JP2943240B2 - Subscriber line loop resistance determination circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a subscriber line loop resistance determining circuit for determining whether or not a loop resistance value of a subscriber line is equal to or more than a predetermined value. The present invention is to provide a subscriber line loop resistance determining circuit for determining whether or not a loop resistance value is equal to or more than a predetermined value without a loop resistance value. subscriber line loop resistance determination for determining whether or not the loop resistance R _L of the subscriber line is arbitrarily set in advance the loop resistance value R _L0 or more by measuring the loop current I _L supplied to the line in the circuit, a measuring resistor of the resistance value R which is inserted into one of the lines of the call line connecting the subscriber line and the power supply circuit, a constant ratio by measuring the dc voltage V _F which is output from the power supply circuit Power supply voltage index multiplied by β (β is an arbitrary value) a supply voltage measuring means for outputting a .beta.v _F, enter the voltage of said measuring resistor across measuring the loop current I _L flowing through the subscriber line, and wherein the measuring resistor the resistance with the loop current I _L The product of the value R was multiplied by a value α calculated such that αI _L0 · R = βV _F0 for the loop current I _L0 and the power supply voltage V _F0 when the loop resistance was set to the above-mentioned arbitrary loop resistance value R _L0 . and loop current measuring means for outputting a loop current index .alpha. I _L · R, the loop current index .alpha. I _L · R output from said power supply voltage index .beta.v _F output from the supply voltage measuring means and the loop current measuring means It is configured to include a loop resistance determining means for inputting and comparing, and outputting an output when one output is larger than the other output.

[Industrial applications]

The present invention relates to a subscriber line loop resistance determination circuit that determines whether a loop resistance value of a subscriber line is equal to or greater than a predetermined value.

In recent years, with the expansion of communication services, an amplifier circuit or a loss circuit is inserted into a communication circuit according to the loop resistance value of a subscriber line, or the impedance of a subscriber line in a passage circuit that performs 2-wire to 4-wire conversion. Measures for improving speech quality, such as changing the type of balanced network, have been increasingly used.

For example, in a subscriber terminal device, a method of inserting a loss circuit into a voice circuit and securing a constant communication quality when a loop resistance value of a subscriber line falls below a certain value is often adopted. . In such a case, a loop current flowing through the subscriber line is measured from a power supply circuit that supplies a DC voltage to the subscriber line, and when it is detected that the current value is equal to or greater than a preset value, an audio circuit of the subscriber line is detected. In general, a method of inserting a loss circuit into the circuit is used.

On the other hand, the power supply circuit for the subscriber line has been digitized, and a power supply circuit using a large-scale integrated circuit (hereinafter, referred to as LSI) has been generally used. The DC power supply uses a common power supply for communication equipment, which causes large voltage fluctuations.
Since the power supply circuit is also affected by deviations in the characteristics of the power supply circuit and temperature fluctuations, the output power supply voltage is inevitably accompanied by some fluctuations.

When the loop resistance value of the subscriber line is determined only by measuring the loop current flowing through the subscriber line, the fluctuation of the power supply voltage as described above is neglected. As a result, there is a possibility that the condition of the equipment delivery destination which stipulates that the loss circuit is inserted when the loop resistance value becomes equal to or less than a certain value may not be satisfied.

For this reason, a subscriber line loop resistance determination circuit that can accurately determine whether or not the loop resistance value is equal to or higher than a certain value without being affected by the fluctuation of the power supply voltage from the power supply circuit is required. I have.

[Conventional technology]

FIG. 5 is a configuration diagram of the prior art, and FIG. 6 is a loop resistance discrimination characteristic diagram of the prior art.

FIG. 5 shows, for example, a part of the configuration of a channel unit for a subscriber terminal equipment. A subscriber line 1 having a loop resistance value R _L in a closed state is connected to terminals A ₁ and B _1. Connected, and is supplied with a DC voltage from the power supply circuit 2. Further, the subscriber lines 1 are connected to the audio circuit 7 via the power supply circuit 2 from the terminal A _1, B _1, the resistance value of the subscriber line 1 into the voice circuit 7 is set in advance A loss switch 8 is provided for inserting a loss circuit into the talker when the resistance value is lower than the resistance value.

One of the communication lines from the power supply circuit 2 to the subscriber line 1,
For example, the terminal A ₁ side measuring resistor R of low value are connected in series, it is configured to loop current measurement circuit 11 calculates the loop current I _L the voltage across measures of the measuring resistor R ing. The loop current measurement circuit 11 also includes a loop current
From the measured value of I _L, the loop resistance value R _L is set to a preset resistance value R
_It discriminates whether it is less than _L0 , and if it is less than the set value, sends an output to the loss switch 8 of the audio circuit unit 7 and operates the loss switch 8 to make the communication circuit lose the loss circuit. Has a role to insert.

Now, the resistance R for measurement when the loop current _IL is flowing.
If both ends of the voltage V _R, is V _R = I _L · R, the measuring resistor R is the loop current I _L is obtained by measuring V _R because it is known. Therefore, when it is determined whether or not the loop resistance value _RL of the subscriber line 1 measured by the loop current measurement circuit 11 is equal to or less than, for example, an arbitrarily set loop resistance value R _L0, the loop resistance value R _L is determined in advance. calculating a loop current I _L0 which flows when the _L0 and stored, the measured loop current I
_It is determined whether or not _{L is} greater than the loop current I _L0 . If it is greater, it is determined that the loop resistance value _RL is equal to or less than a preset loop resistance value R _L0 , and an output is sent. Note that the loop resistance value of the subscriber line 1 is equal to the specific value R.
Previously stored voltage across V _L0 of the measuring resistor R when it is _L0, compared to the specific voltage V _L0 directly voltage V _R across the measuring resistor R in place of the loop current I _L The same result can be obtained.

In the above, the loop current I _L0 flowing when the loop resistance value is the specific value R _L0 is calculated on the assumption that the reference power supply voltage is output from the power supply circuit 2. While supply voltage V _P output from the power supply circuit 2 varies with loop resistance R _L, also the loop resistance R _L are the same, for example, a common power supply (shown in communication equipment which is supplied to the power supply circuit 2 Actually, it varies depending on the voltage fluctuation (omitted), the deviation of the characteristic of the internal circuit of the power supply circuit 2 and the temperature characteristic. Assuming that the supply voltage V _P output from the power supply circuit 2 is varied by such factors as described above, loop current I loop current measurement circuit 11 is measured under the supply voltage V _F which these variables were included even when the state of no change factors _L compared to certain of the loop current I ₀ which is calculated on the assumption the accuracy is lost.

The second Although drawing is an equivalent circuit diagram showing a simplified DC portion of the most basic power supply circuits, each of R _A and R _B of the feeding resistor 20
An example will be described in which 0Ω and R of the measurement resistor are 10Ω, and it is determined whether or not the loop resistance value _RL is equal to or less than a preset R _L0 = 500Ω.

Assuming that the reference value of the power supply voltage V _E of the power supply circuit is V _E = 48V, R
The loop current I _{L0 at L0} = 500Ω is I _L0 = 52.7 mA.

When the variation range of the power supply voltage V _E and 42~56V contrast, loop resistance value becomes I _L = 52.7mA in V _E = 42V and V _E = 56V R _L when the V _E = 42V R _L = 386Ω V _L = 652Ω when V _E = 56V.

FIG. 6 shows the loop resistance discriminating characteristic in the above example. As is clear from FIG. 6, the loop current _IL is measured by the loop current measuring circuit 11, and the measured loop current _IL is the reference voltage. I is the loop current when the loop resistance value R _L0 = 500Ω arbitrarily set at V _E = 48V
_L0 = _52.7mA loop resistance R _L depending on whether the larger is
When determining whether a 500Ω or less, so that the resulting large error by the value whether the power supply voltage V _E of the power supply circuit.

The method based on the comparison of the loop current is based on the above power supply voltage.
In addition to the fluctuation of V _E , for example, the power supply resistors R _A and R of the power supply circuit 2
Obviously, it is affected by the deviation of _B and the temperature characteristics.

As described above, the loop resistance determination method based on the measurement of the loop current in the related art is greatly affected only by the fluctuation of the power supply voltage of the power supply circuit, and further, the influence of the deviation of the power supply circuit and the temperature change is added. It is not possible to accurately determine whether the loop resistance value is equal to or greater than a certain value.

[Problems to be solved by the invention]

In the prior art, the loop current is measured to determine whether or not the loop resistance value is equal to or more than a certain value.However, since the loop current is affected by fluctuations in the power supply voltage output from the power supply circuit,
It has a disadvantage that it cannot be accurately determined.

An object of the present invention is to determine whether or not a loop resistance value is equal to or more than a certain value without being affected by a change in a power supply voltage of a power supply circuit.

[Means for solving the problem]

 FIG. 1 is a diagram illustrating the principle of the present invention.

In the drawing, 1 is a subscriber line, 2 is a power supply circuit for supplying a DC voltage to the subscriber line 1, and 3 is a resistor inserted into one of the communication lines connecting the power supply circuit 2 and the subscriber line 1. The resistance R for measuring the value R is a DC voltage V _F output from the power supply circuit 2.
Measured and fixed ratio beta (beta is an arbitrary value) supply voltage measuring means for outputting a power supply voltage index .beta.v _F multiplied by a, the subscriber line to input the voltage across the measuring resistor 3 5 the loop current I _L flowing in the measured and the product of the resistance value R of the loop current I _L and the measurement resistor 3, loop resistance value loop resistance value is set to the arbitrary (hereinafter, a particular loop resistance Note) Loop current I _L0 and supply voltage V _F0 when R _L0
The loop current measuring means for outputting a loop current index αI _L · R multiplied by a value α calculated such that αI _L0 · R = βV _F0 is obtained. 6 is the feed voltage index output from the feed voltage measuring means 4. βV _F and the loop current exponent αI _L · R output from the loop current measuring means 2 are input and compared, and when one output is greater than the other output, the loop resistance discriminating means sends out the output. is there.

(Operation)

FIG. 2 is an equivalent circuit diagram showing a simplified DC part of the most basic power supply circuit, and is used together with FIG. 1 to explain the operation of the present invention.

In FIG. 1, a subscriber line 1 having a loop resistance value R _L when closed is connected to terminals A and B,
It receives more DC voltage. The output of the power supply circuit 2 is connected to a supply voltage measuring means 4 measures the DC voltage V _F which is output from the power feeding circuit 2, the measured value V _F at a constant ratio beta of (beta arbitrary value) multiplied by calculates and outputs the power supply voltage index .beta.v _F.

Further, a measuring resistor 3 having a small resistance value R is connected in series to one of the communication lines from the power supply circuit 2 to the subscriber line 1, for example, the terminal A side, and the loop current measuring means 5 by measuring the voltage across R is adapted to calculate the loop current I _L flowing through the subscriber line 1. The loop current measuring means 5 also arbitrarily sets a specific loop resistance value R _L0 of the subscriber line 1 in advance, and determines a loop current flowing at the time of the loop resistance value R _L0 according to I _{L0 from} the power supply circuit. that keep the supply voltage and stores the value α calculated as the αI _L0 · R = βV _F0 is taken as V _F0, calculated loop current index .alpha. I _L · R when measured loop current I _L by the And output.

The feeding voltage loop current index .alpha. I _L · R output from the supply voltage index .beta.v _F and loop current measuring means 5 for measuring means 4 is from the output but the comparison is input to the loop resistance determining means 6 is carried out, following, This will be described with reference to FIG.

As described above, α is calculated such that αI _L0 · R = βV _F0 (1) when the specific loop resistance value is R _L0 , but the power supply voltage V _{F0 at} this time is calculated.
Is given by V _F0 = I _L0 (R _L0 + R) (2). _{Therefore, when} α is obtained from Expressions (1) and (2), α = β (R _L0 + R) / R (3)

When the loop current measuring means 5 which measures the loop current I _L loop resistance R _L flows through the subscriber line 1 is unknown, calculate the loop current index .alpha. I _L · R using the above α Output, the output loop current index αI _L · R
_{Is, αI L · R = βI L} · R (R L0 + R) / R = βI L (R L0 + R)
(4)

Further, supply voltage index .beta.v _F output from the supply voltage measuring means 4 at this time is _{βV F = βI L (R L} + R) (5).

Comparing (4) and (5), and regardless R _L0 = .alpha. I if only R _L is satisfied _{L · R = βV F (6} ) the value of I _L.

That is, the loop resistance measuring means 6 is connected to the loop current measuring means 5.
More loop current index .alpha. I _L · R, supply voltage index .beta.v _F from the supply voltage measuring means 4 is inputted, the loop resistance value measured when it is confirmed that match by comparing the two inputs
R _L means equal to a particular loop resistance value R _L0 .

At this time, the loop current I _L is I _L = V _E / (R _L0 + R + R _A + R _B ) (7). Therefore, the fact that the value of I _L is not relevant when the equation (6) is satisfied means that This indicates that the values of V _E , R _A , and R _B in equation (7) are not relevant. In other words, fluctuations in the power supply voltage V _E, R _A, R _B
It is proved that deviations of circuit elements in the power supply circuit and changes due to temperature characteristics do not affect the determination of the loop resistance value _RL .

Here, since V _F = V _E (R _L + R) / (R _L + R + R _A + R _B ) (8), V _F increases as the loop resistance value R _L increases, while the loop current I _L Is the loop resistance from equation (7)
It decreases as _RL increases. Therefore, the loop resistance value _RL when the formula (6) is not satisfied and the specific loop resistance value R
The magnitude relationship with _L0 is as follows.

<When _{βV F, R L> αI L} · R when _{R L0 αI L · R> βV} F, R L <R L0 Accordingly, the measured loop resistance R _L is smaller than the particular loop resistance R _L0 ( Or large), the output can be easily set in the loop resistance determining means 6,
In addition, this determination can be accurately performed without being affected by fluctuations in the power supply voltage, deviations in the power supply circuit, and temperature fluctuations.

〔Example〕

FIG. 3 is a configuration diagram of one embodiment of the present invention, and FIG. 4 is a loop resistance discrimination characteristic diagram of the embodiment of the present invention.

Throughout the drawings, the same symbols are used for the same objects, 2a is a power supply circuit LSI in the power supply circuit 2, 7 is a voice circuit unit to which the subscriber line 1 is connected via the power supply circuit 2, and 8 is the voice circuit. Part 7
Provided within, Los switch for insertion loss circuit speech path is lower than the resistance value resistor value is preset for the subscriber line 1, TR _A, TR _B is the transistors, R _A, R _B is supply resistor , V _E
Is a DC power supply for power supply.

In a third figure in LSI2a feeding circuit is built like an operational amplifier (not shown), the transistor TR _A, TR _B and the feeding resistors R _A, AC high impedance feed circuit 2 in combination with R _B, DC The circuit is configured to have low impedance.

In FIG. 3, the voice circuit unit 7 operates the loss switch 8 when the loop resistance value _RL of the subscriber line 1 is 500 Ω or less, and inserts a loss circuit (not shown) into the communication path. It is determined whether or not the loop resistance value _RL is 500Ω or less by the use resistor 3, the feed voltage measuring circuit 4, the loop current measuring circuit 5, and the loop resistance determining circuit 6, and when it is determined that the loop resistance value is 500Ω or less, Description will be made on the assumption that a signal is transmitted from the loop resistance determination circuit 6 to the loss switch 8.

Hereinafter, for simplicity of description, the equivalent circuit of FIG. 2 in which the power supply circuit in FIG. 3 is simplified is used, and the power supply resistance R _A =
R _B = 200Ω, resistance for measurement R = 10Ω, power supply voltage is V
An example in which _E = 48V and the fluctuation range is 42 to 56V will be described.

In the above example, at a specific loop resistance value R _L0 , the value of α that satisfies the above expression (1), that is, αI _L0 · R = βV _F0 , is obtained from the expression (3) as follows: α = β (R _L0 + R) / R = β (500 + 10) / 10 = 51β. Here, if β = 1, α = 51.

The alpha = 51, using beta = 1, the power supply voltage V _E = 42V, the fourth diagram calculating the loop resistance R changes and the loop current index _L .alpha. I _L · R and the power supply voltage indices .beta.v _F for 48VP and 56V Such a curve is obtained.

As apparent from FIG. 4, even if the power supply voltage V _E varies, the supply voltage indices .beta.v _F and loop current index .alpha. I _L · R is always cross at the loop resistance R _L = 500Ω. Therefore, in the loop resistance determination circuit 6, the loop current index αI _L · R
Be set such who sends out an output signal when a larger than supply voltage index .beta.v _F, Los switch 8 audio circuit portion 7 operates when the loop resistance R _L of the following 500 [Omega,
A loss circuit will be inserted.

The power supply circuit 2 in FIG. 3 has a more complicated configuration than that in FIG. 2 as shown, and there is a possibility that the circuit constant may change due to the deviation of circuit elements or temperature fluctuation. Even if there is a deviation not only in _E but also in the power supply circuit element or the like, there is no effect on the determination of the loop resistance value _RL .

In the above, the specific loop resistance value of R ₁₀
= Was used 500 [Omega, the particular loop resistance value can be arbitrarily set, the loop resistance R _L was measured by using to calculate the α corresponding to the particular loop resistance R _L0 set It is clear that it is possible to accurately determine whether is greater (or smaller) than the specific loop resistance value R _L0 .

Note that FIG. 3 is merely an example of the present invention, and the configuration of the power supply circuit and the like can be other than that of FIG. 3. It is clear that the invention is applicable and the invention does not exclude these variants.

[Effects of the Invention] As described above, according to the present invention, the loop resistance is set to a predetermined value without being affected by the fluctuation of the power supply voltage of the power supply circuit with respect to the subscriber line, the deviation of the power supply circuit, or the temperature fluctuation. It is possible to accurately determine whether or not the value is equal to or greater than the value. This has a remarkable effect on improving the characteristics of the subscriber line loop resistance determination circuit, and the quality of voice quality improvement means using the subscriber line loop resistance determination. It is a great contributor to improvement.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is an equivalent circuit diagram of a power supply circuit, FIG. 3 is a configuration diagram of an embodiment of the present invention, FIG. FIG. 5 is a configuration diagram of the prior art, and FIG. 6 is a loop resistance discrimination characteristic diagram of the prior art. In the figure, 1 ... subscriber line 2 ... power supply circuit 3 ... measuring resistor 4 ... power supply voltage measuring means 5 ... loop current measuring means 6 ... loop resistance discriminating means.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01R 27 / 02,27 / 16 H04M 3/30

Claims (1)

(57) [Claims] [Claim 1, wherein the subscriber lines by measuring the loop current I _L supplied to the subscriber line of the closed state from the power supply circuit (2) supplies a DC voltage to the subscriber line (1) (1) In the subscriber line loop resistance determining circuit for determining whether or not the loop resistance value _RL of (1) is equal to or more than an arbitrarily set loop resistance value _RL0 , the power supply circuit (2) and the subscriber line ( A resistance (3) for measuring the resistance R inserted into one of the communication lines connecting 1)
When the power supply circuit (2) DC voltage V _F which is output from the measured (the β arbitrary value) fixed ratio β to output the power supply voltage index .beta.v _F multiplied by the supply voltage measuring means (4) the enter the voltage across the measuring resistor (3) to measure the loop current I _L flowing through the subscriber line (1), and the loop current I _L and the resistance value of the measurement resistor (3) For the loop current I _L0 and the supply voltage V _F0 when the loop resistance is set to the above-mentioned arbitrary loop resistance value R _L0 , αI _L0 · R =
a loop current measuring means (5) for outputting a loop current index αI _L · R multiplied by a value α calculated to be βV _F0; and the power supply voltage index βV _F output from the power supply voltage measuring means (4). And the loop current exponent αI _L · R output from the loop current measuring means (2) is inputted and compared, and when one output is larger than the other output, the loop resistance determining means ( 6) A subscriber line loop resistance discriminating circuit, comprising: