JP2880006B2 - ISDN subscriber line measuring method and measuring apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to analog subscriber lines and I
Apparatus and method for testing a subscriber line with an SDN subscriber.

[0002]

2. Description of the Related Art Conventionally, ISDN subscriber line tests are performed using a dedicated medium test panel (LTE), and a measurement circuit is required separately from the analog subscriber line test. This is because the existing analog subscriber line measurement uses the single-line grounding method to measure the capacitance and insulation resistance between the A and B lines by grounding either the A or B line to the ground, In the subscriber line test for ISDN subscribers, both line capacitance and line insulation resistance are A and B.
This is because the measurement is performed by the floating method in which the wire is insulated from the ground.

[0003] The following describes the analog subscriber line test and ISDN.
A conventional measurement method with the subscriber line test will be described.

First, the line measurement of an analog subscriber line has been conventionally performed by a single-line grounding method. This is because the line measurement was performed under the same conditions as the communication because the analog voice was communicated by the grounding method. In this case, if any one of the insulation between the ground and the line becomes defective, high-quality service cannot be performed.

On the other hand, in the case of ISDN subscribers, data communication is performed by using a line AC voltage insulated from the ground.
Therefore, it is only necessary to ensure line insulation by floating, and insulation failure of only one line does not affect communication. Therefore, the ISDN subscriber line is measured by a floating method. As a document relating to ISDN subscriber line test, for example, “Advanced function of ISDN metallic subscriber line transmission device” (NTTR & D Vol.39 N0.8)
1990).

Conventionally, a line test is performed for each of the analog subscriber line and the ISDN subscriber line by using a separate measurement circuit because of the difference between the above-described measurement methods.

[0007]

In a small station, an analog subscriber line and an ISDN subscriber line are mixed and accommodated by using an analog / ISDN mixed remote multiplex transmission apparatus.
Aiming at the spread of DN.

However, in the above-mentioned prior art, a separate measurement circuit is required for analog subscriber line measurement and ISDN subscriber line measurement, respectively. Therefore, analog subscriber lines and ISDN subscriber lines are mixed and accommodated. There is a problem in that small-scale stations are inefficient and uneconomical.

It is an object of the present invention to provide an analog subscriber line and I
An object of the present invention is to realize a subscriber line test apparatus capable of measuring an SDN subscriber line using the same measurement circuit.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a measuring apparatus for measuring a subscriber line, comprising: measuring a ground-to-ground capacitance and a ground resistance of the subscriber line; A line measurement circuit that measures the line capacitance and line resistance when one line is grounded, and the line capacitance and line insulation when measured with the ground insulated from the measurement results of the line measurement circuit. This is achieved by having a conversion processing unit for calculating a resistance value.

Further, the apparatus may include an input unit for receiving an instruction of the start of measurement and a test item and instructing the conversion processing unit, and an output unit for outputting a measurement result.

[0012] When the analog subscriber line is tested, the conversion processing unit measures the ground-to-ground capacitance and ground-to-ground resistance of the subscriber line, and measures the line-to-line when one of the subscriber lines is grounded. Outputs the measurement results of the measurement of capacitance and line resistance,
When testing N subscriber lines, from the above measurement results,
It is possible to output a calculation result obtained by calculating a line capacitance and a line insulation resistance value when measured while insulated from the ground.

The input unit can receive an instruction to select which of the analog subscriber line test and the ISDN subscriber line test to perform, and instruct the conversion processing unit.

A line discharging circuit for discharging the charge of the subscriber line before the measurement, and a switching connection circuit for connecting the subscriber line to the line discharging circuit before the measurement and switching the connection to the line measuring circuit after the discharging. Can have.

The conversion processing unit calculates the line resistance Rf and the line capacitance Cf when measured with insulation from the ground.
The ground resistances Ra and Rb of the subscriber line and the ground capacitance C
a and Cb, the measurement result of the line resistance Rab when one side of the subscriber line is grounded, and the line capacitance Cab,

[0016]

(Equation 5)

[0017]

(Equation 6)

It can be obtained from the above equation.

[0019]

When testing an analog subscriber line in a measuring apparatus for measuring a subscriber line, when measuring the ground capacitance and the ground resistance of the subscriber line, and grounding one line of the subscriber line to ground. Measurement of line capacitance and line resistance when
When the measurement result is output and the ISDN subscriber line test is performed, the line capacitance and line insulation resistance value measured when the measurement is performed insulated from the ground is output from the above measurement result and the calculation result is output. Then, analog and ISDN are measured by the same method.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a functional block diagram of a subscriber line measuring instrument showing an embodiment of a subscriber line measuring method according to the present invention. In FIG. 1, a higher-level device 27 is an input / output device, gives an input instruction to a subscriber line measuring instrument, and outputs a result from an output unit. The host device 27 includes an instruction unit such as a keyboard for giving instructions, a display unit such as a display or a printer, and a processing unit for giving instructions to the digital signal processor 25. The host device 27 is connected to the serial interface circuit 26 via a transmission line. The serial interface circuit 26 includes, for example, a host device 27
Can be converted to serial data when the data from is parallel data. The measurement instruction from the host device 27 is sent to the digital signal processor 25 via the serial interface circuit 26. The digital signal processor 25 is a conversion processing unit, analyzes a measurement instruction, controls the switching connection circuit 22, the line discharge circuit 23, and the line measurement circuit 24 according to the instruction, and connects the subscriber line 21 by a single-wire grounding method. Measure. The digital signal processor 25 has software therein and instructs each circuit according to a program. The test method includes an automatic measurement method for automatically performing all test items and a method for giving an instruction from the higher-level device 27 for each item. The switching connection circuit 22 is a switching circuit for switching the connection to the subscriber line 21 to a line discharging circuit 23 and a line measuring circuit 24, and is a digital signal processor 2
It switches according to the instruction from 5. Line discharge circuit 23
Is a circuit for discharging the electric charge stored in the subscriber line 21 or the terminal before the measurement. The line discharge circuit 23 is grounded via a high resistance and discharges for a fixed time. The line measuring circuit 24 is a circuit of a subscriber line measuring device shown in FIGS. 2 and 3 described later. The measurement circuit shown in this embodiment performs measurement in a telephone office.

Next, a description will be given of a case where a test is performed in the subscriber line measuring device shown in FIG. First, when there is a test start instruction from the host device 27, the digital signal processor 25 receives the instruction via the serial interface circuit 26. The digital signal processor 25 determines whether the test is analog subscriber line measurement or ISDN.
Measurement of the subscriber line or an instruction from the host device 27 is accepted. The digital signal processor 25 instructs the switching connection circuit 22 to connect the line discharge circuit 23 to the subscriber line 21. When the discharge is completed after a lapse of a predetermined time, the digital signal processor 25 sends the subscriber line 21 to the switching connection circuit 22 through the line discharge circuit 23.
From the line measurement circuit 24. After the connection, measurement is performed by the line measurement circuit 24. Test items include the items shown in Table 1, and each item is tested. The test can be performed automatically for all items, or each item can be specified by the higher-level device 27.

[0023]

[Table 1]

The external voltage measurement of item 1 and the measurements of items 4 to 7 are performed in the same manner as in the prior art, and the capacitance measurement of item 2 and the resistance measurement of item 3 are performed by the following method. First, the digital signal processor 25 operates as shown in FIG.
The resistance is measured by the single-wire grounding method shown in FIG. Next, switching to the measurement circuit as shown in FIG. 2 is performed to obtain the resistance between the ground and the capacitance between the grounds. In the case of measurement of an analog subscriber line, the measurement result is output to the host device 27 as it is. In the case of measurement of the ISDN subscriber line, a calculated value corresponding to the floating measurement result is calculated by a numerical calculation method described later and returned to the host device 27.

Next, an embodiment of a method for calculating the difference between the single-wire grounding method and the floating method by numerical calculation will be described with reference to FIGS. FIG. 2 is a diagram illustrating the principle of measurement when measuring the resistance between the ground and the capacitance between the grounds. The subscriber line indicates a distributed constant circuit of C and R, and can be considered by replacing it with an equivalent circuit as shown in FIG. In FIG. 2, there are an A line 1 and a B line 2 connected to the terminal, and the ground resistance Ra
7, Rb8, ground capacitances Ca10 and Cb11, line resistance Rab9 and line capacitance Cab12. And A line 1
And the B line 2 are connected to a subscriber line measuring device. By applying a voltage E3 of the same potential to line A1 and line B2 as shown in FIG. 2 and measuring the voltmeter V4, ammeter AA5, and ammeter AB6 as shown in FIG. 2, the resistances Ra7 and Rb8 between the ground and ground are measured. , And the earth-to-ground capacities Ca10 and Cb11. A line 1,
Since the B line 2 has the same potential, the components of Rab9 and Cab12 are not included in the measurement result.

FIG. 3 shows a line resistance Rab by a single-wire grounding method.
9 is a measurement principle diagram for measuring the line capacitance Cab12. As shown in FIG. 3, when the B line 2 is grounded inside the measuring instrument, the voltage E3 is applied to the A line 1, and the voltmeter V4 and the ammeter AA5 are measured, the values obtained by resistance Rg and capacitance Cg are as follows. , Rg and Cg are given by the following equations.

[0027]

(Equation 1)

[0028]

(Equation 2)

By transforming the equations (1) and (2),

[0030]

(Equation 3)

[0031]

(Equation 4)

## EQU1 ## By substituting the ground resistance Ra7 and ground capacitance Ca10 measured by the circuit shown in FIG. 2 and Rg and Cg measured by the circuit shown in FIG. 3, the line resistance Rab9 and the line capacitance Cab12 are obtained. Can be calculated.
Switching between the circuit shown in FIG. 2 and the circuit shown in FIG.
For example, a switch may be provided on the B line 2 on the subscriber line side of the ammeter AB6 to switch between the grounding side and the ammeter AB6 side. The switching instruction is issued from the digital signal processor 25. The A line 1 may be grounded.

As described above, using Ra7, Rb8, Ca10 and Cb11 measured by the circuit shown in FIG. 2 and Rab9 and Cab12 calculated by the circuit shown in FIG. Line resistance R
f, the line capacitance Cf can be calculated.

[0034]

(Equation 5)

[0035]

(Equation 6)

In FIG. 4, Rf and Cf are obtained by connecting a voltage E3 insulated from the ground between the A line 1 and the B line 2 and measuring a voltmeter V4 and an ammeter AA5.
It is equal to the measured value of line resistance and line capacitance by the floating method.

That is, the measurement by the single-wire grounding method shown in FIGS. 2 and 3 and the calculations from the equations (1) to (6) are realized by software provided inside the digital signal processor 25 in the functional block diagram of FIG. Thus, the difference between the single-wire grounding method and the floating method can be calculated by numerical calculation.

As described above, the analog subscriber line and the ISDN subscriber line can be measured by one measuring device by using the above-described circuit.

[0039]

According to the present invention, it is possible to obtain a measurement result suitable for the purpose of ISDN subscriber line measurement and to perform analog line measurement, thereby realizing an economical ISDN line test apparatus. Become.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a measuring device of the present invention.

FIG. 2 is a diagram showing the principle of measurement when measuring the resistance between grounds and the capacitance between grounds.

FIG. 3 is a measurement principle diagram for measuring line resistance and line capacitance by a single-wire grounding method.

FIG. 4 is a measurement principle diagram for measuring line resistance and line capacitance by a floating method.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 subscriber line 2 switching connection circuit 3 line discharge circuit 4 line measurement circuit 5 digital signal processor 6 serial interface circuit 7 host device

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-163369 (JP, A) JP-A-64-2457 (JP, A) JP-A-57-135563 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) H04M 3/26-3/30

Claims (9)

(57) [Claims] 1. A measuring apparatus for measuring a subscriber line, comprising: measuring a ground-to-ground capacitance and a ground-to-ground resistance of the subscriber line; and measuring a line-to-line capacitance and a line-to-line resistance when one of the subscriber lines is grounded. And a conversion processing unit that calculates a line capacitance and a line insulation resistance value when measured insulated from the ground from the measurement result of the line measurement circuit. ISDN subscriber line measuring device. 2. The ISDN subscriber line measuring apparatus according to claim 1, further comprising an input unit for receiving an instruction of a start of measurement and a test item and instructing a conversion processing unit. 3. The ISDN according to claim 1, further comprising an output unit for outputting a measurement result.
Subscriber line measurement device. 4. A conversion processing unit according to claim 1, wherein the conversion processing section measures a capacitance and a ground resistance of the subscriber line when testing an analog subscriber line. Output the measurement results of the line capacitance and line resistance when one of the wires is grounded. When testing the ISDN subscriber line, the measurement was performed with the ground insulated from the above measurement results. An ISDN subscriber line measuring apparatus, which outputs a calculation result obtained by calculating a line capacitance and a line insulation resistance at the time. 5. An input unit according to claim 4, wherein the input unit accepts an instruction to select which of an analog subscriber line test and an ISDN subscriber line test to perform, and instructs the conversion processing unit. An ISDN subscriber line measuring apparatus. 6. The method of claim 1, 2, 3, 4, or 5,
A line discharge circuit for discharging the charge of the subscriber line before the measurement,
An ISDN subscriber line measuring apparatus, further comprising: a switching connection circuit for connecting a subscriber line to a line discharging circuit before measurement and switching the connection to the line measuring circuit after discharging. 7. The conversion processing unit according to claim 1, wherein the conversion processing unit determines a line resistance Rf and a line capacitance Cf when measured while insulated from the ground. Line-to-ground resistances Ra and Rb and line-to-ground capacitances Ca and Cb
And the line resistance Rab when one side of the subscriber line is grounded,
The measurement result of the line capacitance Cab, and (Equation 6) An ISDN subscriber line measuring apparatus characterized by being obtained from the above equation. 8. A measuring apparatus for measuring a subscriber line, wherein when testing an analog subscriber line, a measurement of a ground-to-ground capacitance and a ground-to-ground resistance of the subscriber line and a single line of the subscriber line are performed. The measurement of the line capacitance and line resistance when the ground is grounded, and the output of the measurement results. A subscriber line measuring method for calculating a line capacitance and a line insulation resistance value and outputting a calculation result. 9. In the test of an ISDN subscriber line according to claim 8, the line resistance Rf and the line capacitance Cf measured insulated from the ground are determined by determining the distance between the ground of the subscriber line. Resistances Ra and Rb, earth-to-ground capacitances Ca and Cb,
A measurement result of the line resistance Rab and the line capacitance Cab when one side of the subscriber line is grounded, and (Equation 6) A subscriber line measurement method characterized in that it is obtained and output from the above equation.