JP2002247191A - Failure line inspection system in adsl system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure line inspection system in an ADSL system which transmits an analog voice signal and a high-speed digital data signal through one subscriber line, that can simply and quickly conduct a work while maintaining the transmission of the analog voice signal through the subscriber line being a detection object and inspect a failure line of the ADSL system without giving any hindrance on other subscriber lines. SOLUTION: A subscriber line 18 connected to a subscriber side of a telephone station side in the ADSL system is connected to an ADSL MODEM 22 and a telephone exchange 28 via an MDF(Main Distribution Frame) 30 and a splitter 24, an inspection line changeover terminal panel 32 is provided to a connector connection between the MDF and the splitter so as to maintain the connection between the subscriber line and the telephone exchange and cutting off or bypassing the subscriber line and the inter-terminal connection between the splitter and the ADSL MODEM to inspect a failure line in the ADSL system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ADSL system for transmitting an analog voice signal and a high-speed digital data signal through one subscriber line, and to both ends of a subscriber line connecting a telephone office and a subscriber. When detecting a failure of an ADSL modem connected to a telephone line, it is possible to work easily and easily while utilizing the transmission of the analog voice signal of the subscriber line to be detected, particularly at the central office, and to perform other subscriptions. AD without any hindrance to the subscriber line
The present invention relates to a failed line inspection system capable of inspecting a failed line of an SL system.

[0002]

2. Description of the Related Art ADSL (Asymmetric Digital Sub)
scriber Line: Asymmetric Digital Communication Network)
This is a system that performs high-speed data communication using an existing analog telephone line (copper twisted pair line). This ADS
In the L system, ADSL modems are provided at both ends of a subscriber line connecting a telephone station and a subscriber. This ADSL modem is a data modulation / demodulation device for performing ADSL communication, and is characterized in that it handles a higher frequency than a normal analog modem. In addition, existing subscriber lines, that is, analog telephone lines
When connecting an SL modem, POTS is used to separate / synthesize the analog voice signal and the high-speed digital data signal.
(Plain Old Telephone Service) splitter or the like is used. This splitter separates the low frequency band of 10 kHz or less used in conventional analog telephone line services or these analog communications, and is installed at both ends of the telephone line. Connected to a telephone or telephone exchange,
Connect the other to an ADSL modem. With such a connection configuration, high-speed digital data communication via the ADSL modem is always possible regardless of the communication state of the analog telephone.

FIG. 8 shows a system configuration of a conventional ADSL system. As shown in FIG.
In the DSL system, high-speed digital data received by a high-speed digital data communication device (PC) 10 on the subscriber side is modulated and demodulated by an ADSL modem 12 and then transmitted via an integrated separation device (splitter) 14 to analog data on the subscriber side. The analog voice signal transmitted and received by the telephone set 16 is integrated and separated in a frequency-divided state, and is transmitted and received to and from the telephone station side B via the same subscriber line 18. Similarly, on the telephone station side B, high-speed digital data from the high-speed digital data communication network (Internet) 20 is
After being modulated / demodulated by the ADSL modem 22, the analog voice signal transmitted / received between the analog telephone line network 26 and the telephone exchange 28 connected by the integration / separation device (splitter) 24 is integrated / separated in a frequency-divided state. Thus, the data is transmitted / received to / from the subscriber side A via the same subscriber line 18.

[0004] When such an ADSL system is constructed, generally, the central office B has an MDF (Main Dis- tribution).
The telephone exchange 28 and the subscriber line 18 are connected to each other by a terminal board composed of a distribution frame (central distribution board) 30. FIG. 9 is an explanatory diagram of the case where the subscriber line 18 is connected to the telephone exchange 28 and the ADSL modem 12 using the MDF 30. Note that in FIG.
The H terminal 30a of the F30 is on the connection side with the subscriber line 18, and the V terminal 30b of the MDF 30 is on the connection side with the telephone exchange 28.

When the subscriber line 18 using the MDF 30 is connected to the telephone exchange 28 and the ADSL modem 12, the subscriber line for 20 people is usually regarded as one unit via the terminal board and the H terminal 30a of the MDF 30 is connected. And the V terminal 30b and the integrated separation device (splitter) 24 are connected to each other with a connector. The analog audio signal split from the integration / separation device (splitter) 24 is transmitted to the telephone exchange 28 via the H terminal 30a and the V terminal 30b of the MDF 30, and the split high-speed digital data signal is transmitted to the ADSL. Transmitted to the modem.

[0006]

However, in the ADSL system having such a configuration, for example, when a failure occurs in high-speed digital data communication when a subscriber line used by a certain subscriber is used, the telephone station side. When investigating the cause of a failure in the ADSL system, it is necessary to cut off the failed line in the splitter in which the ADSL modem is connected to the MDF. In this case, the ADS
Since a plurality of subscriber lines (for 20 to 30 lines) are generally connected to the splitter connected to the L-modem in a lump, if the connector connection of the splitter to the MDF is cut off, a failure occurs. This will hinder communication on the subscriber's line where no error occurs. Further, in this case, there is a disadvantage that transmission of an analog audio signal separated from a high-speed digital data signal becomes impossible.

The inventor of the present invention has made intensive studies and studies in order to solve the above-mentioned problems, and as a result, the analog telephone on the subscriber side and the telephone exchange on the central office are connected by one subscriber line. ADS configured to multiplex an analog voice signal and a high-speed digital data signal on the subscriber line by frequency division or time division, and to concentrate and transmit the signal to the subscriber line.
When the L system is constructed, the telephone line connects a subscriber line connected to the subscriber side to an ADSL modem and a telephone exchange via an MDF and a splitter, and further connects a plurality of lines between the MDF and the splitter. By providing a test line switching terminal board when connecting a connector via a subscriber line, when testing a failure of a subscriber line of one subscriber, the test line switching terminal board is used to connect to the subscriber line. Maintaining a connection with a telephone exchange, a subscriber line of said one subscriber, said splitter and ADSL
By configuring so that only the connection between the terminals with the modem can be interrupted, the transmission of the analog voice signal of the subscriber line to be detected is utilized, and there is no problem with other subscriber lines. It has been found that the inspection of a faulty line of the ADSL system can be performed easily and simply without any influence.

That is, the inspection line switching terminal board includes two types of terminal boards, each of which is composed of a pair of terminals connected to an H terminal and a V terminal which are interconnected with a subscriber line of the MDF and a telephone exchange. The other end of each pair of terminals of the terminal board is always connected to the splitter at all times, and a line switching plug is inserted between the pair of terminals connected to each other to cut off the connection between the terminals and to connect the connection-side H terminal. And interconnecting the connection side V terminal with the subscriber line and the telephone exchange to maintain the transmission of the analog voice signal of the subscriber line to be detected as described above, and to connect to other subscriber lines. Inspection of a faulty line of the ADSL system can be performed easily and simply without causing any trouble. Then, the units constituting the inspection line switching terminal board, the splitter, and the ADSL modem are separately housed and arranged in one rack together with the power supply unit and the monitoring unit, so that the inspection of the failure line of the ADSL system can be performed. In addition, it can be performed easily and easily without impairing the function of the analog telephone in the subscriber line.

Accordingly, an object of the present invention is to provide an ADSL system for transmitting an analog voice signal and a high-speed digital data signal through a single subscriber line, and in particular, when detecting a failure in the ADSL system at the central office, the subscriber to be detected. While the transmission of the analog voice signal of the subscriber line is maintained, the operation can be performed simply and quickly, and the AD can be performed without any trouble to other subscriber lines.
AD that can check for faulty lines in SL system
An object of the present invention is to provide a faulty line inspection method in an SL system.

[0010]

In order to achieve the above-mentioned object, a faulty line inspection system in an ADSL system according to the present invention is a method for connecting a subscriber's analog telephone and a central office telephone exchange to one subscriber's line. ADSL system comprising an analog telephone network connected and connected to each other, and multiplexing and concentrating an analog voice signal and a high-speed digital data signal on the subscriber line for transmission. Side, and an ADSL modem and a telephone exchange via an MDF and a splitter, and an inspection line switching terminal board is provided between the MDF and the splitter for connection. And a telephone exchange, and the subscriber line, the splitter and the ADS.
Disconnect or detour connection between terminals with L-modem and AD
It is characterized in that a faulty line of the SL system is inspected.

In this case, the inspection line switching terminal board includes:
Two types of terminal boards each comprising an H terminal and a V terminal interconnected with the subscriber line of the MDF and the telephone exchange, respectively, are provided, and the other end of each of these terminal boards is always connected to the splitter. And the connection is cut off by being inserted between a pair of terminals of the one terminal board connected to each other, and the connection side H terminal and connection side V terminal of the MDF are connected to a subscriber line and a telephone exchange. And a line switching plug for interconnecting with the line.

Further, one end of the inspection line switching terminal board is connected to a predetermined subscriber line and a telephone exchange via a connection side H terminal and a connection side V terminal of the MDF, and the other end is connected to a splitter. A regular line switch terminal board for inspection composed of two types of terminal boards each having a pair of terminals arranged so as to be connected to each other, and an unused subscriber at one end via a connection side H terminal and a connection side V terminal of the MDF, respectively. A dummy inspection line switching terminal board comprising two types of terminal boards each having a pair of terminals connected and connected to a line and a telephone exchange and connected to the splitter at the other end. The connection between the paired terminals, which are inserted and connected to each other through the line switching terminal board and the dummy inspection line switching terminal board, is cut off, and the paired terminal and the dummy terminal are connected. A configuration in which a pair of line switching plugs are provided, which are provided with contact terminals to be connected to each other, and are connected in a bypass manner between the regular inspection line switching terminal board and the dummy inspection line switching terminal board by a common switching line. can do.

Further, the units constituting the inspection line switching terminal board, the splitter, and the ADSL modem are separately housed and arranged in one rack together with the power supply unit and the monitoring unit, so that the ADSL is provided.
Inspection of a faulty line of the system can be performed easily and simply without impairing the function of the analog telephone in the subscriber line and the function of high-speed digital data communication by the ADSL modem.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a failure line inspection system in an ADSL system according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a system configuration of an ADSL system according to the present invention. For the sake of convenience, the same components as those of the conventional ADSL system shown in FIG. 9 described above will be described with the same reference numerals. That is, in FIG. 1, the basic system configuration of the ADSL system according to the present invention is the same as the above-described conventional system configuration.

In FIG. 1, ADSL according to the present embodiment is shown.
On the subscriber side, the high-speed digital data received by the high-speed digital data communication device (PC) 10 is modulated and demodulated by the ADSL modem 12 and then transmitted to the analog-side device of the subscriber via an integrated separation device (splitter) 14. The analog voice signal transmitted and received by the telephone set 16 is integrated and separated in a frequency-divided state, and is transmitted and received to and from the telephone station side B via the same subscriber line 18.

On the telephone station side B, high-speed digital data from a high-speed digital data communication network (Internet) 20 is modulated and demodulated by an ADSL modem 22 and then transmitted via a splitter 24 and an MDF 30 to an analog telephone network. An analog voice signal transmitted / received between the telephone exchange 28 and the telephone exchange 28 is integrated and separated in a frequency-division or time-division multiplexed state and transmitted / received to / from the subscriber side A via the same subscriber line 18. It is configured to be.

In the ADSL system according to the present embodiment, the telephone line B connects the subscriber line 18 connected to the subscriber A to the ADSL modem 22 and the telephone exchange 28 via the MDF 30 and the splitter 24. In this case, an inspection line switching terminal board 32 is provided between the connector connection between the MDF 30 and the splitter 24.

However, the inspection line switching terminal board 32
As shown in FIG. 2, the subscriber line 18, the telephone exchange 28, the connection-side V terminal 30a and the connection-side H terminal 30b of the MDF 30 are connected to each other by a paired terminal, Two types of terminal boards 32a and 32b each having a pair of terminals always interconnected with the splitter 24.
Consists of

FIG. 3 shows the inspection line switching terminal board 3 described above.
2 shows a specific configuration example. That is, FIG.
Indicates a terminal board 32a connected to the connection-side V terminal 30a of the MDF 30. The subscriber line 18 and the telephone exchange 28 and the connection side V terminal 30a of the MDF 30 are connected to the inspection line switching terminal board 32a configured as described above.
Are provided with paired terminals 32V and 32V 'which are connected to each other, and paired terminals 33V and 33V' which always connect these paired terminals 32V and 32V 'to the splitter 24. And the inspection line switching terminal board 3
A line switching plug 34 is provided which can cut off the connection between the terminals by being inserted between the paired terminals 32V and 33V and between 32V 'and 33V' of FIG.
(A) and (b)]. Although not shown, the terminal board 32b connected to the connection-side H terminal 30b of the MDF 30 has exactly the same configuration as the terminal board 32a.

In FIGS. 4A and 4B, the line switching plug 34 is connected to the pair of terminals 32 connected to each other.
Contact terminals 36V which are in conductive contact with the pair terminals 32V, 32V 'and 33V, 33V' above and below an insulating substrate 35 which can be inserted between V and 33V, 32V 'and 33V'.
, 36V 'and 37V, 37V' are provided, and each of the contact terminals 36V, 36V 'and 37V, 37V' is connected to a switching line 38 having four lead wires insulated and separated from each other.

Therefore, by applying the line switching plug 34 to the inspection line switching terminal board 32 as described above, the inspection line switching terminal board 32 corresponding to the subscriber line 18 to be detected is set. , 32V 'and 33V', and 32V 'and 33V', respectively, can be cut off. At the same time, the terminals 32V and 3
3V, 32V 'and 33V' are contact terminals 36V, 37V, 36V 'and 37V provided on the line switching plug 34, respectively.
′ Are brought into conductive contact with each other, and are respectively separated and conducted to the lead wires of the switching line 38.

Therefore, in the present invention, a dummy inspection line switching terminal board 32 'having exactly the same configuration is provided for the inspection line switching terminal board 32, and these inspection line switching terminal boards 32 are provided. On the other hand, by applying the line switching plug 34 having the switching line 38, the ADSL
Inspection of a faulty line of the system can be performed easily and simply.

FIG. 5 is an explanatory diagram showing an outline of a line switching operation for inspecting a failed line of the ADSL system using the inspection line switching terminal board 32 and the line switching plug 34. That is, in FIG. 5, each pair is arranged so that one end is connected to a predetermined subscriber line 18 and a telephone exchange 28 via the connection side V terminal 30a of the MDF 30 and the other end is connected to the POTS splitter 24, respectively. Regular inspection line switching terminal board 32a having terminals 32V and 33V, 32V 'and 33V'
And a pair of terminals 32V each having one end connected to the unused subscriber line 18 and the telephone exchange 28 via the connection side V terminal 30a of the MDF 30 and the other end connected to the POTS splitter 24, respectively. 3
A dummy inspection line switching terminal board 32a 'having 3V, 32V' and 33V 'is provided.

On the other hand, the regular inspection line switching terminal board 3
As shown in FIG. 6, contact terminals 36V and 37V, 36V 'and 37V', which are inserted and connected to the 2a and dummy inspection line switching terminal boards 32a ', respectively, are connected by a common switching line 38. A pair of line switching plugs 3
4, 34 'are provided.

An operation for checking a failed line when, for example, an ADSL system of one subscriber has failed will be described with reference to FIG. First, one of the line switching plugs 34 is inserted into the designated pair terminals 32V and 33V and 32V 'and 33V' of the regular inspection line switching terminal board 32a. As a result, the connection between the paired terminals 32V and 33V, 32V 'and 33V' in the interconnected regular inspection line switching terminal board 32a is cut off, and the paired terminals 32V and 33V and 32V 'and 33V' are disconnected.
Are the contact terminals 36V and 3 of the line switching plug 34, respectively.
7V, 36V 'and 37V' are brought into contact. Thereby, the P connected to the ADSL modem 22 to be tested is
OTS splitter 24 and failed subscriber line 1
Only the connection line to the MDF 30 connected to the subscriber line 8 can be cut off without affecting the other subscriber lines 18 at all.

Next, the one line switching plug 34 'connected to the one line switching plug 34 and the switching line 38 is connected to the dummy inspection line switching terminal board 32.
a 'is inserted into the paired terminals 32V and 33V, and 32V' and 33V '. As a result, the contact terminals 36V and 37V, 36V 'and 37V' of the line switching plug 34 'are respectively connected to the paired terminals 32V and 3V of the dummy inspection line switching terminal board 32a'.
Contact conduction is made between 3V, 32V 'and 33V'. As a result, the MDF connected to the failed subscriber line 18
30 is connected to the line switching plugs 34, 34 '.
And detour via the switching line 38, and the telephone exchange 2
8, the function of the analog telephone can be maintained, and the function of the high-speed digital data communication by the ADSL modem can be maintained.

In the above-described embodiment, when the line switching plugs 34, 34 'are to be alternately connected between the inspection line switching terminal boards 32a, 32a' via the switching line 38, the switching of the line switching plugs 34, 34 'is performed. If the line 38 is a cross cable, the line switching plugs 34, 34 'symmetrically connected and disposed at both ends thereof are inserted up and down so as to be inserted into the inspection line switching terminal boards 32a, 32a', respectively. If the switching line 38 is a straight cable, the line switching plugs 34, 3 symmetrically connected and arranged at both ends thereof
4 'may be turned upside down and inserted into the inspection line switching terminal boards 32a, 32a', respectively.

In the above-described inspection of the faulty line of the ADSL system, the connection side V terminal 30 of the MDF 30 is used.
Inspection line switching terminal boards 32a, 32a 'connected to a
H terminal 3 on the connection side of the MDF 30 not shown
Inspection line switching terminal boards 32b, 32 connected to 0b
For b ', the line switching plug 34 as described above,
The operation by the switch 34 'and the switching line 38 is unnecessary (see FIG. 7). In this case, as is clear from FIG.
For a failure in the connection line between the inspection line switching terminal board 32a connected to the connection side V terminal 30b of the MDF 30 and the POTS splitter 24, the POTS splitter 24 is not used via the dummy inspection line switching terminal board 32a '. By making a detour connection with this line, the above-described inspection of a failed line or the like can be easily performed.

In FIG. 7, the inspection line switching terminal board 32 connected to the connection side H terminal 30b of the MDF 30 is used.
The terminals b and 32b 'are connected to the inspection line switching terminal board 32 connected to the connection-side V terminal 30a of the MDF 30 shown in FIG.
a, 32a ', 32V, 32V' and 33V,
Reference numerals 32H, 32H 'correspond to 33V', respectively.
And 33H, 33H '.

As described above, according to the present invention, the ADS
When a faulty line is to be inspected when a fault occurs in the L system, the central office, on the side of the central office, handles AD which handles high-speed digital data signals after the splitter connected to the MDF
The connection line of the SL modem can be separated from the telephone line that handles analog audio signals by providing a line switching terminal board for inspection. Therefore, the units constituting the inspection line switching terminal board, the splitter, and the ADSL modem are separately housed and arranged in one rack together with the power supply unit and the monitoring unit, so that the telephone line is completely separated. In this way, it is possible to quickly and easily inspect the failed line of the ADSL system.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.
RADSL (Rate Adapt) derived from the DSL system
iveAsymmetric Digital Subscriber Line) system and HDSL (High data rate Digital S)
ubscriber Line system, VDSL (Very High)
Speed Digital Subscriber Line) System, S
Not only can it be applied to a DSL (Symmetric Digital Subscriber Line) system or the like, but also many other design changes can be made without departing from the spirit of the present invention.

[0033]

As is apparent from the above-described embodiment, according to the faulty line inspection system in the ADSL system according to the present invention, the analog telephone on the subscriber side and the telephone exchange on the central office are connected by one subscriber line. In an ADSL system comprising an analog telephone line network constituted by being connected to each other and multiplexing and concentrating an analog voice signal and a high-speed digital data signal on the subscriber line and transmitting the multiplexed signal, the subscriber side at the telephone station side Connected to the ADSL modem and the telephone exchange via the MDF and the splitter, and a test line switching terminal board is provided between the connector connection between the MDF and the splitter, and the subscriber line is connected to the subscriber line. Stay connected to the telephone exchange,
And the connection between the terminals of the subscriber line and the splitter and the ADSL modem is interrupted or detour-connected and the ADSL
By checking the system for faulty lines,
In a state where the transmission of the analog audio signal of the subscriber line to be detected is maintained, the inspection of the failed line of the ADSL system can be performed easily and simply without causing any trouble to other subscriber lines. Can be done quickly.

In the faulty line inspection system in the ADSL system according to the present invention, one end of each of the inspection line switching terminal boards is connected to a predetermined subscriber line via a connection side H terminal and a connection side V terminal of the MDF. And a regular inspection line switching terminal board composed of two types of terminal boards each having a pair of terminals connected to a telephone exchange and connected to the splitter at the other end, and a connection side H of the MDF at one end. To an unused subscriber line and a telephone exchange via a terminal and a connection side V terminal,
A dummy inspection line switching terminal board composed of two types of terminal boards each having a pair of terminals arranged so as to connect the other end to the splitter, and inspecting the regular inspection circuit switching terminal board and the dummy. A connection terminal for connecting the pair of terminals, which are inserted and interconnected with each other, and a contact terminal for connecting to each of the pair of terminals. By providing a pair of line switching plugs for bypass connection between the terminal board and the dummy inspection line switching terminal board, the workability of the inspection of the failed line of the ADSL system can be properly, promptly and efficiently achieved. be able to.

[Brief description of the drawings]

FIG. 1 shows an AD adopting a faulty circuit inspection system according to the present invention.
FIG. 1 is a schematic explanatory diagram showing one embodiment of a system configuration of an SL system.

FIG. 2 is an explanatory diagram showing a detailed configuration example of a line switching terminal board for inspection of the ADSL system shown in FIG. 1;

3 is a schematic explanatory view showing a configuration example of a test line switching terminal board of the ADSL system shown in FIG. 2;

FIG. 4 shows an example of a configuration in which the line switching terminal board for inspection shown in FIG. 3 and a line switching plug applied thereto are combined.
(A) is a schematic side view, (b) is a schematic plan view.

FIG. 5 is a schematic explanatory view in a case where a line switching operation is performed using the inspection line switching terminal board shown in FIG. 3;

6 is a schematic explanatory view showing a line switching operation state by a combination of a line switching terminal board for inspection and a line switching plug shown in FIG. 4;

FIG. 7 is an explanatory diagram showing a detailed configuration example in a case where a line switching operation is performed using the inspection line switching terminal board shown in FIG. 4;

FIG. 8 is a schematic explanatory view showing the principle of a conventional ADSL system.

FIG. 9 is a schematic explanatory diagram showing a system configuration example of a conventional ADSL system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 High-speed digital data communication equipment (PC) 12 ADSL modem 14 Integrated separation equipment (splitter) 16 Analog telephone 18 Same subscriber line 20 High-speed digital data communication network (Internet) 22 ADSL modem 24 Integrated separation equipment (splitter) 26 Analog telephone Circuit network 28 Telephone exchange 30 MDF (central distribution board) 30a V terminal (connection side in telephone office) 30b H terminal (subscriber line connection side) 32 Inspection line switching terminal board 32a, 32b Regular inspection line switching terminal board 32a ', 32b' Dummy inspection line switching terminal board 32V, 32V 'and 33V, 33V' Counter terminal 32H, 32H 'and 33H, 33H' 34, 34 'Line switching plug 35 Insulating board 36V, 36V' and 37V, 37V 'contact terminal 38 Switching line A Subscriber side B Central office side

Claims (4)

[Claims] 1. An analog telephone network comprising an analog telephone on a subscriber side and a telephone exchange on a central office connected by a single subscriber line, wherein the subscriber line has an analog voice signal and a high-speed signal. In an ADSL system configured to multiplex digital data signals and concentrate and transmit the signals, a subscriber line connected to a subscriber side at a central office is
Connecting to the ADSL modem and the telephone exchange via the MDF and the splitter, and providing an inspection line switching terminal board between the connector connection between the MDF and the splitter;
A configuration in which the connection between the subscriber line and the telephone exchange is maintained, and the connection between the terminals of the subscriber line and the splitter and the ADSL modem is cut off or alternately connected to check the failed line of the ADSL system. A fault line inspection method in an ADSL system, characterized in that: 2. The test line switching terminal board according to claim 1, wherein
The terminal has two types of terminal boards each of which is connected to an H terminal and a V terminal which are interconnected with a subscriber line of F and a telephone exchange, and the other end of each of these terminal boards is always connected to the splitter. Interconnected, and further inserted between the pair of terminals of the one terminal board to be interconnected to cut off the connection, and the connection side H terminal and connection side V terminal of the MDF are connected to a subscriber line and a telephone exchange. 2. A faulty line inspection system in an ADSL system according to claim 1, further comprising a line switching plug for interconnection. 3. The inspection line switching terminal board has one end connected to a predetermined subscriber line and a telephone exchange via a connection side H terminal and a connection side V terminal of the MDF, and the other end connected to a splitter. A regular line switch terminal board for inspection composed of two types of terminal boards each having a pair of terminals arranged so as to be connected to each other, and an unused subscriber at one end via a connection side H terminal and a connection side V terminal of the MDF, respectively. A dummy inspection line switching terminal board comprising two types of terminal boards each having a pair of terminals connected and connected to a line and a telephone exchange and connected to the splitter at the other end. A line switching terminal board and a dummy inspection line switching terminal board are respectively inserted into and interconnected with the paired terminals, and each of the paired terminals is disconnected from the paired terminals. A contact switching terminal, and a pair of line switching plugs for bypassing between the regular inspection line switching terminal board and the dummy inspection line switching terminal board by a common switching line. 3. A failure line inspection system in the ADSL system according to claim 1 or 2. 4. The system according to claim 1, wherein the units constituting the inspection line switching terminal board, the splitter, and the ADSL modem are housed separately in a single rack together with a power supply unit and a monitoring unit. 4. A faulty line inspection method in the ADSL system according to any one of claims 1 to 3.