JPS6339256A - Channel d loop back system - Google Patents

Abstract

PURPOSE:To allow a terminal side to judge whether communication is feasible by outputting a channel E bit different from the channel D bit of each terminal from a network side when a D channel NT loop back instruction Loop D=1 is given. CONSTITUTION:A selection signal output part 13 is provided with a selector 21 and an inverter 22. Similar to selectors 11 and 12, the selector 21 outputs the signal of a terminal to a terminal Y with loop D=0 given, and outputs the signal of a terminal B with loop D=1 given. When no D channel NT loop back test is conducted, the channel D from the terminal is folded to a channel E through the terminal Y form the terminal A of the selector 21, and therefore the terminal judges that communication is feasible. When the D channel NT loop back test is conducted, the inverter 22 and the selector 21 fold the inversion signal of the channel D to the channel E, and therefore the terminal stops channel D communication.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Prior Art (Figures 4 to 6) Problems to be Solved by the Invention Means for Solving the Problems (Figure 1) Effects Embodiment (FIGS. 2 and 3) Effects of the invention [Summary] The present invention provides a method for testing the network termination device in a network termination device NT that connects a network in an 15DN or INS with a plurality of terminals TE. Even if an access request is made from the terminal during a D channel loopback test from the side, the received D channel signal and another signal are looped back to the terminal via the E channel, so that the terminal cannot access it. .

[Industrial application field]

The present invention is a comprehensive service digital Q'f4 (In t
era ted 5 services Digital
Network; ISDN) or advanced information and communication system (Information Network)
This is related to the D channel loopback method in a network termination device that connects a network and multiple terminals in, for example, the network terminating device. The present invention relates to a device in which, even when an access request is made to a network termination device, the network termination device returns a signal to the terminal via the E channel to inform the terminal that the network termination device is in use.

[Conventional technology]

As shown in FIG. 4, the 15DN and the like are provided with a subscriber line 100 and a network termination device 101 for connecting a digital switching network and a plurality of terminals TE+-TE1-TEn in a home. This network termination device 101 is connected to a subscriber line and terminates the network, and inside the home of the network termination device 101, there are a plurality of terminals TE, TE, ...
TEn is connected.

Data having a frame structure as shown in FIG. 5 is transmitted on this bus. FIG. 5(a) shows a frame transmitted from the network terminal device 101 to the terminals TE to TEn,
FIG. 5(b) shows the network terminal device 10 from the terminals TE+ to TEn.
This is the frame transmitted in 1st frame.

Here, F is a frame bit indicating a frame separation, L is a DC balance bit, D is a D channel bit indicating signal data, and E is a D channel bit indicating permission for use to prevent contention. Fa is the auxiliary frame bit, B1 is the 81 channel bit indicating a channel for audio or other information, and B2 is the B2 channel bit indicating a channel for audio or other information. be. Descriptions of other bits will be omitted for the sake of brevity.

In the home, multiple terminals TE1 to T are connected to the network terminal device 101.
Since En is connected, there is a possibility that multiple terminals can access it at the same time. In order to avoid this contention, the D channel bit of the user network U/N, that is, the home bus, is set to
Wrapping back to channel bits. The terminal that requested access compares the received E channel bits in FIG. It is possible to determine that the user has the right to use the device and perform communication according to a predetermined procedure. However, when the transmitting D channel and the receiving E channel are compared and they do not match, it is recognized that the terminal is in competition with another terminal and is not permitted to use the terminal, and stops communication on the D channel.

From the network side, for example, when a network termination device is installed or for maintenance purposes, the wiring condition is checked. In this case, a network termination device loopback test is performed as shown by the dotted line in FIG. 4.

That is, channels B1, B2, and D can be looped back independently according to a command from the network.

The network sends a return command to the subscriber line 10 by checking whether the transmitted signal and the received signal match.
0 or the network terminal device 101.

Note that the network terminal device 101 receives LOOPD% B 1, B2 from the digital signal transmitted from the subscriber line 100.
A means for extracting such information is provided.

[Problem that the invention seeks to solve]

As shown in FIG. 6, the network termination device 101 is provided with selectors 111 and 112 in order to perform the loopback test as described above. It is configured so that the signal at terminal B is output from terminal Y when the NT return command is output. Therefore, the selector 111 is as described above.

When opD is "0", the upstream D channel is passed through,
When LoopD = r l J, the D channel is looped back to the network side. Also, the selector 112 is as described above.

When opD=rOJ, the downlink D channel is passed through,
When LoopD = r I J, the downlink D channel is set to all "1s", that is, to a non-communication state. This is to prevent meaningless signals from being sent to the terminal side during the D channel NT loopback test. Also, bus side E in the house.
The channel is the same as the D channel.

By the way, when the network side is performing such a loopback test, when the terminal side makes an access, the assignment of the D channel is done in the same way when the D channel is looped back, so the terminal is assigned the B channel NT in the D channel communication.
If you know that a return exam is in progress, do not access the site. However, D
During the channel loopback test, the D channel from the terminal is looped back to the E channel, so although it is recognized that communication is possible, in reality, the selector 111.1
12, there is a problem that the D channel cannot communicate with the network side.

An object of the present invention is to improve such problems and, when performing a D channel NT return test from the network side, to transmit a different signal to the terminal side without transmitting the received D channel in full E channel. The present invention provides a D-channel folding method.

Means for Solving Problem c] In order to achieve the above object, in the present invention, as shown in FIG. 1, a selection signal output section 13 is provided in the network termination device 1 in addition to the selectors 11 and 12. This selection signal output section 13 receives a D channel return command LoopD =
When r I J, even if there is an access request from the terminal, the E channel bits with a different pattern from the D channel bits are output, and when LoopD = r OJ, when there is an access request from the terminal, the E channel bits are output It operates to wrap channel bits back to E channel bits.

[Effect]

D channel NT return command Loo from the network side
When pD = r I J, the selection signal output section 13 outputs an E channel bit that is different from the D channel bit of each terminal, so the network side performs a D channel return test on the network termination device 1. Even if an access request is made from a terminal at home, the returned E channel bit will be used as the D channel bit of any terminal.
Since the bits do not match, the terminal that made the access request assumes that there is a conflict with another terminal and performs the process, thereby resolving the above-mentioned problem.

Of course, if there is no test from the network side, Loop
D = r OJ, then the selection signal output section 13
Since the D channel bits from the terminal are returned as E channel bits, the terminal side can use this to determine whether communication is possible. Note that the selectors 11 and 12 each perform the same operation as the selectors 111 and 112 in FIG. 6 described above.

〔Example〕

An embodiment of the present invention will be described based on FIG. 2 with reference to a map.

In FIG. 2, a network termination device 1 corresponds to the network termination device 101 shown in FIG. 4, and is connected to the network via a subscriber line, and is connected to a plurality of terminals inside the home. It has a function to extract signals such as Loop D.

1112 is a selector, which corresponds to selector 111 and 112 in FIG.
When LoopD is rOJ, selectors 11 and 12 output the signal at terminal A from terminal Y, and when LoopD is rlJ, the selectors 11 and 12 output the signal at terminal B.

The selection signal output section 13 includes a selector 21 and an inverter 22.
The selector 21 is equipped with the selector 11.1.
Similarly to 2, when Loop D is "0", the signal of terminal A is output to terminal Y, and when Loop D is "1", the signal of terminal B is output.
Outputs the signal.

When the D channel NT return command LoopD = r I J is being applied from the network to perform a test, the selector 11 transfers the downlink D channel applied to the terminal to the network side, as in the case of Fig. 6. In return, the selector 12 outputs all "1"s applied to the terminal B to enter a non-communication state. Also LoopD
= r OJ, the selector 11 outputs the D channel applied to the terminal A through-through, and outputs the upstream D-channel sent from the terminal of the user network through-output. And in the selector 12, LoopD = r O
When J, the upstream D channel applied to terminal A is passed through.

By the way, in the selector 21, the path side reception D channel is input as is to the terminal A, and the inverter 22 is input to the terminal B.
The inverted signal of the receiving D channel on the lotus side is inputted through the channel. And like selector 11.12, Loop
When D = r I J, the signal from the terminal B is output to the glass Y signal, and when LoopD r OJ, the signal from the terminal A is output to the terminal Y, which becomes the E channel.

That is, when the D channel NT loopback test is not performed, LoopD-r OJ is established, and the D channel from the terminal is looped back to the E channel from terminal A of the selector 21 via terminal Y, so the terminal When the same signal is returned, it is determined that communication is possible.

By the way, when the D channel NT loopback test is conducted,
In other words, if LoopD = r I J, then 1-, the inverted signal of the D channel received by the selection signal output section 13 by the inverter 22 and selector 21 is returned to the channel, so the terminal will compete with other terminals. D channel communication is stopped.

Even when there is no communication, that is, reception D channel is “1”, Lo
When opD = r I J, rOJ, which is an inverted signal of the D channel, is returned to the E channel, so the terminal thinks that another terminal is communicating, and
Don't access channels.

Another embodiment of the present invention will be described based on FIG. Third
The figure shows another example of the configuration of the pseudo display signal output section. Third
In the example shown in the figure, the terminal B of the selector 21 has "
All "0"s are applied by the "0" output section. As a result, the same effect as in the case of FIG. 2 can be obtained.

However, if the terminal in use is communicating, the user network's D
When outputting to the channel for a long period of time, in the embodiment shown in FIG. 2, the terminal can immediately determine the collision, and thus stops communication on the D channel, but in the embodiment shown in FIG. 3, the terminal maintains the communication state and outputs "1" By outputting ``0'' and receiving ``0'', it is determined that there is a collision, and D channel communication is stopped for the first time. However, the signal length of the D channel is determined and "1" is output during that time, so there is no problem.

〔Effect of the invention〕

According to the invention, the D channel NT from the network
During the loopback test, a signal different from that of the D channel is sent to the E channel on the bus to the terminal, so
The terminal recognizes that the D channel is in use and does not access the D channel. Therefore, a lean system can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention; FIG. 2 is a configuration diagram of one embodiment of the invention; FIG. 3 is a diagram illustrating another embodiment of the invention; FIG. 4 is a system configuration diagram for a network termination device; FIG. 5 is a frame configuration diagram at the user/network interface, and FIG. 6 is an explanatory diagram of a conventional network termination device. 1.-Network termination device 11.12-Selector 13--Selection signal output section 21--Selector 22--Inverter

Claims (1)

[Claims] By the D channel loopback command (LoopD), the upstream D
In the D channel loopback method, which includes a selector means for selecting whether to pass through the channel or loop back the channel, and a selector means for selecting whether to pass the downstream D channel or to put it in a no-signal state, the upstream bus side D A selection signal output means (13) is provided to select whether to loop back the channel or to output a different signal indicating that communication is in progress, and during the D channel loopback test, a signal indicating that communication is in progress is output to the E channel, and the terminal TE switches to the D channel. D channel loopback method that prevents access.