JP3092840B2 - Subscriber line test monitoring method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber line multiplex transmission system, that is, a subscriber interface device in which each subscriber terminal includes a plurality of subscriber circuits corresponding to the subscriber terminal via a subscriber line. The subscriber interface once accommodated in a switching center via an optical fiber cable for uplink / downlink multiplex transmission provided commonly to each subscriber terminal. The present invention relates to a subscriber line test monitoring method in an apparatus and the apparatus.

[0002]

2. Description of the Related Art In recent years, as a part of infrastructure development of a communication network using an optical fiber cable, as shown in FIG. 4, a subscriber interface device 3 is separately installed from a switching center building 4 to a remote place such as a user building. In addition, each of the subscriber terminals 1 is temporarily housed in the subscriber interface device 3 via a subscriber line (metallic subscriber line) 2, and furthermore, an optical fiber cable 1 for uplink / downlink multiplex transmission.
A configuration in which the terminal is housed in the exchange office building 4 through the number 0 is adopted. In the subscriber interface device 3, a subscriber circuit (only one subscriber circuit is shown for simplification of the drawing) 30 is provided for the subscriber terminal 1, and subscriber multiplexing from each subscriber circuit 30 is performed. Digital upstream voice signal 50, subscriber multiplex digital subscriber status monitoring signal 51
Is further multiplexed by the demultiplexing circuit 31 together with the test monitoring result 34 on the subscriber line to be tested, which is separately obtained from the subscriber line test monitoring device 32, and is transmitted through the optical fiber cable for uplink multiplex transmission. A signal transmitted to the switching center 4 and transmitted from the switching center 4 via the optical fiber cable for downlink multiplex transmission is demultiplexed by a demultiplexing circuit 31, and is subsequently separated and distributed to each of the subscriber circuits 30. It is separated into a multiplexed digital downstream voice signal 52, a subscriber multiplexed digital subscriber circuit control signal 53, and a subscriber line test monitoring control signal (not shown) to the subscriber line test monitoring device 32. .

[0003] Each of the subscriber circuits 30 terminates a subscriber line (consisting of a subscriber terminal 1 and a subscriber line 2), and converts an upstream two-line audio signal from this subscriber line into a four-line audio signal. At the same time, the two-line four-line converter 30 converts the four-line audio signal to the subscriber line into a two-line audio signal.
1, the analog upstream audio signal 500 is converted into a digital signal, and the compressed PCM is compressed in accordance with the μ-law rule companding rule.
The encoder 302 for converting the signal into a signal, and the subscriber downstream multiplexed digital downstream voice signal 52 from the demultiplexer 31 converts the digital downstream voice signal (compressed PCM signal) to the subscriber circuit into a μ-law companding rule. And a decoder 303 for converting the signal into an analog downstream audio signal 520. Although not shown, each of the compressed PCM signal from each of the subscriber circuits 30 and the digital subscriber state monitoring signal (including the state change information of the DC loop current due to the on / off hook state change in the subscriber terminal 1) is provided. By being multiplexed by the subscriber, the demultiplexing circuit 3
1 and a subscriber multiplex digital upstream voice signal 50 and a subscriber multiplex digital subscriber status monitor signal 51 are obtained. Conversely, the subscriber multiplex digital subscriber circuit control signal 53 from the demultiplexing circuit 31 is separated on the subscriber circuit 30 side in accordance with the subscriber circuit 30, and is controlled by the separated digital subscriber circuit control signal. Each of the subscriber circuits 30 is controlled from the switching center 4 as desired.

By the way, various tests / measurements / monitoring (detection of short-circuit / open, detection of ON / OFF-hook state, detection of line capacity / ground) In order to perform measurement of line capacity / line voltage, dial pulse (DP) waveform monitoring test, busy subscriber monitoring test, and the like, the subscriber line is connected to the subscriber line test pull-in circuit 300 in the corresponding subscriber circuit 30. , Subscriber line test monitoring device 3 via subscriber line test drop-in line 33
2 is selectively drawn in. When a digital subscriber's circuit control signal from the switching center 4 instructs a particular subscriber's circuit 30 to drop in a test, the subscriber's line test drop-in circuit 300 in that subscriber's circuit 30 is sent.
In the state where the subscriber line as a test target is pulled into the subscriber line test monitoring device 32, various tests / measurements /
Monitoring is performed in an analog manner.

For example, when a dial pulse (DP) waveform monitoring test is performed, a subscriber line to be tested is pulled into a dial pulse monitoring circuit 320 in a subscriber line test monitoring device 32 and a DP type subscription is performed. Terminal 1
Dial signal counting and make rate (make rate: the time ratio of dial pulse contact (make) and break (break)) by processing the DP signal from
Is detected, and the counting / detection result is obtained as the analog test monitoring result 34. In addition, a busy subscriber monitoring test (this test is performed, for example, by a third party to check whether the called subscriber terminal is in a busy state for a long time, but is actually in a busy state. Is performed when the maintenance person has a request to do so), the subscriber line to be tested is pulled into the busy subscriber monitoring circuit 321 in the subscriber line test monitoring device 32. In this state, the presence or absence of the voice signal is detected, and the detection result is obtained as the analog test monitoring result 34. The normality of the two-party call can be confirmed by the busy subscriber monitoring test. In addition, as for the related art related to the subscriber system test method,
For example, "Maintenance test method for digital subscriber line exchange"
(NTT Research and Application Report Vol. 31 No. 11 (198
2) P2017 to 2029) are known.

[0006]

In the case of a subscriber interface device which is separately installed from a switching center, it is considered that the number of subscribers accommodated in the device will decrease in the future as the use of optical fiber transmission lines progresses. However, the cost / space per subscriber required for the subscriber line test monitoring device provided in the subscriber interface device is expected to increase conversely. is there. In particular, if the hardware scale of each of the above-described dial pulse monitoring circuit and busy subscriber monitoring circuit is large, the cost / space required for the subscriber line test monitoring apparatus, and therefore the subscriber interface apparatus, is correspondingly large. For this reason, the subscriber line test monitoring apparatus has been cited as one of the major obstacles to economical realization of the subscriber interface apparatus. An object of the present invention is to test and monitor a subscriber line while reducing the cost / space per subscriber by digitally performing a part of various tests / measurements / monitorings which have been performed analogously. The present invention provides a subscriber line test monitoring method and apparatus which can be used.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is basically based on a subscriber multiplex digital subscriber circuit control signal and a subscriber terminal placed under test monitoring and a subscriber line corresponding to the subscriber terminal. The subscriber line is selectively led to the subscriber line test monitoring side via the corresponding subscriber circuit, and the analog test monitoring result is obtained by various analog test monitoring. When a subscriber line to be tested and monitored is specified from the result of monitoring the control state of each of the subscriber circuits from the circuit control signal, a digital upstream voice signal relating to the subscriber line, a digital subscriber state monitoring. Signal and digital downstream voice signal are subscriber multiplex digital upstream voice signal, subscriber multiplex digital subscriber status monitor signal, subscriber multiplex digital downstream In a state of being extracted from the voice signal, respectively, it is achieved by obtaining a digital test monitoring results by digitally testing monitors for subscriber lines as test monitored. Also, based on the subscriber multiplex digital subscriber circuit control signal, a subscriber line comprising a subscriber terminal to be monitored and monitored and a subscriber line corresponding to the subscriber terminal is selectively pulled in via the corresponding subscriber circuit. Up,
An analog test monitoring unit that performs various test monitoring in an analog manner and obtains an analog test monitoring result, and a monitoring status of a control state for each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, as a test monitoring target. When the subscriber line is specified, the digital upstream voice signal, the digital subscriber status monitor signal and the digital downstream voice signal relating to the subscriber line are converted into the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor. signal,
This is achieved by at least comprising a digital test monitoring unit that performs test monitoring of a subscriber line as a test monitoring target by digital processing in a state extracted from each of the subscriber multiplexed digital downstream voice signals.

[0008]

In a test / measurement / monitoring item for a subscriber line as a test / monitoring target, at least a digital upstream voice signal, a digital subscriber state monitoring signal, and a digital downstream voice signal relating to the subscriber line; Specifically, at least the dial pulse waveform monitoring test and the busy subscriber monitoring test are to be performed digitally. When test monitoring is performed digitally, the processing circuit itself can be highly integrated, which is advantageous in terms of the number of components, circuit scale, power consumption, and the like, as compared with the case where analog processing is performed. Is what is being done.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. First, a subscriber line test monitoring device according to the present invention will be described. FIG. 1 shows a configuration of an example of a subscriber interface device including the subscriber line test monitoring device. As shown, what is substantially different from that shown in FIG. 4 is that the subscriber multiplex digital upstream voice signal 50 transmitted and received between each of the subscriber circuits 30 and the demultiplexer circuit 31, the subscriber multiplex digital subscriber status. Monitoring signal 51,
The subscriber multiplex digital down voice signal 52 and the subscriber multiplex digital subscriber circuit control signal 53 are drawn into the subscriber line test monitor 32, and the digital upstream voice signal and digital Digital test monitoring is performed with the subscriber status monitor signal and the digital downstream voice signal extracted from the subscriber multiplex digital upstream voice signal, the subscriber multiplex digital subscriber status monitor signal, and the subscriber multiplex digital downstream voice signal, respectively. By doing so, at least digital test monitoring results for each of the dial pulse waveform monitoring test and the busy subscriber monitoring test can be obtained. Analog test monitoring results have been obtained by analog test monitoring, except for the dial pulse waveform monitoring test and busy subscriber monitoring test, as before, but these digital test monitoring results and analog test monitoring The monitoring result is the analog / digital test monitoring result 34
, And together with the subscriber multiplex digital upstream voice signal 50 and the subscriber multiplex digital subscriber status monitor signal 51 from each of the subscriber circuits 30,
1 and transmitted to the switching center 4 via an optical fiber cable for upstream multiplex transmission.

Here, digital test monitoring will be described in detail as follows. That is, the subscriber multiplexed digital subscriber circuit control signal 53 is passed through the control signal receiving section 324 to the control state determination section 325, where
The control status of each of them is constantly monitored. From the monitoring results, a subscriber line as a test monitoring target can be easily specified. When a subscriber line to be monitored is specified, the digital upstream voice signal, the digital subscriber status monitoring signal, and the digital downstream voice signal related to the subscriber line are subscriber multiplexed by the voice / monitoring signal receiving unit 322. Digital upstream audio signal 50,
After being extracted from each of the subscriber multiplex digital subscriber status monitor signal 51 and the subscriber multiplex digital downstream voice signal 52 and digitally processed by the voice / monitor signal processor 323, the digital signal of the subscriber line is obtained. Test monitoring results have been obtained.

FIG. 2 shows a functional block configuration of an example of the voice / monitoring signal processing unit 323 when a dial pulse waveform monitoring test is performed. As shown, a dial pulse digital detection circuit 3230 including a loop change detection circuit 60 and a loop change time detection circuit 61 inside the voice / monitoring signal processing unit 323.
Is provided. In the dial pulse digital detection circuit 3230, the voice / monitoring signal receiving unit 32
The digital subscriber status signal relating to the subscriber line as the test monitoring object extracted from the digital subscriber line 2 is digitally processed. More specifically, the loop change detection circuit 6
At 0, the state change of the DC loop current in the digital subscriber state monitoring signal is monitored, and the dial number is identified by determining the number of make and break of the dial pulse. The change time detecting circuit 61 also monitors the state change time of the DC loop current in the digital subscriber state monitor signal so as to confirm the normality of the dial pulse make and break times. The rate has been detected.

FIG. 3 shows an example of the functional block configuration of the voice / monitoring signal processing unit 323 when a busy subscriber monitoring test is performed. As shown, the audio / monitoring signal processing unit 323 has a μ-law decompression conversion unit 70, a digital audio addition unit 71, and a μ-l
The digital audio adding circuit 3231 including the aw compression conversion processing section 72 is provided. The digital voice addition circuit 3231 includes a voice / monitoring signal receiving unit 322
The digital upstream audio signal and the digital downstream audio signal relating to the subscriber line as the test monitoring object extracted from the above are digitally processed. More specifically, the digital upstream audio signal and the digital downstream audio signal are each subjected to μ-law expansion conversion processing by the μ-law expansion conversion section 70 to obtain a linear value, and then added by the digital audio addition section 71. Thereafter, the μ-law compression conversion processing section 72 performs the μ-law compression conversion processing again, thereby obtaining a non-linear value. This is transmitted to the switching center 4 as a digital test monitoring result. However, the digital voice addition circuit 3231 may be configured as a processor. In addition, it is possible to digitally monitor a call from the subscriber terminal 1 by pulling in only the digital upstream voice signal and a call monitoring from the other party by pulling in only the digital downstream voice signal.

[0013]

As described above, according to the first and second aspects of the present invention, a part of various tests / measurements / monitorings which have been performed in an analog manner is performed digitally so that one subscriber can be used. A subscriber line test monitoring method and apparatus capable of testing and monitoring a subscriber line with a reduced cost / space per unit, and a dial which has been performed analogously until now according to the third and fourth embodiments. A subscriber line test monitoring method and apparatus capable of performing test monitoring of a subscriber line with a reduced cost / space per subscriber by digitally performing a pulse waveform monitoring test. According to, by performing a busy subscriber monitoring test that was previously performed in analog, by digital,
A subscriber line test monitoring method and apparatus capable of testing and monitoring a subscriber line with reduced cost / space per subscriber can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of a subscriber interface device including a subscriber line test monitoring device according to the present invention;

FIG. 2 is a diagram showing a functional block configuration of an example of a voice / monitoring signal processing unit when a dial pulse waveform monitoring test is performed;

FIG. 3 is a diagram showing a functional block configuration of an example of a voice / monitoring signal processing unit when a busy subscriber monitoring test is performed;

FIG. 4 is a diagram for explaining a subscriber line test monitoring method according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Subscriber terminal, 10 ... Optical fiber cable, 3 ... Subscriber interface device, 30 ... Subscriber circuit, 300 ...
Subscriber line test drop-in circuit, 301... 2-wire 4-wire converter,
302 encoder, 303 decoder, 31 demultiplexing circuit, 32 subscriber line test monitoring device, 322 voice / monitoring signal receiving unit, 323 voice / monitoring signal processing unit, 323
0: dial pulse digital detection circuit, 3231: digital voice addition circuit, 324: control signal receiving unit, 32
5: control state judgment unit, 33: subscriber line test drop-in line,
4 ... switching office building, 50 ... subscriber multiplex digital uplink voice signal, 51 ... subscriber multiplex digital subscriber status monitor signal,
52: subscriber multiplexed digital downstream voice signal; 53: subscriber multiplexed digital subscriber circuit control signal; 60: loop change detection circuit; 61: loop change time detection circuit;
-Law decompression converter, 71 ... digital voice adder, 7
2 μ-law compression converter

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuhiro Fukunari 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Within the Information and Communication Division, Hitachi, Ltd. No. 6 Inside Nippon Telegraph and Telephone Corporation (72) Yoshitaka Ishihama, inventor Nippon Telegraph and Telephone Corporation, 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo (56) Reference JP-A-3-151750 (JP, A) (58 ) Surveyed field (Int.Cl. ⁷ , DB name) H04M 3/22 H04M 19/02

Claims (6)

(57) [Claims] 1. Externally, each subscriber terminal is accommodated via a subscriber line corresponding to the subscriber terminal in a state where the subscriber terminal is separately installed at a remote place from the exchange building. On the other hand, internally, the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor signal from each of the subscriber circuits corresponding to the subscriber terminals are accommodated via the optical fiber cable for downlink / multiplex transmission. Along with the separately obtained analog / digital test monitoring result for the subscriber line to be tested, the signal is transmitted to the switching center via the multiplexing optical fiber cable via the multiplexing circuit, and is transmitted from the switching center to the downstream. Optical fiber cable for multiplex transmission
The signal transmitted via the receiver is transmitted through a demultiplexer to a subscriber multiplexed digital downstream voice signal and a subscriber multiplexed digital subscriber circuit control signal which are later separated and distributed to each of the subscriber circuits. A subscriber line test monitoring method in a subscriber interface device separated from a subscriber line test monitoring control signal, wherein the subscriber terminal is placed in a test monitoring target based on a subscriber multiplex digital subscriber circuit control signal. The subscriber line composed of the subscriber line corresponding to the subscriber terminal is selectively drawn into the subscriber line test monitoring side through the corresponding subscriber circuit, and the analog test monitoring result is obtained by various analog test monitoring. On the other hand, from the result of monitoring the control state of each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, a test monitor If the subscriber line is identified as a digital uplink speech signal according to said subscriber line,
The digital subscriber status monitor signal and the digital downstream voice signal are extracted from the subscriber multiplex digital upstream voice signal, the subscriber multiplex digital subscriber status monitor signal, and the subscriber multiplex digital downstream voice signal. A subscriber line test / monitoring method wherein a digital test / monitoring result is obtained by digital test / monitoring of a subscriber line. 2. Externally, each of the subscriber terminals is accommodated via a subscriber line corresponding to the subscriber terminal in a state where the subscriber terminals are separately installed at a remote place from the switching center, and the subscriber terminal is connected to the switching center. On the other hand, internally, the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor signal from each of the subscriber circuits corresponding to the subscriber terminals are accommodated via the optical fiber cable for downlink / multiplex transmission. Along with the separately obtained analog / digital test monitoring result for the subscriber line to be tested, the signal is transmitted to the switching center via the multiplexing optical fiber cable via the multiplexing circuit, and is transmitted from the switching center to the downstream. Optical fiber cable for multiplex transmission
The signal transmitted via the receiver is transmitted through a demultiplexer to a subscriber multiplexed digital downstream voice signal and a subscriber multiplexed digital subscriber circuit control signal which are later separated and distributed to each of the subscriber circuits. A subscriber line test monitoring device in a subscriber interface device separated into a subscriber line test monitoring control signal, the subscriber terminal being set as a test monitoring target based on a subscriber multiplex digital subscriber circuit control signal. An analog test monitoring unit for selectively drawing in a subscriber line composed of the subscriber line corresponding to the subscriber terminal via the corresponding subscriber circuit, and performing various test monitoring in an analog manner to obtain an analog test monitoring result; From the result of monitoring the control status of each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, the subscriber Is specified, the digital upstream voice signal, the digital subscriber status monitoring signal, and the digital downstream voice signal for the subscriber line are converted into a subscriber multiplex digital upstream voice signal, a subscriber multiplex digital subscriber status monitoring signal, A digital test monitoring unit for performing digital monitoring of test monitoring of a subscriber line as a test monitoring target in a state extracted from each of the user multiplexed digital downlink audio signals. 3. Externally, each of the subscriber terminals is accommodated via a subscriber line corresponding to the subscriber terminal in a state where the subscriber terminals are separately installed at a remote place from the switching center, and the subscriber terminal is connected to the switching center. On the other hand, internally, the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor signal from each of the subscriber circuits corresponding to the subscriber terminals are accommodated via the optical fiber cable for downlink / multiplex transmission. Along with the separately obtained analog / digital test monitoring result for the subscriber line to be tested, the signal is transmitted to the switching center via the multiplexing optical fiber cable via the multiplexing circuit, and is transmitted from the switching center to the downstream. Optical fiber cable for multiplex transmission
The signal transmitted via the receiver is transmitted through a demultiplexer to a subscriber multiplexed digital downstream voice signal and a subscriber multiplexed digital subscriber circuit control signal which are later separated and distributed to each of the subscriber circuits. A subscriber line test monitoring method in a subscriber interface device separated from a subscriber line test monitoring control signal, wherein the subscriber terminal is placed in a test monitoring target based on a subscriber multiplex digital subscriber circuit control signal. The subscriber line composed of the subscriber line corresponding to the subscriber terminal is selectively drawn into the subscriber line test monitoring side through the corresponding subscriber circuit, and the analog test monitoring result is obtained by various analog test monitoring. On the other hand, from the result of monitoring the control state of each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, a test monitor If the subscriber line is specified as, the digital subscriber status monitoring signal for the subscriber line is extracted from the subscriber multiplex digital subscriber status monitoring signal, and the status change and the status continuation of the signal are continued. A subscriber line test monitoring method in which the time is digitally measured so that the dial pulse count and make rate can be obtained as digital test monitoring results. 4. Externally, each of the subscriber terminals is accommodated via a subscriber line corresponding to the subscriber terminal in a state where the subscriber terminals are separately installed at a remote place from the switching center, and the subscriber terminal is connected to the switching center. On the other hand, internally, the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor signal from each of the subscriber circuits corresponding to the subscriber terminals are accommodated via the optical fiber cable for downlink / multiplex transmission. Along with the separately obtained analog / digital test monitoring result for the subscriber line to be tested, the signal is transmitted to the switching center via the multiplexing optical fiber cable via the multiplexing circuit, and is transmitted from the switching center to the downstream. Optical fiber cable for multiplex transmission
The signal transmitted via the receiver is transmitted through a demultiplexer to a subscriber multiplexed digital downstream voice signal and a subscriber multiplexed digital subscriber circuit control signal which are later separated and distributed to each of the subscriber circuits. A subscriber line test monitoring device in a subscriber interface device separated into a subscriber line test monitoring control signal, the subscriber terminal being set as a test monitoring target based on a subscriber multiplex digital subscriber circuit control signal. An analog test monitoring unit for selectively drawing in a subscriber line composed of the subscriber line corresponding to the subscriber terminal via the corresponding subscriber circuit, and performing various test monitoring in an analog manner to obtain an analog test monitoring result; From the result of monitoring the control status of each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, the subscriber Is specified, the state change and the state duration of the digital subscriber state monitor signal relating to the subscriber line are digitally measured with the digital subscriber state monitor signal extracted from the subscriber multiplex digital subscriber state monitor signal. A digital test monitoring unit for obtaining a dial pulse count and a make rate from the result as a digital test monitoring result. 5. Externally, each of the subscriber terminals is accommodated via a subscriber line corresponding to the subscriber terminal in a state where the subscriber terminals are separately installed at a remote place from the exchange building. On the other hand, internally, the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor signal from each of the subscriber circuits corresponding to the subscriber terminals are accommodated via the optical fiber cable for downlink / multiplex transmission. Along with the separately obtained analog / digital test monitoring result for the subscriber line to be tested, the signal is transmitted to the switching center via the multiplexing optical fiber cable via the multiplexing circuit, and is transmitted from the switching center to the downstream. Optical fiber cable for multiplex transmission
The signal transmitted via the receiver is transmitted through a demultiplexer to a subscriber multiplexed digital downstream voice signal and a subscriber multiplexed digital subscriber circuit control signal which are later separated and distributed to each of the subscriber circuits. A subscriber line test monitoring method in a subscriber interface device separated from a subscriber line test monitoring control signal, wherein the subscriber terminal is placed in a test monitoring target based on a subscriber multiplex digital subscriber circuit control signal. The subscriber line composed of the subscriber line corresponding to the subscriber terminal is selectively drawn into the subscriber line test monitoring side through the corresponding subscriber circuit, and the analog test monitoring result is obtained by various analog test monitoring. On the other hand, from the result of monitoring the control state of each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, a test monitor When the subscriber line is specified as, the digital upstream voice signal and the digital downstream voice signal relating to the subscriber line are extracted from the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital downstream voice signal, respectively. And the result of the addition is obtained as a digital test monitoring result. 6. Externally, each of the subscriber terminals is accommodated via a subscriber line corresponding to the subscriber terminal in a state where the subscriber terminals are separately installed at a remote place from the switching center building, and the subscriber station is connected to the switching center building. On the other hand, internally, the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital subscriber status monitor signal from each of the subscriber circuits corresponding to the subscriber terminals are accommodated via the optical fiber cable for downlink / multiplex transmission. Along with the separately obtained analog / digital test monitoring result for the subscriber line to be tested, the signal is transmitted to the switching center via the multiplexing optical fiber cable via the multiplexing circuit, and is transmitted from the switching center to the downstream. Optical fiber cable for multiplex transmission
The signal transmitted via the receiver is transmitted through a demultiplexer to a subscriber multiplexed digital downstream voice signal and a subscriber multiplexed digital subscriber circuit control signal which are later separated and distributed to each of the subscriber circuits. A subscriber line test monitoring device in a subscriber interface device separated into a subscriber line test monitoring control signal, the subscriber terminal being set as a test monitoring target based on a subscriber multiplex digital subscriber circuit control signal. An analog test monitoring unit for selectively drawing in a subscriber line composed of the subscriber line corresponding to the subscriber terminal via the corresponding subscriber circuit, and performing various test monitoring in an analog manner to obtain an analog test monitoring result; From the result of monitoring the control status of each subscriber circuit from the subscriber multiplex digital subscriber circuit control signal, the subscriber Is specified, the digital upstream voice signal and the digital downstream voice signal related to the subscriber line are extracted from the subscriber multiplex digital upstream voice signal and the subscriber multiplex digital downstream voice signal, respectively, and added. And a digital test monitoring unit that obtains the result of the digital test monitoring as a digital test monitoring result.