Abstract:
The present invention provides two subscriber line testing systems, three broadband/narrowband telecommunication systems and a broadband line card. In the subscriber line testing systems of the present invention, a test module is configured in the CO broadband device, reducing the complexity and the cost of the subscriber line testing systems. In the broadband line card provided by the present invention, line capturing relays are configured in the broadband line card so that the LPF card can be designed as a passive device to reduce corresponding costs, thus using this broadband line card helps reduce the complexity of the CO broadband device and the subscriber cost thereof. In the three broadband/narrowband telecommunication systems provided by the present invention, by using the subscriber line testing systems and the broadband line card, the complexity of broadband/narrowband telecommunication systems and subscriber cost thereof are also reduced. In the third broadband/narrowband telecommunication system provided by the present invention, both the broadband line card without line capturing relay and the broadband line card with line capturing relay can be incorporated so that a better compatibility is provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation Application of International Application Number PCT/CN2004/000788, filed on Jul. 12, 2004, which claims priority of Chinese Patent Application Number 03147382.2, filed on Jul. 12, 2003, and Chinese Patent Application Number 03154405.3, filed on Sep. 27, 2003. 

   FIELD OF THE TECHNOLOGY 
   The present invention relates to line testing techniques in the telecommunication field, more particularly, to a subscriber line testing system as well as broadband line card and broadband/narrowband telecommunication system. 
   BACKGROUND OF THE INVENTION 
   In the telecommunication field, operators are able to simultaneously provide broadband ADSL or VDSL telecommunication service as well as narrowband telecommunication services (POTS/ISDN service) via copper twisted pair, e.g. ADSL over POTS (Plain Old Telephone Service), ADSL over ISDN, and VDSL over POTS, and such applications are already quite common. In the present invention, ADSL and VDSL are referred to as xDSL, namely X Digital Subscriber Line. 
   In order to enable a telecommunication system provide services of such applications, it is required that, corresponding to each copper twisted pair, namely, to each subscriber, a Low Pass Filter (LPF, generally called a separator), a low-frequency (POTS or ISDN) signal service processing circuit, a High Pass Filter (HPF) and a high-frequency signal (xDSL signal) processing circuit be configured at the Central Office (CO) and the Customer Premises Equipment (CPE), respectively, so as to connect the copper twisted pair, i.e. the subscriber. 
   A typical broadband/narrowband telecommunication system in the prior art is shown in  FIG. 1 , wherein a subscriber external line  1  of the CPE equipment  1 ˜n are connected to a Main Distribution Frame (MDF)  15  of CO, the MDF  15  connects the subscriber external line  1  to a broadband access device (DSL Access Multiplexer, DSLAM)  14  of CO via electric cables  3  and  6  as well as to a narrowband exchange device  13  of CO via an electric cable  19 . 
   There is a mixed signal composed of a high-frequency xDSL. signal and a low-frequency POTS/ISDN signal on the subscriber external line  1 . At the CO side, the subscriber external line  1  is physically connected to the CO broadband DSLAM  14  through an external line module  17  on a frame  9  of MDF  15 , a jumper  20  and an internal line module  2  of MDF and then through the internal electric cable  3 . 
   Inside the broadband DSLAM  14  at CO, there are at least one separator (LPF) card  5 , at least one broadband line card  7 , a power supply unit and a master control module  16 , wherein the broadband line card  7  is an xDSL line card. 
   The mixed signal on the subscriber external line  1  is output to LPF card  5  and broadband line card  7 , wherein each LPF card  5  comprises a number of (n) LPF circuits and each LPF circuit performs as a low-pass filter for filtering the mixed signal of its corresponding subscriber line, and then the separated narrowband signal (POTS/ISDN signal) is transmitted to the narrowband line card in the narrowband device  13  (POTS card or ISDN card) at CO through an internal line module  8 , a jumper  21 , an internal line module  18  and an electric cable  19  of the MDF  15  for service processing, and each narrowband line card comprises a number of (m) service processing circuits. 
   Inside each broadband line card  7 , there are a number of (p) High Pass Filters (HPF) as well as the same number (p) of xDSL service processing circuits (ATU-C). After each HPF has filtered the low-frequency POTS/ISDN signal of its corresponding subscriber line, the corresponding xDSL service processing circuit (ATU-C) will perform a service processing of the xDSL signal. 
   The narrowband switching device  13  at CO comprises a narrowband line card as well as a master control and a narrowband service processing module. 
   The processing at CPEs  1 ˜n is similar to the processing at CO, wherein CPE separator (LPF) separates the narrowband signal from the mixed signal of subscriber external line  1  and sends the narrowband signal to the subscriber&#39;s phone set, and meanwhile the mixed signal is transmitted to a Remote Telephone Unit (RTU), the High Pass Filter (HPF) configured inside the RTU filters the low-frequency POTS/ISDN signal from the mixed signal and then performs a service processing of the high-frequency signal (xDSL signal). 
   In practical applications, the number of ports comprised in each external line module of the distribution frame is usually equal to the number of ports comprised in each internal line module of the distribution frame; a typical case comprises 128 ports or 100 ports. (Note: the so called external/internal line module of distribution frame is the connector bank of twisted pair, and two connectors corresponding to a twisted pair is called one port). 
   Each LPF card comprises a number of circuits for connecting a number of subscriber lines, for example, 32 circuits can connect 32 subscriber lines. Likewise, each narrowband line card also comprises a number of circuits, say 32 or 16 circuits; so does each broadband line card, say 32 or 48. A LPF card, a broadband line card and a narrowband line card do not necessarily comprise the same number of circuits, respectively. A LPF card and a broadband line card are usually configured as comprising the same number of circuits respectively. 
   In  FIG. 1 , there is a line test module  22  configured at CO for use in testing subscriber line malfunction. 
   In practical applications, since the subscriber external line  1  between CPE and CO MDF is located outdoors, it is prone to have a malfunction due to touching other lines, getting disconnected, touching a power line, getting immerged or other external reasons. Therefore, a proper testing device is set at CO for measuring parameters of the subscriber line, such as line voltage, line resistance, line capacitance, line background noise, and line balance degree to ground, so as to detect and identify malfunctions and make malfunction reports. Based on the malfunction reports, a telecommunication operator can arrange its personnel to repair the line malfunctions. 
   The line test module  22  is usually located in a device or system outside DSLAM, or located in a module inside DSLAM. 
   In order to enable line test module  22  to test every subscriber line connected to DSLAM, it is required to configure at each subscriber interface circuit a switching device for switching connecting directions of a subscriber line, which is usually referred to as a “line capturing test relay” or switching test relay. The function of a line capturing test relay, i.e. “line capturing test”, is to switch a subscriber line connected to the DSLAM subscriber interface circuit to the automatic test device for line malfunction. 
   In order to implement the “line capturing test”, it is needed to set a “line capturing test relay” in each subscriber interface circuit of each LPF card, of which the operating principle is shown in  FIG. 2 .  FIG. 2  is a schematic diagram illustrating the operating principle of a line capturing test relay in  FIG. 1 , wherein each subscriber line must pass a line capturing relay  12  before entering the LPF circuit  11  and the broadband line card  7 . 
   It can be seen from  FIG. 2  that, when the line testing device is not testing subscriber lines, a subscriber external line is directly connected to the service processing circuit at CO (LPF  11 , HPF on broadband line card  7  and ATU-C  10 ) through the closing contact of line capturing relay  12  (shown by the solid line in  FIG. 2 ), namely the subscriber line and CO circuit are connected as normal. When the automatic test device is testing the first subscriber external line, the connecting direction of this subscriber external line will be switched through line capturing relay  12  and then this subscriber external line will be connected to the line testing device  22  via a test bus  23 , while subscriber external lines of other subscribers and CO circuits are still normally connected. 
   In practical applications, LPF circuit  11  is composed of capacitors, inductors and other passive electronic devices. If there are no other active electronic circuits or devices in the internal circuit of a LPF card, this LPF card can be a passive circuit board. However, in the technical scheme of the prior art as shown in  FIG. 2 , since a line capturing test relay of the subscriber line is set inside an LPF card and the relay cannot operate without power supply, the LPF card needs to introduce power supply from the system back board in the cabinet of the DSLAM so as to supply power to the line capturing relay. Therefore, an LPF card in such a case is an active circuit component and cannot normally operate when disengaged from the system back board in the DSLAM cabinet, namely the LPF card cannot be separated from the DSLAM cabinet which has a power supply component configured in it; in addition, an active LPF card circuit board is more complicated than a passive one. 
   As the line capturing relay set in the LPF card of the broadband DSLAM at CO increases the complexity of LPF card, a second type of broadband/narrowband telecommunication system has emerged. As shown in  FIG. 3 , which is a schematic diagram illustrating the second type of broadband/narrowband telecommunication system in prior art, a test device is set between the original MDF  15  and the DSLAM  14  at CO. The test device is composed of a line capturing matrix module  24  and a test module  25 , wherein the line capturing matrix module  24  captures a designated subscriber line for the test module  25 , and the test module  25  tests the parameters of this line, such as electric resistance, capacitance, voltage, background noise, longitudinal degree of balance and etc. The test module  25  can also be implemented by an external test device. 
   In this broadband/narrowband telecommunication system, all line capturing relays are separated from the LPF card and set inside one line capturing matrix module  24  so that a large number of commercial “LPF cards without line capturing relays” already employed in this field can be used continuously. 
   The test device of the broadband/narrowband telecommunication system as shown in  FIG. 3  is rather complicated as it has to perform such functions as power collecting, communications with DSLAM, line capturing/line release, and line testing. If an external test device is adopted to implement the functions of a test module, the line capturing matrix device and the test device have to get power supply and communicate with DSLAM, respectively, which further increases the complexity of the entire system. 
   Besides, since an entrance port and an exit port must be set inside the test device for the wiring of each subscriber line, the test device has to comprise a large number of ports, leading to the massive size and high price of the test device as well as a pretty high average cost for each subscriber. 
   SUMMARY OF THE INVENTION 
   In view of the above, an embodiment of the present invention, in one aspect, provides two kinds of subscriber line testing systems, which are applicable to broadband/narrowband telecommunication systems and able to reduce the complexity thereof and lower the subscribers&#39; cost. 
   In another aspect, another embodiment of the present invention provides a broadband line card for broadband devices at CO so that the complexity of broadband devices at CO could be reduced and the subscriber&#39;s cost lowered. 
   In yet another aspect of the present invention, three broadband/narrowband telecommunication systems with less complexity and lower subscribers&#39; cost are provided. 
   According to the first aspect mentioned above, the embodiment of the present invention provides two kinds of subscriber line testing systems. 
   One subscriber line testing system provided in the present invention is used in a broadband/narrowband telecommunication system, comprising a line capturing matrix device connected between a distribution frame and a CO broadband device of the broadband/narrowband telecommunication system, and a line test module, wherein 
   the test module is configured inside the CO broadband device and is connected to the line capturing matrix device and a master control module in the CO broadband device, respectively, and the test module receives a test command from the master control module and instructs the line capturing matrix device to act according to the command; 
   the line capturing matrix device captures a designated subscriber external line according to the command and switches the line to the test module; and 
   the test module tests the captured subscriber external line, obtains a test result and reports the test result to the master control module. 
   The line test module and line capturing matrix device in the CO broadband device are connected by a cable interface. 
   The other subscriber line testing system provided in the present invention is used in a broadband/narrowband telecommunication system, comprising a line capturing unit and a line test module, wherein 
   the line capturing unit comprises all line capturing relays connected in series to subscriber lines; 
   the test module is configured inside a CO broadband device and is connected to a master control module in the CO broadband device and all the line capturing relays, respectively; 
   the line capturing relays capture a designated subscriber external line according to a line capturing command from the master module and switches the captured line to the line test module; and 
   the line test module receives a test command from the master control module, tests the captured subscriber external line and reports a testing result obtained to the master control module. 
   According to the second aspect mentioned above, the present invention provides a broadband line card for the broadband device at CO, comprising a high pass filter circuit and a broadband service processing circuit of each subscriber line, and further comprising a line capturing relay of each subscriber line, wherein 
   the line capturing relay of each subscriber line is connected in series to a corresponding subscriber line. 
   According to the third aspect mentioned above, the present invention provides three broadband/narrowband telecommunication systems with less complexity and lower subscriber cost. 
   The first broadband/narrowband telecommunication system provided by the present invention comprises CPEs, a CO devices, and a line testing system; wherein the CO devices comprise a CO broadband device and a CO narrowband device, the line testing system comprises a line capturing matrix device and a test module; and the CO broadband device comprises a separator card, a broadband line card and a master control module; 
   the CPE is connected to the CO broadband device and CO narrowband device, respectively, through a distribution frame and the line capturing matrix device, 
   the test module is configured inside the CO broadband device and connected to the line capturing matrix device and the master control module of the CO broadband device, respectively; the line test module receives a test command from the master control module and instructs the line capturing matrix device to act according to the command; 
   the line capturing matrix device captures a designated subscriber external line according to the instruction and switches the captured line to the line test module; 
   the line test module tests the captured subscriber external line and reports a test result obtained to the master control module. 
   The second broadband/narrowband telecommunication system presented by the present invention comprises CPEs, a CO devices, a line testing system; wherein the CO devices comprise a CO broadband device and a CO narrowband device, the line testing system comprises a line capturing device and a test module; and the CO broadband device comprises a separator card, a broadband line card and a master control module; 
   the line capturing unit comprises all line capturing relays connected in series with the subscriber line; 
   the test module is configured inside the CO broadband device and connected to the master control module and all the line capturing relays in the CO broadband device, respectively; 
   the line capturing relay captures a designated subscriber external line according to a command from the master control module and switches the captured line to the line test module; 
   the line test module receives the test command from the master control module, tests the captured subscriber external line according to the command and reports a test result obtained to the master control module. 
   The third broadband/narrowband telecommunication system provided by the present invention comprises CPEs, a CO devices, and a line testing system; wherein the CO devices comprises a CO broadband device and a CO narrowband device, the line testing system comprises a line capturing matrix device and a test module; and the CO broadband device comprises a separator card, a master control module and a broadband line card without line capturing relay, 
   the CO broadband device further comprises a broadband line card containing a line capturing relay; 
   the first group of lines of CPEs are connected to the separator card of the CO broadband device through a distribution frame and the line capturing matrix device, the separator card is connected to the broadband line card without line capturing relay; and this group of lines are connected to the CO narrowband device through the distribution frame and the line capturing matrix device; 
   the second group of lines of CPEs are connected to the separator card of the CO broadband device directly through another distribution frame, the separator card is connected to the broadband line card with line capturing relay; and this group of lines are connected to the CO narrowband device directly through the distribution frame; 
   the test module is configured in the CO broadband device and is connected to the line capturing matrix device and the master control module of the CO broadband device, respectively; 
   with the first group of lines, the line test module receives a test command from the master control module, instructs according to the command the relay in the line capturing matrix device to act so as to capture a designated subscriber external line and switch the line to the line test module; 
   with the second group of lines, the broadband line card receives a line capturing command from the master control module, the line test module receives the test command from the master control module, the broadband line card drives the relay according to the command to act so as to capture a designated subscriber external line and switch the line to the line test module; 
   the line test module tests the captured subscriber external line and reports a result obtained to the master control module. 
   According to the third aspect mentioned above, the present invention provides a broadband line card of CO device, comprising a high pass filter circuit and a broadband service processing circuit of each subscriber line, wherein this broadband line card further comprises a line capturing relay of each subscriber line; 
   the line capturing relay of each subscriber line is connected in series between the high pass filter circuit of this subscriber line and low pass filter circuit of this subscriber line. 
   It can be seen from the foregoing technique scheme that, in the two subscriber line testing systems provided by the present invention, a test module is set inside the CO broadband device which provides electric power and connection for the line capturing matrix device or line capturing unit so that complexity and the cost of the subscriber line testing system is reduced. This subscriber line testing system is applied in three broadband/narrowband telecommunication systems of the present invention and the complexity and subscriber cost thereof is reduced. In addition, the third broadband/narrowband telecommunication system comprises both broadband line card comprising no line capturing relay and broadband line card comprising line capturing relay, which renders the system a better compatibility. The broadband line card of CO broadband device provided by the present invention has the line capturing relay set on the broadband line card itself, which makes the LPF card a passive device and reduce the corresponding cost. As a result, application of this card can reduce the complexity of the CO broadband device as well as the subscriber&#39;s cost. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram illustrating the structure of one type of broadband/narrowband telecommunication system according to the prior art; 
       FIG. 2  is a schematic diagram illustrating the operating principle of the line capturing test relay in the structure shown in  FIG. 1 ; 
       FIG. 3  is a schematic diagram illustrating the structure of another type of broadband/narrowband telecommunication system according to the prior art; 
       FIG. 4  is a schematic diagram illustrating the structure of the broadband/narrowband telecommunication system according to a first preferred embodiment of the present invention; 
       FIG. 5  is a schematic diagram illustrating the connector between the test module and the line capturing matrix device in the embodiment shown in  FIG. 4 ; 
       FIG. 6  is the flowchart of the testing in the embodiment shown in  FIG. 4 ; 
       FIG. 7  is a schematic diagram illustrating the broadband/narrowband telecommunication system according to a second preferred embodiment of the present invention; 
       FIG. 8   a  is a schematic diagram illustrating a first kind of structure and connection of the broadband line card with line capturing relays in the embodiment shown in  FIG. 7 ; 
       FIG. 8   b  is a schematic diagram illustrating a second kind of structure and connection of the broadband line card with line capturing relays in the embodiment shown in  FIG. 7 ; 
       FIG. 8   c  is a schematic diagram illustrating a third kind of structure and connection of broadband line card with line capturing relays in the embodiment shown in  FIG. 7 ; 
       FIG. 8   d  is a schematic diagram illustrating a fourth kind of structure and connection of the broadband line card with line capturing relays in the embodiment shown in  FIG. 7 ; 
       FIG. 8   e  is a schematic diagram illustrating a fifth kind of structure and connection of broadband line card with line capturing relays in the embodiment shown in  FIG. 7 ; 
       FIG. 9  is a schematic diagram illustrating the broadband/narrowband telecommunication system according to a third preferred embodiment of the present invention; 
       FIG. 10  is the flowchart of the testing in the embodiment shown in  FIG. 9 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings. 
   In the subscriber line testing system and broadband/narrowband telecommunication system provided by the embodiments of this invention, the line test module of the line testing system is set in the CO broadband device. Next, three preferred embodiments of the present invention will be described in detail. 
   Preferred Embodiment 1 
   As shown in  FIG. 4 , which is a schematic diagram illustrating a broadband/narrowband telecommunication system according to a first preferred embodiment of the present invention, the first kind of broadband/narrowband telecommunication system provided by the present invention comprises CPEs  1 ˜n, a CO broadband device  14 , a CO narrowband device  13  and a line capturing matrix device  24 . The CO broadband device comprises an LPF card  5 , a broadband line card  7 , a master control module  16  and a line test module  25 . The Local narrowband device  13  comprises a CO narrowband line card, a master control module and a narrowband service processing module. 
   The Subscriber external lines  1  of the CPEs  1 ˜n are connected to the CO broadband device  14  and the CO narrowband device  13 , respectively, through an MDF  15  and the line capturing matrix device  24 . 
   The test module  25  of the present embodiment is configured in the CO broadband device and is connected to the line capturing matrix device  24  and the master control module  16  in CO broadband device, respectively, the test module  25  receives a test command from the master control module  16  and instructs the line capturing matrix device  24  to act according to the command. The line capturing device  24  captures the designated subscriber external line according to the instruction and switches the line to the line test module  25 . The line test module  25  tests the captured external line and reports a result obtained to the master control module  16 . 
   The line test module  25  and the line capturing matrix device  24  can be connected through an electric cable interface which comprises a communication interface, a power supply interface and a test bus interface. The line test module  25  communicates with the line capturing matrix device  24  through the communication interface, supplies electric power for the line capturing matrix device  24  through the power supply interface and tests the subscriber external line captured by the line capturing matrix device  24  through the test bus interface. 
   The line capturing matrix device  24  and the line test module  25  in the present embodiment constitutes the testing system of the embodiment of the present invention, which is controlled by the master control module  16  in the CO broadband device to carry out tests on subscriber lines. 
   In the present embodiment, the test module and the line capturing matrix device are connected by a DB15 connector, and at the test module side, three signals from the power supply interface, the communication interface and the test bus interface are merged on this physical connector. Refer to  FIG. 5 , which is a schematic diagram illustrating the structure of the connector connecting the test module with the line capturing matrix device in the embodiment as shown in  FIG. 4 . 
     FIG. 6  is the flowchart of the test in the embodiment shown in  FIG. 4 , and the specific test procedure is as follows: 
   Step  10 : the master control module of the CO broadband device receiving a command to initiate a test from outside and transmitting the command to the line test module; 
   The test command comprises: parameters concerning which subscriber external line to be tested, what kind of test to be performed, and etc; 
   Step  20 : after receiving the test command from the master control module, the line test module forwarding this command through the communication interface between the line test module and the line capturing matrix device, instructing the line capturing matrix device to act; 
   Step  30 : the line capturing matrix device capturing the designated subscriber external line so that this designated external line is connected to the test bus physically through a shot-circuit; 
   After finishing the capturing of a subscriber external line, the line capturing matrix device further reporting the completion of the line capturing to the line test module through the communication interface; 
   Step  40 : the line test module starts testing the subscriber line through the bus. The signal processing procedure of subscriber lines by the test module is the same as in the prior art. 
   Step  50 : after finishing testing the subscriber line, the line test module reporting a result to the master control module for subsequent processing. 
   Depending on the need of the test, the test result may be outputted by the master control module. 
   The line test module usually has the following functions: 
   Digital Multi Meter (DMM) test: testing items such as a direct current voltage, an alternate current voltage, a resistance, and a capacitance of the line; 
   Frequency Response (FR) and maximum attainable bit rate test: testing the frequency response of the line in connection with the frequency range of the xDSL; estimating the commissioning rate of the line. 
   Line background noise test: recognizing the noise type of the line, e.g. the interference noise of type E1, etc; 
   Line load coil test: detecting the number of inductances that are connected in series on the line and determining the location of the first inductance connected in series; 
   Longitudinal degree of balance test: testing the longitudinal degree of balance of the line; 
   Line length test: testing the length of the line; 
   Pulse noise test: detecting the pulse noise on the line. 
   Preferred Embodiment 2 
   Refer to  FIG. 7 , which is a schematic diagram illustrating the structure of a broadband/narrowband telecommunication system according to a second preferred embodiment of the present invention. This is a specific embodiment of a second kind of broadband/narrowband telecommunication system provided by the present invention, which comprises CPEs  1 ˜n; , a CO broadband device  14  and a CO narrowband device  13 . The CO broadband device comprises an LPF circuit  5 , a broadband line circuit  7 , a master control module  16  and a line test module  25 . The CO narrowband device  13  comprises a CO narrowband line card, a master control module and a narrowband service processing module. 
   Each subscriber line in CO broadband device  14  of the present embodiment is connected in series with a line capturing relay for use of testing the subscriber line (not shown in  FIG. 7 ), These relays are the line capturing units in the present embodiment. 
   The LPF circuit  5  and the broadband line circuit  7  in the present embodiment can be configured as an LPF card and a broadband line card respectively, or integrated in one broadband line card. The line capturing relay can be arranged in LPF card  5  or in broadband line card  7  as long as it is connected in series between a high pass filter and a low pass filter or is directly connected in series with the subscriber external line connected to the subscriber line. 
   In the present embodiment, the test module  25  is set in the CO broadband device  14 , and is connected to the master control module  16  of the CO broadband device  14  and all the line capturing relays, respectively. The line capturing relay captures the designated subscriber external line according to the line capturing command from the master control  16  and switches the captured line to the line test module  25 . The line test module  25  receives a test command of the master control module  16 , tests the captured subscriber external line and reports the obtained test result to the master control module  16 . 
   The line capturing relay of the present embodiment can be configured in the LPF card or in the broadband line card or in a broadband line card integrating the LPF circuit  5  and the broadband line circuit  7 . The broadband line card of the present embodiment which contains line capturing relays will be described in more detail hereinafter. 
   Refer to  FIG. 8   a , which is a schematic diagram illustrating a first kind of structure and connection of the broadband line card containing line capturing relays in accordance with the embodiment shown in  FIG. 7 . The broadband line card containing line capturing relays as shown in  FIG. 8   a  is applicable in the situation when the broadband line circuit and LPF circuit are configured in a broadband line card and an LPF card, respectively. 
   As shown in  FIG. 8   a , the line capturing relay  12  is configured inside the broadband line card  7 , each subscriber line is configured with a set of line capturing relays  12  which are located between the interface of cable  4  connected to the LPF card  5  and a HPF and an xDSL processing circuit  10 , namely between a low pass filter circuit and a high pass filter circuit of each subscriber line. There is no relay configured inside the LPF card  5  so that the complexity of the LPF card  5  is reduced, and there is no other active electrical circuit or device comprised in the internal circuit of LPF card  5 , thus LPF card  5  is a passive circuit card board. As a result, all LPF cards  5  can be separately set in a passive frame so that the CO broadband device  14  can afford slots and ports for further capacity expansion. 
   Refer to  FIG. 8   b , which is a schematic diagram illustrating a second kind of structure and the connection of broadband line card with line capturing relays in accordance with the embodiment shown in  FIG. 7 . The broadband line card with line capturing relays shown in  FIG. 8   b  is applicable in the situation when the broadband line circuit and the LPF circuit are configured in a broadband line card and an LPF card, respectively. 
   As shown in  FIG. 8   b , line capturing relay  12  is configured inside the broadband line card  7  and is located between the interface of cable  3  and the HPF and xDSL processing circuit  10 , namely between a low pass filter circuit and a distribution frame. Likewise, there is no relay configured inside LPF card  5  so that the complexity of LPF card  5  is reduced, and there is no other active electrical circuit or device comprised in the internal circuit of the LPF card  5 , thus the LPF card  5  is a passive circuit card board. Likewise, all LPF cards  5  can be configured in a separate passive frame so that the CO broadband device  14  can afford slots and ports for further capacity expansion. 
   Refer to  FIG. 8   c , which is a schematic diagram illustrating a third kind of structure and connection of the broadband line card with line capturing relays in accordance with the embodiment shown in  FIG. 7 . The broadband line card with line capturing relays shown in  FIG. 8   c  is applicable in the situation when both the broadband line circuit and the LPF circuit are configured in a broadband line card. 
   As shown in  FIG. 8   c , the LPF circuit  11  and the line capturing relay  12  are both configured inside the broadband line card  7 ; the line capturing relay  12  is connected in series between the LPF circuit  11  and the HPF and the xDSL processing circuit  10 , namely between a low pass filter circuit and a high pass filter circuit. In this way, there is no need to configure an LPF card, making full use of slots and ports of the CO broadband device  14  and saving corresponding electric cables, and accordingly, reducing the complexity of the CO broadband device  14 . 
   Refer to  FIG. 8   d , which is a schematic diagram illustrating a fourth kind of structure and the connection of the broadband line card with line capturing relays in accordance with the embodiment shown in  FIG. 7 . The broadband line card with line capturing relays shown in  FIG. 8   d  is applicable in the situation when both the broadband line circuit and the LPF circuit are configured in a broadband line card. 
   As shown in  FIG. 8   d , the LPF circuit  11  and the line capturing relay  12  are both set inside the broadband line card  7 ; the subscriber external line is connected to the LPF circuit  11  and the HPF and the xDSL processing circuit  10  via the line capturing relay  12 , namely between a low pass filter circuit and a distribution frame. Same as the structure shown in  FIG. 8   c , there is no need to configure an LPF card so as to make full use of slots and ports of the CO broadband device  14 , save corresponding electric cables, and accordingly, reduce the complexity of CO broadband device  14 . 
   Refer to  FIG. 8   e , which is a schematic diagram illustrating a fifth kind of structure and the connection of the broadband line card with line capturing relays in accordance with the embodiment shown in  FIG. 7 . The broadband line card with line capturing relays shown in  FIG. 8   e  is applicable in the situation when both the broadband line circuit and the LPF circuit are configured in a broadband line card. The connection mode of  FIG. 8   e  is similar to that of  FIG. 8   d , except that the LPF circuit  11  is connected with a constantly closed contactor of the line capturing relay. As the principle and advantage is the same as those as shown in  FIG. 8   d , no further description is given here. 
   Preferred Embodiment 3 
   Refer to  FIG. 9 , which is a schematic diagram illustrating the structure of a broadband/narrowband telecommunication system according to a preferred embodiment 3 of the present invention. This embodiment is an embodiment of the second broadband/narrowband telecommunication system provided by the present invention, the system comprising CPEs  1 ˜n, a CO broadband device  14 , a CO narrowband device  13  and a line capturing matrix device  24 . The CO broadband device comprises an LPF card  51 , an LPF card  52 , a broadband line card  71 , a broadband line card  72 , a master control module  16  and a line test module  25 . The CO narrowband device  13  comprises a CO narrowband line card, a master control module and a narrowband service processing module. 
   The subscriber external lines  1  of CPEs  1 ˜m are connected to the LPF card  51  of the CO broadband device  14  through a MDF  151  and the line capturing matrix device  24 , wherein the LPF card  51  is connected to the broadband line card  71  without a line capturing relay, and this group of lines are connected to the CO narrowband device  13  through the MDF  151  and the line capturing matrix device  24 . 
   The subscriber external lines  1  of CPE m+1˜m are directly connected to the LPF card  52  of the CO broadband device  14  through a MDF  152 , the LPF card  52  is connected to the broadband line card with the line capturing relay  72 , and this group of lines are directly connected to the CO narrowband device  13  through the MDF  152 . 
   Test module  25  of the present embodiment is also configured in the CO broadband device  14  and is connected to the line capturing matrix device  24  and the master control module  16  of the CO broadband device  14 , respectively. When testing subscriber external lines of CPEs  1 ˜m, the line test module  25  receives a test command from the master control module  16 , instructs the line capturing matrix device  24  to act according to the command, and then the line capturing matrix device  24  captures the designated subscriber external line according to the instruction and switches the captured line to line test module  25 ; when testing subscriber external lines of CPEs m+1˜n, the broadband line card  72  with line capturing relays captures the designated external line according to the line capturing command from master control module  16  and then switches the line to line test module  25 . 
   The line test module  25  tests the captured subscriber external line and reports a test result obtained to the master control module  16 . 
   In the present embodiment, an interface between the line test module  25  and the line capturing matrix device  24  is the same as that in embodiment 1, and no further description is needed to be given here. The line test module  25  and the broadband line card  72  with line capturing relays are connected through a test bus; and the line test module  25  tests the subscriber external line captured by the broadband line card  72  with line capturing relays via the test bus. 
   The broadband line card  72  with line capturing relays used in the present embodiment can be of any broadband line card with line capturing relays as shown in  FIG. 8   a ˜ 8   e.    
     FIG. 10  is the flowchart of the test in the embodiment as shown in  FIG. 9 . The specific test procedure is as follows: 
   Step  10 : the master control module of the CO broadband device receiving an external test command. 
   The test command may comprise: parameters as the subscriber external line to be tested and what kind of test is to be conducted. 
   Step  20 : according to the command, the master control module judging whether it is a subscriber external line of CPEs  1 ˜m or a line of CPEs m+1˜n which is to be tested; if it is a subscriber external line of CPEs  1 ˜m, proceeding to step  50 , and if it is a subscriber external line of CPEs m+1˜n, proceeding to step  30 . 
   Step  30 : the master control module instructing the broadband line card with line capturing relays to capture a line. 
   Step  40 : the line capturing relay capturing the designated subscriber external line, and making this designated external line physically connected to a test bus in short-circuit, and then proceeding to step  70 . 
   Step  50 : forwarding the command through the communication interface between the line test module and the line capturing matrix device, and instructing the line capturing matrix device to act accordingly. 
   Step  60 : the line capturing matrix device capturing the designated subscriber external line, and making this designated external line physically connected to the test bus in short-circuit. 
   After finishing capturing the subscriber external line, the line capturing matrix device further reporting to the line test module through communication interface that the line capturing operation is completed. 
   Step  70 : the line test module starting to test the subscriber line through the test bus. The processing procedure of the subscriber line signal performed by the test module is the same as in the prior art. 
   Step  80 : after finishing testing the subscriber line, the line test module reporting a result to the master control module for processing. 
   Depending on the need of the test, the test result can also be outputted by the master control module. 
   Functions of the line test module are the same as in Embodiment 1, and no further description is needed to be given here. 
   In the present embodiment, the broadband line card  72  with line capturing relays comprises line capturing relays  12  of each subscriber line, a High Pass Filter (HPF) circuit and a broadband service processing circuit (ATU-C), while the LPF card  52  comprises low pass filters of each subscriber line. The line capturing relay of each subscriber line is connected in series to its corresponding subscriber line, for instance, the line capturing relay can be configured between the high pass filter circuit and the low pass filter of its subscriber line in LPF card  52 , or be configured between the low pass filter and the distribution frame. 
   The present invention is applicable not only to a telecommunication service system in which CO DSLAM and narrowband switching device are separately configured, but also to a telecommunication system in which the two devices are configured in an integrated way. 
   The foregoing description is specific preferred embodiments of the present invention and should not be construed as limiting the protection scope of this invention. It will be understood by those skilled in the art that various changes and substitutions within the technical scope of this invention should be covered by the protection scope of this invention.