JP2000031963A - Isdn network terminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To notify that the cause of not making a call out is due to failure occurrence on a network side by returning a DISC message to which the reason display of why the network is out of order or a REL message by forcedly starting a layer 1 with an ISDN terminal device and disconnecting a call out in a case such as when a failure takes places in the network side and call out processing can not be performed. SOLUTION: When a timer makes timeout before a U point controlling part 34 detects a SIG 3 (inversion) from a subscriber exchange, it forcedly makes a user network interface I a starting state with a facsimile machine. And, a SETUP message is transmitted and it is received by a D channel controlling part 35 of a network terminating device 2. As a result, a main controlling part 30 controls the part 35, transmits a DISC message to the facsimile machine and disconnects a call. And, the facsimile machine is notified that the call is disconnected because a failure takes place on the side of the network.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ISDN network terminating device.

[0002]

2. Description of the Related Art In an ISDN terminal device connected to a user / network interface in an ISDN basic interface, phantom power may be supplied from a network side, so that communication is required in order to prevent power supply from being wasted. A layer 1 activation / deactivation procedure that activates an interface only when communication is not required and deactivates it when communication is not required is described in ITU-T Recommendation I.T. 430.

As shown in FIG. 7, a facsimile machine 1 is an ISDN terminal (TE: Terminal Equivalent).
user / network interface I
When the facsimile apparatus 1 is connected to the ISDN via the (S / T point), the facsimile apparatus 1 is connected to the ISDN network terminating apparatus 2 on the network (ISDN) side. The network terminating device 2 is connected to a local exchange 3 in the ISDN via a local line L.

[0004] In an ISDN terminal device (TE) such as the facsimile device 1, as shown in FIG. 8, the INFO 0 signal is exchanged with the network terminating device 2 in the layer 1 in the stopped state, as shown in FIG. When the network terminating device 2 is stopped, the SIG0 signal is exchanged with the local exchange 3.

[0005] When the facsimile apparatus (TE) 1 issues an activation request to the layer 1 due to the activation of the call processing in the upper layer of the D channel, it transmits an INFO 1 signal to the network terminating apparatus 2. Upon receiving the INFO1 signal from the facsimile machine (TE) 1, the network terminating device 2 closes the DC loop of the subscriber line L and transmits the SIG2 signal to the local exchange 3. That is, a loop is formed on the subscriber line. Upon receiving the SIG2 signal from the network terminating device 2, the local exchange 3 transmits the SIG3 signal by inverting the power supply polarity of the subscriber line L, and transmits the SIG3 signal.
After performing the synchronization signal procedure by exchanging the SIG4 and SIG5 signals with the network device 1, a request for activating the layer 1 is made to the network terminating device 2 by the SIG6 signal. The network termination device 2
Upon receiving the SIG6 signal from the local exchange 3, IN
The FO2 signal is transmitted to the facsimile machine (TE) 1.

A facsimile apparatus (TE) 1 is an INFO
When a signal is received from the network terminating device 2 after transmitting one signal, I
The transmission of the NFO1 signal is stopped. Facsimile machine (T
E) 1 indicates that the signal received from the network termination device 2 is INFO2
If the signal is a signal, frame synchronization is established and an INFO3 signal is transmitted to the network termination device 2. The network termination device 2 receives the signal and exchanges the SIG8 signal and the SIG7 signal with the local exchange 3, The facsimile apparatus (TE) 1 that has transmitted the INFO4 signal to the facsimile apparatus 1 and has received the INFO4 signal enters an active state, and thereafter exchanges the INFO3 and 4 signals, and exchanges layer 1 level frames. It becomes possible.

[0007] When the layer 1 is activated, under the control of the upper layer of the D channel, a calling process is performed, and the B channel is connected to the partner terminal to perform communication.

[0008]

On the other hand, at the same time that the facsimile machine (TE) 1 sends out the INFO1 signal, the facsimile machine (TE) 1 starts a so-called T3 timer.

Then, the facsimile apparatus (TE) 1
If the T3 timer has timed out between the start request by the NFO1 signal and the reception of the INFO4 signal from the network termination device 2, that is, if the layer 1 could not be started within a predetermined time, After transmitting the INFO0 signal (no signal), the state returns to the stop state, and the layer 1 cannot be activated.

In the case where the T3 timer times out, the network terminating device 2 sends the I
The SI between the network terminating device 2 and the local exchange 3 between the reception of the NFO1 and the transmission of the INFO4 signal.
It is conceivable that the time required for the exchange of the G signal becomes abnormally long due to some trouble. Specifically, the network control unit 2 sends the I / O signal from the facsimile machine (TE) 1
Although SIG2 (loop) is transmitted to the local exchange 3 after receiving the NFO1, the local exchange 3 does not recognize the SIG2, or the SIG2 is recognized.
If IG3 (reciprocity) is not returned, the network control unit 2
This is the case where the subsequent layer 1 activation procedure cannot be performed with the local exchange 3.

As described above, the facsimile apparatus (TE) 1
When the T3 timer times out on the side, the layer 1 cannot be activated, so that the call processing at the layer 3 cannot be performed, but the user cannot know that the cause of the failure to make the call is a failure on the network side. There was a point.

The present invention has been made in view of the above circumstances, and can notify an ISDN terminal device connected via a user / network interface that a cause of failure to make a call is a failure occurrence on the network side. An object of the present invention is to provide an ISDN network termination device.

[0013]

In order to achieve the above object, an ISDN network terminating device according to claim 1 is connected to an ISDN terminal device via a user network interface and is connected to the ISDN terminal via a subscriber line. Is connected to the local exchange, and in the stop state, the INFO
When receiving one signal, a loop is formed on the subscriber line,
Thereafter, when the polarity reversal detecting means detects the polarity reversal of the subscriber line by the subscriber exchange, the ISDN terminal device that activates layer 1 by exchanging a predetermined signal with the ISDN terminal device and the subscriber exchange. ISD
A timer means for measuring an elapsed time after forming a loop in the subscriber line in response to the reception of the INFO1 signal from the N terminal apparatus; and the timer means for counting the elapsed time before the elapsed time counted by the timer means reaches a predetermined time. If the anti-detection means does not detect the polarity reversal of the subscriber line, a predetermined INFO signal is exchanged with the ISDN terminal to forcibly activate layer 1 with the ISDN terminal. Network failure handling means for returning a DISC message or a REL message to which a message indicating a network failure has been added to a SETUP message received from the ISDN terminal device in layer 3 on the activated layer 1 It is characterized by.

According to a second aspect of the present invention, there is provided an ISDN network termination device according to the first aspect of the invention, wherein the network failure handling means adds a reason indication of a network failure to the ISDN terminal device. Or RE
Even after returning the L message, the loop formed in the subscriber line is maintained, and the reciprocity monitoring means for monitoring the reversal of the polarity of the subscriber line. If a SETUP message is received from the ISDN terminal device at layer 3 before detection, a DISC message or R
Network failure immediate response means for returning an EL message.

According to a third aspect of the present invention, in the ISDN network terminating apparatus according to the second aspect, the reciprocity monitoring means detects a reversal of the polarity of the subscriber line and performs layer 1 operation.
The method further comprises a layer 1 holding means for always starting layer 1 without activating the layer 1 disconnection procedure when the start of the layer 1 is successful.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described in detail.

FIG. 1 shows a block configuration of an ISDN network terminating apparatus 2 according to an embodiment of the present invention.

In FIG. 1, the ISDN network terminating device 2
It comprises a main controller 30, an ISDN interface 31, a layer 1 controller 32, a subscriber line interface 33, a U point controller 34, a D channel controller 35, and a data interface 36.

As shown in FIG. 7, the ISDN network terminating device 2 is connected to the facsimile device 1 as an ISDN terminal device via a user network interface I (S / T point) of an ISDN basic interface. It is connected to the local exchange 3 in the ISDN via the subscriber line L and controls layers 1 to 3 with the ISDN terminal device.

In FIG. 1, the main control unit 30 includes an MPU,
This is for controlling the operation of the entire apparatus by a microcomputer including a RAM, a ROM, a timer, and the like.
The ISDN interface 31 corresponds to the ISDN basic interface, serves as a physical interface with the facsimile machine 1 which is an ISDN terminal device, and performs physical transmission and reception of signals via the user / network interface I. Interface.

The layer 1 control unit 32 exchanges layer 1 frames via the ISDN interface 31,
Under the control of the main control unit 30, a layer 1 start / stop procedure and the like are performed. The subscriber line interface 33 serves as a physical interface with the local exchange 3, and is a physical interface for transmitting and receiving signals via the subscriber line L. The U point controller 34 exchanges signals with the local exchange 3 via the subscriber line interface 33 and performs a layer 1 start / stop procedure under the control of the main controller 30.

The D channel control unit 35 controls the D channel protocols of the D channel layers 2 and 3, and controls the transmission of the LAPD frame in the layer 2 and the call control such as the setting and release of the call in the layer 3. It is for doing. The data interface 36
This is for relaying data between the layer 1 control unit 36 and the U point control unit 34.

Next, the ISDN according to the embodiment of the present invention
FIG. 2 shows a block configuration of the facsimile device 1 as an ISDN terminal device connected to the network terminating device 2.

Referring to FIG. 1, a facsimile apparatus 1 includes a system controller 11, a ROM 11, a RAM 13, a scanner 14, a plotter 15, an image memory 16, a clock circuit 17,
Parameter memory 18, backup circuit 19, operation display unit 20, encoding / decoding unit 21, ISDN interface 22, layer 1 control unit 23, D channel control unit 2
4, G4 communication control unit 25, G3 communication control unit 26, COD
It comprises an EC 27 and a system bus 28.

The system control unit 11 controls each unit of the apparatus according to the control program written in the ROM 12 while using the RAM 13 as a work area.

As described above, the ROM 12 is a read-only memory in which a control program for the system control unit 11 to control each unit of the apparatus is stored. RAM1
Reference numeral 3 denotes a random access memory used as a work area of the system control unit 11 as described above.

The scanner 14 is 200 × 200 pixels / 2
5.4 mm (1 inch), 300 × 300 pixels / 25.
This is for obtaining image information by reading a document image at a predetermined reading line density of 4 mm, 400 × 400 pixels / 25.4 mm or the like. The plotter 15 converts the received image information into
This is for recording and outputting according to the resolution and for recording and outputting (copying operation) the image information read by the scanner 14 according to the linear density.

The image memory 16 temporarily stores image information read by the scanner 14 as a file for transmission to the memory, or temporarily stores received image information as a file until it is recorded by the plotter 15. Or something to do. The clock circuit 17 counts the current time and counts down a timer value set from the system control unit 11 and times out.
To perform a timer operation to notify. The parameter memory 18 stores various changeable parameters related to the operation of the apparatus, and is backed up by a backup circuit 19, and the stored contents are retained even when the apparatus is powered off. In the parameter memory 18, FIG.
As shown in (3), a T3 timer value which is a set value of the T3 timer started at the time of starting the layer 1 is stored.

The operation display unit 20 includes a numeric keypad, a start key, a one-touch dial key, and other various keys (not shown) for designating a destination telephone number, and a display such as a liquid crystal display device. It displays the operating status of the device to be notified to the user and various messages.

The encoding / decoding unit 21 converts the transmission image information into G
3 or G4 facsimile, MH coding method, MR coding method, MMR coding method, while encoding and compressing the received image information, MH coding method, MR coding method, The decoding is performed by a predetermined decoding method corresponding to the MMR coding method or the like.

The ISDN interface 22 is an ISD
N basic interface, ISDN
(Network terminating device 2), which is a physical interface for transmitting and receiving signals via the user / network interface I. The layer 1 control unit 23 exchanges layer 1 frames via the ISDN interface 22,
This controls the stop procedure and the like. D channel control unit 2
4 controls the D channel protocol of the D channel layers 2 and 3;
It is for performing transmission control of a PD frame and call control such as setting and release of a call in layer 3.

The G4 communication control section 25 controls G4 facsimile communication with the G4 facsimile apparatus of the other party, which is performed using the B channel set by the D channel control section 24. G3 communication control unit 26
Is for controlling G3 facsimile communication with the G3 facsimile machine of the other party performed using the B channel set by the D channel control unit 24.

The CODEC 27 is interposed between the G3 communication control unit 26 and the layer 1 control unit 23, and
3 is converted into an analog signal on the B channel and input to the G3 communication control unit 26.
3 is for converting an analog modem signal from the communication control unit 26 into a digital signal and inputting it to the layer 1 control unit 23. The system bus 28 is a signal line through which the above components exchange data.

The facsimile apparatus 1 configured as described above reads the document set on the scanner 14 and stores the image information stored in the image memory 16 in the G3 of the destination facsimile apparatus designated from the operation display unit 20. The encoding and decoding unit 21 compresses and encodes the G4
Using the communication control unit 25 or the G3 communication control unit 26,
The image information received from the ISDN is transmitted to the destination device by the B channel set by the D channel control unit 24, and the image information received from the ISDN is transmitted to the G4 communication control unit 25 or G3 according to the type of the destination device, G3 or G4. The image data is received using the communication control unit 26, stored in the image memory 16, and is encoded / decoded.
1, the data is decoded and decompressed, and the plotter 15 records and outputs it on recording paper.

The layer 1 of the facsimile apparatus 1 is in a stopped state except during such a communication operation, and when the facsimile apparatus 1 calls the ISDN, the facsimile apparatus 1
Transmits an INFO1 signal to the ISDN network terminating device 2 to make a layer 1 activation request. 430
It is necessary to perform a layer 1 start / stop procedure based on the above, and start layer 1.

FIG. 4 shows an ITU-T in an ISDN terminal device.
Recommendation I. A partial transition state related to the present invention in the layer 1 start / stop procedure based on H.430 is shown.

In the figure, the stopped state (state number F3)
Transmits an INFO0 signal, that is, a no signal, to the ISDN network terminating device 2 side. Then, when an activation request is issued to the layer 1 from an upper layer, the state transits to a signal waiting state (state number F4) and the T3 timer is started.

In the signal waiting state, an INFO1 signal is transmitted to the network side, and waits until some signal is received from the network side.
When any signal is received from the network side, the state transits to the input identification state (state number F5) and transmits the INFO0 signal to the network side. If the T3 timer times out in the input identification state, the state returns to the stop state.

In the input identification state, if the signal received from the network side is the INFO2 signal, the synchronization state (state number F
The state transits to 6) and transmits the INFO3 signal. If the T3 timer times out in the synchronized state, the state returns to the stopped state.

When the signal received from the network side in the input identification state is the INFO4 signal, or when the INFO4 signal is received from the network side in the synchronous state, the state transits to the activation state (state number F7), and INFO3 Send a signal. In the activated state, when the INFO0 signal is received from the network side, the state transits to the suspended state.

As described above, when a call is made from the ISDN terminal device, when the layer 1 transmits the INFO1 signal from the stopped ISDN terminal device to the ISDN network terminating device 2 to request the start, the layer 1 is activated when the INFO1 signal is transmitted. T3
The timer receives the INFO4 signal from the network side, waits for a signal before transitioning to the active state, input identification information, or
If a timeout occurs in the synchronous state, the mobile terminal returns to the stop state without shifting to the active state, and cannot start the layer 1 and cannot perform call setting in the D channel layers 2 and 3.

The timer value of the T3 timer is a fixed value arbitrarily set by the designer of the ISDN terminal device.
As shown in FIG. 8, for some reason, a signal exchange between the network terminating apparatus 2 and the local exchange 3 is delayed, and the ISDN terminal equipment (TE) sends IN to the network terminating apparatus 2.
The time from transmission of the FO1 signal to transmission of SIG2 (loop) from the network controller 2 to the local exchange 3 to reception of SIG3 (reverse) from the local exchange 3 becomes abnormally long. The time until the signal is transmitted to the ISDN terminal becomes abnormally long, during which the T3 timer in the ISDN terminal may time out.

In that case, in the ISDN terminal device,
Even if the calling process is started in the layer 3, the layer 1 returns to the stopped state without being started, and the call fails only. It is impossible to know that the call has failed due to the occurrence of a failure on the network (ISDN) side.

Therefore, the ISDN network terminating apparatus 2 according to the present embodiment performs the processing procedures shown in FIGS. 5 and 6 so that the layer 1 cannot be activated due to the occurrence of a failure on the network (ISDN) side. The ISDN terminal device can be notified that the reason is the occurrence of a failure on the network side.

The processing procedure shown in FIGS. 5 and 6 will be described.

First, in FIG. 5, the main control unit 30 monitors reception of INFO1 from the facsimile apparatus 1, which is an ISDN terminal apparatus, when the layer 1 is stopped (No loop of the judgment 101). When received by the control unit 32, the U-point control unit 34
2 is sent to the local exchange to form a loop on the subscriber line L. Then, the main control unit 30 starts the timer Tr (process 103). Note that the time constant of the timer Tr started in the process 103 is set to a value smaller than the value set as the T3 timer value in the facsimile machine 1. This is because if the T3 timer is timed out on the facsimile apparatus 1 before the timer Tr is timed out in the determination 104 to be described later and the activation of the layer 1 from the facsimile apparatus 1 is stopped, the reason for the call failure is the facsimile failure. This is because it is not possible to distinguish whether the failure of the device 1 has occurred on the network side.

After the timer Tr is started in the process 103, while monitoring whether the timer Tr has timed out,
SIG3 (reverse) from the local exchange 3 is the U point control unit 3
4 is detected (No in decision 104,
No loop of decision 105). Then, if SIG3 is detected before the timer Tr times out, that is, if no failure has occurred on the network side and the network is normal (judgment 1
05) Thereafter, the layer 1 is started up between the facsimile machine 1 and the local exchange 3 in the sequence shown in FIG. 8, and the normal processing starts from the reception of the SETUP message from the facsimile machine 1 in the layer 3. (Step 106).

If the timer Tr times out before SIG3 is detected (Yes in decision 104), the process proceeds to the process 107 in FIG. In the process 107 of FIG. 6, the IN received from the determination 101 with the facsimile machine 1
The S / T point (user / network interface I) is forcibly brought into the active state by returning to the active state in which INFO2 is returned in response to the FO1 signal and INFO4 is transmitted and INFO3 is received (process 107).

Then, the SET from the facsimile machine 1
The reception of the UP message is monitored (No loop of the judgment 108). When the facsimile apparatus 1 starts the layer 1,
SE in layer 3 on the activated layer 1
A TUP message is transmitted, which is received by the D channel control unit 35 of the network termination device 2.

Then, the judgment 108 becomes Yes, and the main controller 30 controls the D channel controller 35 to
Sending an SC message to the facsimile machine 1;
The call is disconnected when viewed from the facsimile machine 1. However, actually, since the layer 1 between the network termination device 2 and the local exchange 3 has not been activated, the situation is different from the case where a normal call is disconnected. Therefore, the DIS transmitted in process 108
As the reason display information element of the C message, "network failure (#
38) "or a value indicating a failure of the subscriber line. As a result, the facsimile machine 1 is notified that the reason why the call was disconnected is the occurrence of a failure on the network side, and is displayed on the display unit of the operation display unit 20 so that the facsimile apparatus 1 can send a call to the user. It can be informed that the reason for the call failure is a network-side failure. Note that in process 109, D
Instead of the ISC message, a REL message may be transmitted.

By transmitting the DISC message in step 109, the call from the facsimile machine 1 in the case where a failure has occurred on the network side is notified that the reason why the call was disconnected is the failure on the network side. You can cut while
At that time, SIG2
(Loop), the local exchange 3 still has SIG3
(Rebellion) has not been returned.

Therefore, after the processing 109, the U point control unit 3
4 to monitor whether the SIG3 from the local exchange 3 is detected and whether or not the D channel control unit 35 receives the SETUP message from the facsimile machine 1 (No in the judgment 110, No in the judgment 111). loop).

When the SETUP message is received in the layer 3 (in this case, the activation of the layer 1 is performed only with the facsimile apparatus 1 as in the case of the processing 107) (decision 111). Similarly to the processing 109, a DISC message is transmitted to the facsimile apparatus 1 (processing 112), and the process returns to the determination 110.

Thus, when a second call is made when a fault has occurred on the network side, the facsimile machine 1
Layer 1 is immediately activated forcibly to receive the SETUP message, and the received SETUP message is sent to the network failure (# 3
8) DIS such as a value indicating a failure of the subscriber line
C message can be returned without delay.

In the determination 110, the process continues to wait for the detection of SIG3 (reverse), but the fault occurring on the network side is resolved, and the local exchange 3 reverses the polarity of the subscriber line L. And the judgment 110 is Yes, the procedures of SIG4 and SIG5 can be executed with the local exchange 3, and the local exchange 3
If the layer 1 between them can be activated, the synchronization with the local exchange 3 is not released as it is, so that the activated layer 1 is set to be always activated (process 113).

As a result, the layer 1 with the facsimile apparatus 1 can be activated immediately in response to a subsequent layer 1 activation request from the facsimile apparatus 1, and the call processing in the layer 3 on the layer 1 can be smoothly performed. It can be carried out.

In the above-described embodiment, the present invention is applied to the ISDN network terminating device 2 to which the facsimile device 1, which is one of the ISDN terminal devices, is connected. However, the present invention is not limited to this. The present invention can be similarly applied to an ISDN terminal device to which other ISDN terminal devices are connected.

[0058]

According to the first aspect of the present invention, the IS
The calling process is started in the DN terminal device, and the layer 1
INFO1 signal requesting activation of the subscriber line, and the local exchange switches the local exchange after a certain time has elapsed since the ISDN network terminating apparatus according to the present invention forms a loop in the subscriber line in response to the INFO1 signal. If the polarity of the subscriber line is not reversed, that is, if a failure occurs on the network side and the T3 timer times out in the ISDN terminal device and the layer 1 stops, the call processing cannot be performed. In such a case, the layer 1 between the ISDN terminal device is forcibly activated, and a DISC message or a REL message to which a cause of network failure is added is added to the SETUP message received from the ISDN terminal. In response, the call cannot be made to the ISDN terminal device because the call is cut off as viewed from the ISDN terminal device. The cause can be notified that a failure has occurred on the network side, and the notified reason can be displayed on the ISDN terminal device or the like, thereby notifying that the call could not be made due to the failure on the network side. A possible effect is obtained.

According to the second aspect of the present invention, the ISD
DI with indication of network failure reason for N terminal
Even after returning the SC message or the REL message, the loop formed on the subscriber line is maintained to monitor the polarity reversal of the subscriber line, and the ISDN terminal device is layer 3 at layer 3 before the polarity reversal is detected. From SETUP
When the message is received, a DISC message or a REL message to which the cause of the network failure is added is returned. That is, a DISC message or REL message to which a reason indication of a network failure has been added once due to the occurrence of a failure on the network side.
After returning the message and disconnecting the call as viewed from the ISDN terminal, the ISDN terminal returns
When an ETUP message is received (in that case, the IS
Since the layer 1 between the network and the DN terminal apparatus is forcibly activated in the same manner as in the first aspect of the present invention, it is known that the fault occurring on the network side has not been eliminated. By returning the DISC message or the REL message to which the reason indication during the network failure is added, it is unnecessary to make a call to the ISDN terminal device (the user of the ISDN terminal device) because the failure has occurred on the network side. The effect of being able to notify quickly without having to wait is obtained.

According to the third aspect of the invention, if the polarity reversal monitoring means detects the reversal of the polarity of the subscriber line and succeeds in starting the layer 1, the layer 1 disconnection procedure is performed temporarily. It is necessary to perform the layer 1 activation procedure again at the time of the next call, and if the time until the polarity reversal of the subscriber line is detected in the layer 1 activation procedure is long, the call from the ISDN terminal apparatus is disconnected. In view of the fact that normal call processing cannot be performed, the layer 1
Is always activated, so that even if there is a problem on the network side, it is possible to obtain an effect that the call processing can be smoothly performed at the next call.

[Brief description of the drawings]

FIG. 1 is a diagram showing a block configuration of an ISDN network termination device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a block configuration of a facsimile machine 1 as an ISDN terminal device connected to an ISDN network terminal according to an embodiment of the present invention.

FIG. 3 is a diagram showing the contents stored in a parameter memory of a facsimile machine as an ISDN terminal device connected to the ISDN network termination device according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a partial transition state in a layer 1 start / stop procedure.

FIG. 5 is a flowchart showing a processing procedure in the ISDN network terminal according to the embodiment of the present invention.

FIG. 6 is an ISD according to an embodiment of the present invention, together with FIG. 4;
It is a flowchart which shows the processing procedure in an N network termination device.

FIG. 7 shows a facsimile device as an ISDN terminal device,
FIG. 2 is a diagram illustrating a connection form of an ISDN network termination device and a local exchange;

FIG. 8 is a diagram showing an example of an activation sequence of Layer 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 facsimile apparatus 2 network terminator 3 subscriber exchange 11 system control unit 12 ROM 13 RAM 14 scanner 15 plotter 16 image memory 17 clock circuit 18 buffer memory 19 backup circuit 20 operation display unit 21 encoding / decoding unit 22 ISDN interface 23 layer 1 control unit 24 D channel control unit 25 G4 communication control unit 26 G3 communication control unit 27 CODEC 28 system bus 30 main control unit 31 ISDN interface 32 layer 1 control unit 33 subscriber line interface 34 U point control unit 35 D channel control unit 36 Data Interface

Continued on the front page F term (reference) 5K019 AC09 BA61 BB39 CD03 CD11 DA05 DC03 5K030 GA12 HC05 JA08 JL08 JT00 JT05 KA14 LB01 LB12 MB01 MB20 5K101 LL03 MM04 PP06 RR11 TT03 VV01 VV03

Claims (3)

[Claims] 1. An Internet connection via a user / network interface
SDN terminal device and I
When connected to a local exchange in the SDN and receiving an INFO1 signal from the terminal device in a stopped state, a loop is formed in the local line, and then a reversal of the polarity reversal of the local line by the local exchange is detected. When the means detects, in an ISDN network terminating device that activates layer 1 by exchanging predetermined signals with the ISDN terminal device and the local exchange, the subscriber line is transmitted in response to reception of an INFO1 signal from the ISDN terminal device. A timer means for counting the elapsed time after the loop is formed, and if the reversal detection means does not detect the reversal of the subscriber line before the elapsed time counted by the timer means reaches a predetermined time. A predetermined INFO signal is exchanged with the ISDN terminal device to
Forcibly activates layer 1 between the terminal and the SDN terminal device.
In response to the SETUP message received from the terminal device,
An ISDN network terminating device comprising: a network failure handling means for returning a DISC message or a REL message to which an indication of a network failure has been added. 2. The method according to claim 2, wherein
DIS to which reason indication of network failure is added to the terminal device
Even after replying C message or REL message,
A reciprocity monitoring means for holding a loop formed on the subscriber line and monitoring the reversal of the polarity of the subscriber line; and When a SETUP message is received from an ISDN terminal device, DI indicating the cause of the network failure is added.
2. The ISDN network termination device according to claim 1, further comprising a network failure immediate response unit that returns an SC message or a REL message. 3. The layer 1 holding means for always activating layer 1 without activating the layer 1 disconnection procedure when the polarity reversal monitoring means detects the reversal of the polarity of the subscriber line and successfully activates layer 1. 3. The apparatus according to claim 2, further comprising means.
2. The ISDN network termination device according to claim 1.