has means for switching between a working system and a protection system of the transmission line.

[0009]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a duplex transmission line switching system according to an embodiment of the present invention. In this embodiment, the terminal section on the terminal device A side and the terminal section on the terminal device B side are duplicated. Each of the terminal device A and the terminal device B includes a 0-system line interface circuit 101, a 1-system line interface circuit 102,
In addition to the selection circuit 202, the selection circuits 203 and 204
, index signal insertion circuit 301, switching signal insertion circuit 302,
It has an index signal detection circuit 401, a switching signal detection circuit 402, and a switching circuit 501.

The indicator signal insertion circuit 301 inserts into the transmission signal an indicator signal S indicating that the signal is via the protection line, and passes the inserted signal to the selection circuits 203 and 204. Selection circuit 204
selects the transmission signal received from the switching signal insertion circuit 302 when the 0 system line is the working line, and selects the transmission signal received from the index signal insertion circuit 301 when the 0 system line is the protection line. , and is passed to the 0-system line interface circuit 101. The selection circuit 203 selects the transmission signal received from the switching signal insertion circuit 302 when the 1st line is a working line, and selects the transmission signal received from the index signal insertion circuit 301 when the 1st line is a protection line. It is selected and passed to the 1-system line interface circuit 102. The 0-system line interface circuit 101 sends the transmission signal received from the selection circuit 204 to the 0-system line, and passes the reception signal received from the 0-system line to the selection circuit 202. The 1-system line interface circuit 102 sends the transmission signal received from the selection circuit 203 to the 1-system line, and passes the reception signal received from the 1-system line to the selection circuit 202. The selection circuit 202 selects the received signal received from the 0-system line interface circuit 101 when the 0-system line is the working line, and selects the received signal received from the 1-system line interface circuit 102 when the 1-system line is the working line.
The received signal received from is selected and passed to the switching signal detection circuit 402. The switching signal detection circuit 402 is the selection circuit 20
A switching signal C is detected from the received signal selected in step 2. The index signal detection circuit 401 detects the index signal S from the received signal selected by the selection circuit 202. When the index signal detection circuit 401 detects an index signal, the switching signal insertion circuit 302 inserts the switching signal C into the transmission signal and passes it to the index signal insertion circuit 301 and the selection circuits 203 and 204. When the switching signal detection circuit 402 detects a switching signal, the switching circuit 501 selects selections 202, 203, and 204.
to switch between the working line and the protection line.

[0011] The operation when the 0-system line on both the terminal device A side and the terminal device B side is the working line will be described below. First, transmission data DA sent from terminal device A to terminal device B is supplied to switching signal insertion circuit 302. The switching signal insertion circuit 302 includes the index signal detection circuit 40
Since no index signal was detected in step 1, the transmitted data D
Transmission data DA without inserting switching signal C into A
The index signal insertion circuit 301 and selection circuits 203 and 204
pass it on to The index signal insertion circuit 301 inserts the transmission data DA
An index signal S is inserted into the input signal S, and it is passed to the selection circuit 203 and the selection circuit 204 as a transmission signal DA+S. The selection circuit 204 selects the transmission signal DA received from the switching signal insertion circuit 302 and sends it to the 0-system line interface circuit 101.
pass it on to The selection circuit 203 selects the transmission signal DA+S received from the index signal insertion circuit 301 and passes it to the 1-system line interface circuit 102.

Next, a selection circuit 201 in the network selects the transmission signal DA via the 0-system line in the terminal section and passes it to the relay section. The relay section passes the transmission signal DA to both the 0-system line and the 1-system line of the terminal section on the terminal device B side.

In the terminal device B, the received signal DA via the 0-system line is received by the 0-system line interface circuit 101 and passed to the selection circuit 202, and the received signal DA via the 1-system line is sent to the 1-system line. It is received by the interface circuit 102 and passed to the selection circuit 202. The selection circuit 202 receives the received signal D from the 0-system line interface circuit 101.
A is selected and passed to the switching signal detection circuit 402 and the index signal detection circuit 401. Since the switching signal detection circuit 402 does not detect the switching signal C from the received signal DA, the switching circuit 50
1 does not instruct the selection circuits 202, 203, and 204 to switch. Since the index signal detection circuit 401 also does not detect the index signal S from the received signal DA, the switching signal insertion circuit 302 does not insert the switching signal C into the transmission data DB. The same applies when transmitting data DB from terminal device B to terminal device A.

Now, suppose that a failure occurs in the 0-system line on the terminal device A side. Assume that the terminal device A is unable to detect this fault, and only the network side detects it and switches the active system from the 0 system line to the 1 system line. A selection circuit 201 in the network selects the transmission signal DA+S via the 1-system line and passes it to the trunk line.

In the terminal device B, the reception signal DA+S received by the 0-system line interface circuit 101 is passed to the index signal detection circuit 401. Index signal detection circuit 40
1 detects the index signal S. Therefore, the switching signal insertion circuit 302 inserts the switching signal C into the transmission data DB. This transmission signal DB +C is sent to the terminal device A via the selection circuit 203, the 0-system line interface circuit 101, and the selection circuit 201 in the network.

In the terminal device A, the received signal DB+C received by the 0-system line interface circuit 101 is passed to the switching signal detection circuit 402. Switching signal detection circuit 40
2 detects the switching signal C. Therefore, the switching circuit 501 instructs the selection circuits 202, 203, and 204 to switch between the active system and the standby system. The selection circuit 204 selects the transmission signal DA+S from the index signal insertion circuit 301 and passes it to the 0-system line interface circuit 101. The 0-system line interface circuit 101 sends out a transmission signal DA+S to the 0-system line. The selection circuit 203 is the switching signal insertion circuit 3
02 is selected and passed to the 1-system line interface circuit 102. The 1-system line interface circuit 102 sends out a transmission signal DA to the 1-system line.

As a result, terminal device B receives the reception signal DA. Since the index signal detection circuit 401 does not detect the index signal, the switching signal insertion circuit 302 stops inserting the switching signal C into the transmission data DB.

[0018]

As explained above, the present invention provides a means for inserting, in a transmission circuit of a terminal device, an indicator signal indicating that the signal is sent via the protection line into a transmission signal sent to the protection line;
means for transmitting a switching signal to an opposing terminal device when an index signal is detected from a received signal; a means for detecting an index signal and a means for detecting a switching signal are provided in a receiving circuit of the terminal device; By providing means for instructing the transmitting circuit and receiving circuit to switch between the working line and the protection line when a signal is received, the line selected by the selection circuit in the network and the line selected by the terminal device are always switched. It can be matched.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a duplex transmission line switching system according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional duplex transmission line switching system.

[Explanation of symbols]

101 0 system line interface circuit 102 1 system line interface circuit 201 Selection circuit 202 Selection circuit 203 Selection circuit 204 Selection circuit 301 Index signal insertion circuit 302 Switching signal insertion circuit 401 Index signal detection circuit 402 Switching signal detection circuit 501 Switching circuit

Claims (2)

[Claims] [Claim 1] In a transmission line switching system for terminal equipment in a transmission line redundancy system in which only the terminal section is duplexed and the switching operation within the network and the switching operation of the terminal equipment are performed independently, means for inserting into a transmission signal to be sent an indicator signal indicating that the signal is via the protection line; means for detecting the indicator signal from the received signal; and upon detecting the indicator signal, the signal is transmitted to the working line and the protection line. means for inserting a switching signal into a transmitted signal, means for detecting the switching signal from the received signal, and means for switching between a working system and a standby system of the transmission line when the switching signal is detected. A redundant transmission line switching method. 2. In a transmission line switching method for a terminal device in a transmission line duplexing method in which only the terminal section is duplexed and the switching operation within the network and the switching operation of the terminal device are performed independently, the terminal device The transmitting circuit includes a means for inserting an indicator signal into the transmission signal to be sent to the protection line to indicate that the signal is transmitted via the protection line, and a means for inserting a switching signal to the opposing terminal device when the indicator signal is detected from the received signal. the receiving circuit of the terminal device has a means for detecting the index signal and a means for detecting the switching signal, and upon receiving the switching signal, the receiving circuit of the terminal device 1. A duplex transmission line switching system comprising means for instructing a user to switch between a working line and a protection line.