JPH04277964A - Subscriber line loss measuring system - Google Patents

Abstract

PURPOSE:To measure subscriber line loss under the control of a station in the line loss measuring system of a two-wire digital subscriber line. CONSTITUTION:A two-wire digital subscriber line transmission system capable of connecting a subscriber line 40 by which a station terminating device 10 is connected to a customer termination device 30 to a test circuit 20 via a test bracketing circuit 11 in the station terminating device is comprised by providing a DC superimposing means 21 which sends a DC to the subscriber line when the test bracketing circuit is operated, a polarity inversion means 22 which inverts the polarity of the DC to be sent to the subscriber line when the line loss is measured, and a loss measuring means 23 which measures the level of a signal for measurement to be sent to the subscriber line at the test circuit, and providing a polarity inversion detecting means 31 which sends a control signal when the polarity inversion of the DC on the subscriber line is detected, a switching means 32 which connects the subscriber line to a signal sending means 33 for measurement while receiving the control signal, and the signal sending means 33 for measurement which sends the signal for measurement to the subscriber line via the switching means while receiving the control signal at the customer terminating device.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring line loss in two-wire digital subscriber lines. In a communication network, the loss value for each section is allocated in advance for the loss between the subscriber terminal that communicates and the subscriber terminal. Loss standards for subscriber lines are also established.

[0002] Conventionally, loss standards for subscriber lines have been based on loss values at one or more frequencies within the voice band for analog voice, but in recent years, loss standards for ISD
N (Integrated Service Digital Communication Network) subscriber lines, etc.
With the increase in subscriber lines through which digital signals are transmitted and received,
Loss standards have been established that are compatible with digital signal transmission.

[0003] Two-wire digital subscriber lines utilize the conventional subscriber lines used in telephone lines as they are, and are equipped with office channel units (hereinafter referred to as "office channel units") for digital transmission at both ends of the subscriber lines. (written as OCU) and in-home terminal equipment (Data Se
rvice unit (hereinafter referred to as DSU) is connected and configured. Loss measurements of subscriber lines are performed when the subscriber line is used as a digital subscriber line, that is, when the OCU and DSU mentioned above are installed, and also when a line failure occurs. Generally, only a value at one specific frequency (for example, 40 kHz) is specified as a loss value.

[0004] Loss measurement of subscriber lines is performed using the above OCU and D.
Measurements are often made between SUs, but in principle a measurement signal of a specified frequency is sent out at a constant level from one end of the subscriber line, and the level of the frequency received at the other end is measured using a level meter. By doing this, the loss value can be obtained. . However, in order to do so, it is necessary to place a measuring person at both ends of the subscriber line, so there is a problem in that the measurement requires time and effort.

[0005]

2. Description of the Related Art FIG. 3 is a diagram showing a method for measuring line loss of a digital subscriber line in the prior art.

[0006] OCU (in-office terminal unit) installed at the office side
Reference numeral 10 is provided to correspond to a subscriber line, and is connected via a subscriber line 40 to a DSU (in-house termination unit) 60 installed inside the premises. A terminal device (not shown) is connected to the DSU 60, and the terminal device performs data communication with a partner terminal device (not shown) via an in-office device (not shown) such as an exchange connected to the OCU 10. .

When measuring the loss of the subscriber line 40, inside the premises, disconnect the point A and point B that connect the subscriber line 40 and the DSU 60, and disconnect the oscillator 7 connected to the point C.
Connect 0 to point A. Note that points A and B are generally terminals of a wiring board in the house or test bullets, and point C is a clip connected to the oscillator 70. Further, a synthesizer is often used as the oscillator 70.

On the other hand, each OCU 10 within the station has multiple OCUs.
(For example, a plurality of OCUs mounted on the same shelf) are configured so that a test can be performed using a test circuit 50 provided in common.
The O under test is controlled by the operation unit (not shown) in the O
The test separation circuit 11 in the CU 10 is operated, and the connection lines to the subscriber line 40 and the in-office equipment are drawn into the test circuit 50, so that the subscriber line 40 side and the in-office equipment side can be separated and tested. It has become.

When measuring the loss of the subscriber line 40, the test disconnection circuit 11 is operated and the subscriber line 40 to be measured is drawn into the test circuit 50.
A level meter 51 provided therein is connected to the subscriber line 40 to be measured. Note that if the level meter 51 is not provided in the test circuit 50 but is provided in common to a plurality of test circuits 50, it is connected to the subscriber line under test via the test disconnection circuit 11. A level meter is connected to a measurement jack or terminal (not shown) in the test circuit 50.

In this state, the loss of the subscriber line 40 to be measured is determined by transmitting a specified measurement frequency at a constant level from the oscillator 70 inside the premises and measuring the reception level with the level meter 51 inside the station. be able to.

[0011]

[Problem to be Solved by the Invention] When measuring the line loss of a two-wire digital subscriber line, in the conventional technology, it is necessary for the measurer to go to the subscriber's premises with an oscillator each time the measurement is made, and it is necessary to Connected subscriber lines and DSUs
There is a problem in that measurement requires a lot of effort because it is necessary to disconnect the connection between the subscriber lines, connect the oscillator, and then reconnect the subscriber line and the DSU after the measurement is completed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a subscriber line loss measuring system that is capable of measuring subscriber line loss under control from the station side.

[0013]

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, 10 is an in-office termination device installed in the office in a two-wire digital subscriber line transmission system;
1 is a test circuit for testing the in-office termination device 10; 30 is an in-home termination device installed in the subscriber's premises; 40 is a subscriber line connecting between the in-office termination device 10 and the in-home termination device 30;
Reference numeral 1 denotes a test disconnection circuit provided in the in-office termination device 10 and connecting the subscriber line 40 to the test circuit 20.

Reference numerals 21 to 23 are provided in the test circuit 20, and 21 is a DC current that sends a DC current to the subscriber line 40 connected through the test separation circuit 11 when the test separation circuit 11 is in operation. A superimposing means 22 is the subscriber line 4
When measuring a line loss of 0, the DC current superimposition means 2
1 to the subscriber line 40; 23 is the subscriber line 40;
loss measuring means for measuring the level of the measurement signal received through the

31 to 33 are provided in the home termination device 30, and 31 monitors the DC current sent to the subscriber line 40, and when it detects a polarity reversal of the DC current, it waits for a certain period of time. , a polarity reversal detection means for transmitting a control signal, 32 is provided between the subscriber line 40 and the terminal device connected to the in-home termination device 30, and the polarity reversal detection means 31 transmits the control signal. switching means 33 connects the subscriber line 40 to the measuring signal sending means 33 while the subscriber line 40 is being sent out from the polarity reversal detecting means 31; This is a measurement signal sending means for sending a measurement signal to the line 40.

[0016]

[Operation] In FIG. 1, when measuring the loss of the subscriber line 40, the station side operates an operation section (not shown) in the test circuit 20 to connect the subscriber line 40 under test to the in-office terminal. The test disconnection circuit 11 in the device 10 is operated to draw the subscriber line 40 under test into the test circuit 20. As a result, a direct current is sent to the subscriber line 40 under test from the direct current superimposing means 21.

Inside the home, the polarity reversal detection means 31 in the home termination device 30 monitors the DC current sent out from the DC current superimposition means 21, but no control signal is sent out with the polarity of the DC current in this state.

Next, in order to measure the loss inside the office, the polarity reversal means 22 is controlled from the operation section to reverse the polarity of the DC current being sent out from the DC current superimposing means 21. 31 detects polarity reversal,
A control signal is sent to the switching means 32 and the measurement signal sending means 33 for a certain period of time.

The switching means 32 connects a subscriber line 40 which is extended to a terminal device (not shown) via the switching means 32.
While receiving the control signal, it is disconnected from the terminal device and connected to the measurement signal sending means 33. Further, while the measurement signal sending means 33 is receiving the control signal from the polarity reversal detection means 31, it generates a measurement signal and sends it to the subscriber line 40 via the switching means 32.

The measurement signal sent to the subscriber line 40 is received by the loss measuring means 23 in the test circuit 20 via the test disconnection circuit 11 in the local termination device 10, and the reception level is measured. Since the transmission level of the measurement signal transmitted from the measurement signal transmission means 33 of the home termination device 30 is determined in advance, the loss of the subscriber line 40 can be obtained by measuring the reception level.

As described above, in the present invention, the measurement signal is sent out from the in-home termination device 30 under control from the station side, so there is no need for the measurer to bring an oscillator for measurement into the premises.

[0022]

Embodiment FIG. 2 is a block diagram of an embodiment of the present invention. The same objects are shown using the same symbols throughout the figures, 10 is the in-office termination unit (hereinafter referred to as OCU), 20 is the test circuit (OCU TST), 30 is the in-home termination unit (hereinafter referred to as DSU), and 21 is the in-house termination unit (hereinafter referred to as DSU). DC current superimposition circuit, 22 is a polarity reversal circuit, 23 is a level meter (LM), 31 is a polarity reversal detection circuit, 31a is a photocoupler, 31b is a differentiating circuit (D), 31c is a timer (TIM), 32 is a switching circuit, 33 is an oscillator (OSC).

[0023] Also, T1, T2, T31, T32 are transformers, R1, R2, R3, R4 are resistors, C1, C2
is a capacitor, D1 is a diode, t1, t2, r1
, r2, m1, m2 are relay contacts, and E is a superimposed DC power supply.

In FIG. 2, the test circuit 20 includes a plurality of OCs.
An OCU that is provided in common with U10 and that performs a test from an operation section (not shown) of the test circuit 20 when performing a test.
The relay T (not shown) of the test disconnection circuit 11 of 10 is operated, and its contacts t1 and t2 are switched to connect the subscriber line 40.
into the test circuit 20. In addition, in this case, the in-office equipment
(Not shown) The subscriber line 40 side is cut out, and a test line for testing the in-office equipment is also drawn in, but the in-office equipment side is not shown in FIG.

When measuring the loss of the subscriber line 40 based on the above premise, by operating the operation section in the test circuit 20, the test disconnection in the local termination device 10 to which the subscriber line 40 under test is connected is detected. Contacts t1, t2 of branch circuit 11
is operated to draw the subscriber line 40 under test into the test circuit 20. As a result, a negative polarity DC current is sent to the subscriber line 40 under test from the DC power supply E of the DC current superimposing circuit 21 via the resistor R1. This DC current passes through the subscriber line 40 and is connected to the resistor R3 and diode D in the DSU 30.
1 returns to resistor R2 and falls to the ground. At this time, since the polarity of the photocoupler 31a of the polarity reversal detection circuit 31 in the DSU 30 is reversed, no current flows.
Output is off.

In this state, when the R relay (not shown) of the polarity reversing circuit 22 is operated from the operation section, its contacts r1 and r2 are switched, so that the DC current being sent to the subscriber line 40 is Polarity is reversed. As a result, current flows through the photocoupler 31a in the DSU 30, turning on the output. The differentiating circuit 31b detects the change of the photocoupler 31a from off to on, and starts the timer 31.
The detection output is sent to c. When the timer 31c receives the detection output from the differentiating circuit 31b, the timer 31c operates for a certain period of time.
A control signal is sent to the switching circuit 32 and the oscillator 33.

In the switching circuit 32, the control signal causes a relay M (not shown) to operate, switching its contacts m1 and m2, and the oscillator 33 outputs a measurement signal having a predetermined measurement frequency and output level. This measurement signal is sent to the test circuit 20 on the station side via the subscriber line 40 and received by the level meter 23. A measurer can know the loss value of the subscriber line 40 by reading the level meter 23. The measurement signal is sent out during a certain period of time when the control signal is output from the timer 31c, but by setting this certain period of time to a time sufficient for the measurer to read the level meter 23, it is possible to interfere with the measurement. It can be done without.

As described above, in the configuration shown in FIG. 2, the measuring signal is transmitted from inside the house under remote control from the office side, so there is no need for the person performing the measurement to bring an oscillator to the house. Although the embodiment of the present invention has been described above with reference to FIG. 2, FIG. 2 merely shows one embodiment of the present invention.
It is easily possible to realize the present invention with a configuration different from that shown in FIG.

For example, in FIG. 2, direct current is sent out from the test circuit 20, but in the case of an OCU that always sends out direct current from inside the OCU 10 to prevent oxidation of electrical contact parts, etc. The polarity inversion circuit 22 is connected to OCU.
10, and this OC is controlled by the test circuit 20.
The effects of the present invention can also be obtained by operating the polarity inversion circuit in U10. However, in this case, it is necessary to provide a polarity reversal circuit for each OCU, so a polarity reversal circuit is provided in a test circuit 20 that is commonly provided to multiple OCUs 10.
The number of polarity inverting circuits is larger than in the example shown in FIG.

Furthermore, in the DC current superimposition circuit 21 of FIG. 2, the transformer T2 is used to superimpose the DC current, but there are various known methods for superimposing a DC current on the communication line, and the present invention Of course, the circuit is not limited to the circuit shown in FIG.

In FIG. 2, the level meter 23 is connected to the test circuit 2.
Although an example is shown in which the level meter 23 is installed in the test circuit 20, one set of test circuits 20 is provided for each of a plurality of OCUs, and in a system that assumes that multiple sets of test circuits 20 are installed, the level meter 23 is It may not be provided for each test circuit. In this case, it is clear that the same effect as in FIG. 2 can be obtained by providing a jack or terminal for connecting a level meter in the test circuit 20 and connecting an external level meter to this. In addition, in FIG. 2, the level meter 23 is connected to the secondary side of the transformer T2 of the DC current superimposing circuit 21, but the connection point of the level meter 23 is not limited to the position shown in FIG. Of course, the same effect can be obtained even if the connection is made closer to the line 40, for example, to the input section of the test circuit 20.

Furthermore, although the internal circuit of the DSU 30 in FIG. 2 is shown as a 2-wire system, in the case of a DSU that performs 2-wire/4-wire conversion internally and is connected to a terminal device through 4-wires,
It is clear that the effects of the present invention can be obtained by providing the switching circuit 32 and the OSC 33 in the transmission circuit to the OCU of the 4-wire section.

Note that the OSC 33 is not limited to a sine wave; for example, the OSC 33 may generate a unipolar pulse, convert it into a bipolar pulse in a transmission circuit (not shown), and send it to the subscriber line 40. (
In this case, the conversion of losses measured with bipolar pulses and losses measured with sine waves is known).

[0034]

[Effects of the Invention] As explained above, according to the present invention,
When measuring the line loss of a two-wire digital subscriber line, the measurement signal is sent from inside the premises under remote control from the station side, so there is no need for the person measuring to go into the premises with an oscillator, The efficiency of subscriber line loss measurement can be significantly improved.

[Brief explanation of the drawing]

[Figure 1] Diagram explaining the principle of the present invention

[Figure 2] Embodiment configuration diagram of the present invention

[Figure 3] Block diagram of conventional technology

[Explanation of symbols]

10 In-office terminal equipment 11 Test disconnection circuit 20 Test circuit 21 DC current superimposition means 22 Polarity reversal means 23 Loss measurement means 30 In-home terminal equipment 31 Polarity reversal detection means 32 Switching means 33 Measurement signal sending means

Claims (1)

[Claims] [Claim 1] An in-office terminal device (10
) and the in-house terminating device (30) installed in the subscriber's premises.
In a two-wire digital subscriber line transmission system configured to be connected to a test circuit (20) by operating a test disconnection circuit (11) provided within the test circuit (20), DC current superimposition means (DC current superimposition means) for sending a DC current to the subscriber line (40) connected via the test disconnection circuit (11) when the test disconnection circuit (11) is in operation;
21), and polarity reversing means (21) for reversing the polarity of the DC current sent from the DC current superimposing means (21) to the subscriber line (40) when measuring the line loss of the subscriber line (40). 22) and a loss measuring means (23) for measuring the level of the measurement signal received through the subscriber line (40), and a loss measuring means (23) for measuring the level of the measurement signal received through the subscriber line (40), and polarity reversal detection means (31) that monitors the sent direct current and sends out a control signal for a certain period of time when detecting polarity reversal of the direct current;
switching means (32) for connecting the subscriber line (40) to the measurement signal sending means (33) while the control signal is being sent out from the polarity reversal detecting means (31); and the polarity reversal detecting means While the control signal is being sent from (31), the subscriber line (
measurement signal sending means (3) for sending a measurement signal to
3), the subscriber line loss measuring method is characterized in that loss of the subscriber line is measured by transmitting a measurement signal from the in-home termination device under control from the station.