JPH0738622A - Loopback circuit - Google Patents

Abstract

PURPOSE:To prevent a closed loop from being formed by loopback by allowing a loopback circuit for maintenance and monitoring of a transmission system to make normal loopback. CONSTITUTION:In order to operate a loop circuit 1 looping back a signal to a host device in the loopback circuit in each transmitter, a control circuit 3 is provided to the loopback circuit. The control circuit 3 compares the result of detection by an outgoing line side detection circuit 2 detecting an operation command signal commanding the signal loopback to the host side with the result of detection by an incoming line side detection circuit 4 to inhibit loopback when the operation command at the incoming line side is detected early.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loopback test circuit for testing or maintaining a transmission system. The present invention is
In particular, the present invention relates to a loopback control of a loopback circuit for test maintenance incorporated in a transmission device.

[0002]

2. Description of the Related Art FIG. 2 shows a folding circuit system incorporated in a conventional transmission device.

In this loopback system, a loop A circuit 1 loops back a communication signal to the high-order side at the low-order side input / output terminal, and a loop B circuit 5 loops back to the low-order side at the high-order side input / output terminal.
And the loop A circuit 1 in the communication signal from the upper side to the lower side
Loop A circuit 1 is operated by detecting the operation instruction signal of
Detection circuit 2 and loop B in the communication signal from lower to higher
A B detection circuit 6 for detecting the operation instruction signal of the circuit 2 and operating the loop B circuit 2 is provided.

Next, the operation of this configuration will be described.

When the loop A circuit 1 is operated and the communication signal is returned to the upper side, the operation instruction signal and the measurement signal of the loop A circuit 1 are sent as a return test signal for the communication signal from the upper side to the lower side. With this test signal, A
The detection circuit 2 detects the operation instruction signal of the loop A circuit 1 and operates the loop A circuit 1 according to the detection result. The loop A circuit 1 disconnects the lower side input / output according to the instruction of the A detection circuit 2 and returns the test signal from the upper side to the upper side.

Next, when the loop B circuit 5 is operated and the communication signal is returned to the lower side, the input direction of the test signal and the operation instruction signal of the loop A circuit 1 are applied to the loop B circuit 5.
Similarly, by changing to the operation instruction signal of B detection circuit 6
And the test signal from the lower order is folded back to the lower order by the loop B circuit 5.

FIG. 3 shows an example of the system configuration and shows a case where the device 10 and the device 20 are provided with folding circuits.

As a technique related to the formation of such a conventional folding test circuit, there is a technique disclosed in Japanese Patent Laid-Open No. 62-213349.

[0009]

In this conventional folding circuit system, the test access from the upper side is basically used. Therefore, if the test access point is moved to the lower side,
In the system configuration, a closed loop of folding is configured,
There was a problem that the normal maintenance could not be performed and the test maintenance function could not be exhibited.

For example, when the loopback in the upper direction is performed using the device 10 and the device 20 of FIG. 3 as a test access point, there is a problem that a closed loop is formed between the two devices 20.

The present invention solves such a problem, and an object of the present invention is to provide a loopback circuit which can realize a normal loopback function and can loop back from an arbitrary access point.

[0012]

According to the present invention, there is provided a first loop circuit for returning a communication signal to an upper side at a lower side input / output terminal, and a second loop circuit for returning a communication signal to a lower side at an upper side input / output terminal. In a loopback circuit of a transmission device having a loop circuit of, a first detection circuit for detecting the operation instruction signal of the first loop circuit in the communication signal from the upper side to the lower side,
A second detection circuit for detecting the operation instruction signal of the first loop circuit in the communication signal from the lower side to the higher side, the first detection circuit and the second detection circuit by the detection result of the second detection circuit. A control circuit that operates one loop circuit, and a third detection circuit that operates the second loop circuit by detecting an operation instruction signal of the second loop circuit in the communication signal from the lower side to the higher side. It is characterized by having and.

The control circuit preferably does not operate the first loop circuit when the operation instruction signal of the second detection circuit is detected earlier than the operation instruction signal of the first detection circuit.

[0014]

The control circuit for operating the loop circuit for returning the communication signal to the upper side at the lower input / output terminal of the transmission device includes the detection circuit for detecting the operation instruction signal of the loop circuit in the communication signal to the upper side and the lower circuit. The detection output of the detection circuit that detects the operation instruction signal of the loop circuit in the communication signal to the side does not perform loopback control when the detection by the communication signal to the upper side is early, and the detection by the communication signal to the lower side If the speed is fast, turn back control is performed.

Thus, the normal loopback function is realized, and the loopback test maintenance can be performed on any access point.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a folding circuit in a transmission apparatus according to an embodiment of the present invention. In the embodiment of the present invention, the loop A circuit 1 which is the first loop circuit for returning the communication signal to the upper side at the lower side input / output end, and the second loop circuit for returning the communication signal to the lower side at the upper side input / output end. In the loopback circuit of the transmission device including the loop B circuit 5 which is a loop circuit, the first feature of the present invention is that the operation instruction signal of the loop A circuit 1 in the communication signal from the upper side to the lower side is detected. An A detection circuit 2 which is a detection circuit, and an A detection circuit 4 which is a second detection circuit which detects the operation instruction signal of the loop A circuit 1 in the communication signal from the lower side to the higher side.
And a control circuit 3 for operating the first loop circuit according to the detection results of the first detection circuit and the second detection circuit.
And a third detection circuit B for operating the loop B circuit 5 by detecting the operation instruction signal of the loop B circuit which is the second loop circuit in the communication signal from the lower side to the upper side.
And a detection circuit 6.

Next, the folding operation in this embodiment will be described.

First, when the communication signal is returned to the lower side, the B detection circuit 6 detects the operation instruction signal of the loop B circuit 5 in the communication signal from the lower side, and the loop B circuit 5 is operated. The loop B circuit 5 disconnects the upper-side input / output according to the instruction of the B-detection circuit 6 and returns the communication signal to the upper side to the lower side.

Next, when returning the communication signal to the upper side,
The control circuit 3 controls the loopback operation of the loop A circuit 1 by comparing which of the two A detection circuits 2 and 4 detects the operation instruction signal of the loop A circuit 1 earlier. That is, when the detection of the operation instruction signal in the communication signal to the lower side by the A detection circuit 2 is faster than the detection of the operation instruction signal in the communication signal to the higher side by the A detection circuit 4, the control circuit 3 Activates the loop A circuit 1. If the A detection circuit 4 of the operation instruction signal in the communication signal to the upper side detects faster than the A detection circuit 2 of the operation instruction signal in the communication signal to the lower side, the control circuit 3 causes the loop A Do not operate circuit 1. The loop A circuit 1 receives the loopback instruction from the control circuit 3, disconnects the low-order side input / output, and loops back the communication signal to the low-order side to the high-order side.

For example, in the system configuration example of FIG.
When the left side device 10 is used as an access point for a loopback test in the upper direction, the right side device 20 is looped back when the loop operation instruction signal in the communication signal to the upper side is the loop operation instruction signal in the communication signal to the lower side. Wrapping is not performed because it is detected earlier. Therefore, a closed loop is not formed and a normal folding function can be realized.

[0022]

As described above, in the folding circuit of the present invention, in the folding circuit to the higher order side, the detection circuit for detecting the folding operation instruction signal in the communication signal of the above-mentioned direction is added to make the bidirectional circuit. Since the loop control loop circuit is operated by detecting the loopback operation instruction signal, a normal loopback function can be realized without loopback that forms a closed loop. As it can be folded back, the efficiency of test maintenance can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a folding circuit of a transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional folding circuit.

FIG. 3 is a diagram showing an example of a transmission system configuration.

[Explanation of symbols]

 1 loop A circuit 2, 4 A detection circuit 3 control circuit 5 loop B circuit 6 B detection circuit 10, 20 device

Claims (2)

[Claims] 1. A transmission comprising a first loop circuit for returning a communication signal to an upper side at a lower side input / output terminal, and a second loop circuit for returning a communication signal to a lower side at an upper side input / output terminal. In the loopback circuit of the device, a first detection circuit for detecting the operation instruction signal of the first loop circuit in the communication signal from the upper side to the lower side, and the first detection circuit in the communication signal from the lower side to the higher side. A second detection circuit that detects an operation instruction signal of one loop circuit; a control circuit that operates the first loop circuit according to the detection results of the first detection circuit and the second detection circuit; And a third detection circuit for operating the second loop circuit by detecting the operation instruction signal of the second loop circuit in the communication signal from the above to the upper side. 2. The control circuit does not operate the first loop circuit when the detection of the operation instruction signal of the second detection circuit is faster than the detection of the operation instruction signal of the first detection circuit.
Folded circuit described.