JPS639706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic return loop creation circuit, and particularly to an automatic return loop creation circuit for a subscriber line in a communication network that forms a return loop at one end and measures transmission quality.

In order for a communication network to provide high-quality communication services to its accommodated subscribers, it is necessary to constantly measure and monitor the transmission quality of communication network subscriber lines and to perform preventive maintenance to prevent deterioration of the transmission quality within the network. .

FIG. 1 is a diagram showing an example of a conventional intra-network transmission quality measurement and monitoring system in a data exchange network. 1st
In the figure, to measure the transmission quality of a subscriber line L1 that connects a terminal device T1 accommodated in a data exchange network N to a data exchange SW1, the subscriber line L1 is connected back at a terminal device TE1, and then at the data exchange SW1. Connecting the error rate measuring device M1 and transmitting a measurement signal to the subscriber line L1, and comparing the signal sent back from the terminal device TE1 with the measurement signal received and transmitted by the error rate measuring device M1. Implemented by According to such a measurement method, the data communication service to the terminal device T1 must be interrupted during the measurement period, causing inconvenience to the subscribers of the data exchange network N. Furthermore, it requires labor to reconnect the subscriber line L1 at the terminal device TE1 every time a measurement is made. Therefore, it is difficult to constantly measure and monitor the transmission quality of subscriber lines within the data exchange network using such measurement methods. The following measurement and monitoring method has been proposed as a countermeasure for the above-mentioned drawbacks. That is, in FIG. 1, the data exchanger SW2
constantly monitors the communication status of the accommodated terminal device T2, and connects the subscriber line L2 to the terminal device T2 that is in a non-communicating state.
is connected to the measurement unit M2, and a signal is sent to the termination device TE2 of the subscriber line L2 to create a return loop for the subscriber line L2, and after the subscriber line L2 is in a loop state, transmitter S
A measurement signal is sent to the subscriber line L2 from the terminating device TE2, and the signal sent back is received by the receiver R in the measurement unit M2 and compared with the transmitted measurement signal to detect errors in the subscriber line L2. rate becomes measurable. When a call to the terminal device T2 occurs during measurement monitoring, the data exchange SW2 detects the call, immediately interrupts the measurement, and processes the call. After the end of the call, the data exchange resumes the measurements again. According to this transmission quality measurement and monitoring method, the transmission quality of the subscriber line L2 within the data exchange network N can be constantly measured and monitored without impairing the communication service to the subscribers, thereby preventing deterioration of the transmission quality within the network. It becomes possible to perform maintenance.
However, in this transmission quality measurement and monitoring method, the terminal equipment
A signal for creating a return loop at TE2 is sent from data exchange SW2 to subscriber line L2.
It is necessary to transmit via the subscriber line L2.
This will place restrictions on the signal system used for this purpose.

The purpose of this invention is to eliminate the above-mentioned drawbacks of conventional in-network transmission quality measurement and monitoring methods, and to enable constant measurement and monitoring of subscriber line transmission quality without affecting the signal system used in subscriber lines. The goal is to realize a circuit that automatically creates a return loop.

According to the present invention, this purpose is to provide a non-communication state detection circuit which is provided in the subscriber line between the terminal device and the exchange and detects a non-communication state on the exchange side and the terminal device side, and a communication state between the exchange side and the terminal device side. It has a communication request signal detection circuit that detects each request signal, and when both no-communication state detection circuits detect a no-communication state, a return loop is formed in the selection circuit, and the terminal device side or exchange side When the communication request signal detection circuit detects a communication request signal from one of the
This is achieved by an automatic return loop creation circuit in the selection circuit, which is characterized in that the return circuit is open.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. FIG. 2 is a block diagram of an automatic return loop creation circuit provided in a terminal device of a subscriber line in a data exchange network according to an embodiment of the present invention, and FIG. 3 is a diagram showing the automatic return loop creation circuit shown in FIG. FIG. 2 is a signal sequence diagram that is exchanged between a creation circuit, a data exchanger, and a terminal device. Assuming that the terminal device is currently in a non-communication state, the signal path Ef from the data exchange SW and the signal path Df from the terminal device T are both in a non-communication state in the return loop automatic creation circuit. The no-communication state detection circuit 3 in FIG. 2 detects the no-communication state of the signal path Ef, and the no-communication state detection circuit 5 detects the no-communication state of the signal path Df, and the output signal S1 of both circuits 3 and 5 is and S
2 sends a set signal S to flip-flop circuits 8 and 10 through gate 12. The signal S
The output signal F1 of the flip-flop circuit 8 set by S connects the input I0 of the selection circuit 1 to the output, and the output signal F2 of the flip-flop circuit 10 set by the signal S connects the input I0 of the selection circuit 9 to the output. Connect to. Therefore, there is a delay circuit 2 and a path LP between the signal path Ef from the data exchanger SW and the signal path Eb leading to the data exchanger SW.
and a return loop passing through the selection circuit 1, and a signal path Db leading to the terminal device T.
The no-communication state signal Db1 is sent from the no-communication state signal generating circuit 7 via the selection circuit 9 (before time ta in FIG. 3). At time ta in FIG. 3, a communication request signal is sent from the terminal device T to the signal path Df.
When Df2 arrives, the communication request signal detection circuit 6 shown in FIG. 2 detects the communication request signal Df2 and sends a reset signal R2 to the flip-flop circuit 8 via the gate 13. Also, the no-communication state detection circuit 5 stops the output signal S2 and the set signal S being sent to the flip-flop circuit 8 via the gate 12. The flip-flop circuit 8 is therefore reset and its output signal F1 disconnects the input I0 of the selection circuit 1 from the output and connects the input I1 to the output. As described above, the feedback loop circuit being formed between the signal paths Ef and Eb for the data exchanger SW is cut off, and the communication request signal Df2 sent from the terminal device T onto the signal path Df is transmitted by the delay circuit 12 at the time t1. After receiving a delay of , it is sent out as a communication request signal Eb2 via the selection circuit 1 onto the signal path Eb leading to the data exchange SW. Further, the output signal R2 of the communication request detection circuit 6 is sent by the delay circuit 11 to the flip-flop circuit 10 as a reset signal R3 via the gate 14 after time t2. Therefore, the flip-flop circuit 10 is reset,
The output signal F2 disconnects the input I0 of the selection circuit 9 from the output and connects the input I1 to the output.
On the other hand, the data exchange SW which has received the communication request signal Ef2 via the subscriber line sends a response signal Ef3 to the terminal device T. The response signal Ef3 arrives on the signal path Ef at time tb in FIG. Sent as Db3. With the above steps, the signal path Df is
and Eb and Ef and Db are respectively connected, and the terminal device T and data exchange SW are in a communicable state. When the signal path Df from the terminal device T becomes non-communicative at time tc in FIG. 3 after the end of communication,
Via the delay circuit 12 and the selection circuit 1, the time t
After 1, the signal path Eb leading to the data exchanger SW is also in a non-communication state. Subsequently, at time td in FIG. 3, when the signal path Ef from the data exchanger SW also goes into a no-communication state, the signal path Db leading to the terminal device T after time t3 via the delay circuit 2 and selection circuit 9 also goes into a no-communication state. becomes. The non-communication state of the signal paths Df and Ef is detected by the non-communication state detection circuits 5 and 3, respectively, and the output signals S1 and S of both circuits 3 and 5 are detected.
2 sends a set signal S to flip-flop circuits 8 and 10 via gate 12. Flip-flop circuit 8 set by the set signal S
The output signal F1 causes the selection circuit 1 to disconnect the input I1 from the output and connect the input I0 to the output. Further, the output signal F2 of the flip-flop circuit 10 set by the set signal S causes the selection circuit 9 to disconnect the input I1 from the output and connect the input I0 to the output. Therefore, the signal path from the data exchanger SW
Between Ef and the signal path Eb leading to the data exchanger SW, there is again a delay circuit 2, a path LP, and a selection circuit 1.
A return loop is formed via the terminal device T, and a no-communication state signal is sent from the no-communication state signal generation circuit 7 via the selection circuit 9 to the signal path Db leading to the terminal device T.
Db1 is sent again. It takes time t4 from the end of communication on the signal path Db until the no-communication state signal Db1 is sent out. Next, when the communication request signal Ef2 arrives at the signal path Ef from the data exchanger SW at time te in FIG. 3, the communication request signal detection circuit 4 shown in FIG. 2 detects the communication request signal Ef2, and the gate 13 and A reset signal R1 is sent to flip-flop circuits 8 and 10 via 14. Further, the output signal S1 of the no-communication state detection circuit 3 is stopped, and the output signal S1 from the gate 12 to the flip-flop circuit 8 is stopped.
And the set signal S being sent to 10 is stopped.
Therefore, the flip-flop circuit 8 is reset,
The output signal F1 disconnects the input I0 of the selection circuit 1 from the output and connects the input I1 to the output.
Further, the output signal F2 of the reset flip-flop circuit 10 disconnects the input I0 and output of the selection circuit 9, and connects the input I1 to the output. Therefore, the return loop being formed between the signal paths Ef and Eb to the data exchanger SW is released, and the signal path Ef
The communication request signal Ef2 that has arrived is delayed for a time t3 by the delay circuit 2, and then sent out on the signal path Db to the terminal device T via the selection circuit 9 as the communication request signal Db2. Subsequently, the response signal Df3 that arrives on the signal path Df from the terminal device T at time tf in FIG. Response signal on road Eb
It is sent as Eb3, and the data exchange SW and terminal device T become communicable.

As is clear from the above explanation, according to this embodiment, in the automatic return loop creation circuit provided in the subscriber line termination device, the data exchange SW
A return loop is automatically formed between the signal paths Ef and Eb when there is no communication, and a signal for creating a return loop is sent from the data exchange SW to measure the transmission quality of the subscriber line. There is no need to send it to the end device. Also, the terminal device T
Or, if the communication request signal Df2 or Ef2 is sent from the data exchange SW to the subscriber line, the feedback loop automatic creation circuit immediately returns to the data exchange SW.
The return loop being formed between the signal paths Ef and Eb for the terminal device T is released, and the signal path for the terminal device T is
Connect Df and Db to enable communication. Therefore, the signaling system used for subscriber lines is
This is not affected in any way by the transmission quality measurement of the subscriber line performed from the data exchange SW side. Moreover, by automatically forming a return loop, loss of communication service to the subscriber is avoided.

Note that FIGS. 2 and 3 are only one embodiment of the present invention, and for example, the automatically created return loop is not limited to the signal paths Ef and Eb for the data exchange SW, but also for the signal paths Ef and Eb for the terminal device T. It may be considered to create the signal path between the signal paths Df and Db, or further on the signal path for both the data exchange SW and the terminal device T, but the effects of the present invention do not change in either case. Further, the installation location of the automatic return loop creation circuit is not limited to the subscriber line termination device, and the effects of the present invention will remain the same even if it is installed, for example, in a repeater. Furthermore, the type of communication network is not limited to a data exchange network.

As described above, according to the present invention, it is possible to constantly measure and monitor the transmission quality of a subscriber's line without affecting the signal system used in the subscriber's line and without impairing the communication service provided to the subscriber. A return loop automatic creation circuit can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional intra-network transmission quality measurement and monitoring method in a data exchange network, FIG. 2 is a configuration diagram of an automatic return loop creation circuit according to an embodiment of the present invention, and FIG. FIG. 3 is a signal sequence diagram on a signal path for the data exchanger and terminal device in the figure. In the figure, N...data exchange network, T1, T
2, T... terminal device, TE1, TE2... terminal device, L1, L2... subscriber line, SW1, SW2,
SW...Data exchanger, M1...Error rate measuring device,
M2...measuring section, Ef, Eb, Df, Db...signal path,
1, 9... Selection circuit, 2, 11, 12... Delay circuit, 7... No communication state signal generation circuit, 8, 10...
...Flip-flop circuit, 3, 5...No communication state detection circuit, 4, 6...Communication request signal detection circuit, 1
2, 13, 14...Gate, Db1...No communication state signal, Df2, Eb2, Ef2, Db2...Communication request signal, Ef3, Db3, Df3, Eb3...Response signal.

Claims (1)

[Claims] 1. A no-communication state detection circuit installed in the subscriber line between the terminal device and the exchange, which detects a no-communication state on the exchange side and the terminal device side, respectively, and a communication circuit that detects a communication request signal on the exchange side and the terminal device side, respectively. It has a request signal detection circuit, and when both of the no-communication state detection circuits detect a no-communication state, a return loop is formed in the selection circuit, and a communication request signal from either the terminal device side or the exchange side is detected. An automatic return loop creation circuit characterized in that a return circuit in a selection circuit is opened when a communication request signal detection circuit detects a communication request signal.