JPH0424570A - Discrimination circuit of loop resistance of subscriber's line - Google Patents

Abstract

PURPOSE:To make a discrimination as to whether a loop resistance value is a prescribed value or above or not, without being affected by a fluctuation in a feed voltage of a feeding circuit, by comparing a feed voltage index outputted from a feed voltage measuring means with a loop current index outputted from a loop current measuring means. CONSTITUTION:A specified loop resistance value RLO of a subscriber's line being set arbitrarily beforehand, a value alpha calculated so that an equation alphaILO.R = betaVFO be established when a loop current flowing at said loop resistance value RLO is denoted by ILO and a feed voltage by VFO, is stored, and a loop current index alphaIL.R is calculated and outputted when a loop current IL is measured. A feed voltage index betaVF outputted from a feed voltage measuring means 4 and the loop current index alphaIL.R outputted from a loop current measuring means 5 are inputted to a loop resistance discriminating means 6 and compared with each other. Accordingly, delivery of an output in the case when a measured loop resistance value RL is smaller (or larger) than the specified loop resistance value RLO can be set easily in the loop resistance discriminating means 6, and this discrimination is performed accurately without being affected by a fluctuation in a source voltage or a deviation or a temperature change inside a feeding circuit.

Description

[Detailed Description of the Invention] [Summary] Regarding a subscriber line loop resistance determination circuit that determines whether the loop resistance value of a subscriber line is equal to or higher than a certain value, The purpose of the present invention is to provide a subscriber line loop resistance determination circuit that determines whether or not the loop resistance value is equal to or higher than a certain value without causing any damage to the subscriber line. A subscriber line loop resistance that determines whether the loop resistance value RL of the subscriber line is greater than or equal to a preset arbitrarily set loop resistance value RL,o by measuring the loop current I+ supplied to the line. In the discrimination circuit, a resistor for measuring a resistance value R inserted into one line of a communication line connecting the power supply circuit and the subscriber line and a DC voltage V output from the power supply circuit are measured and a constant voltage is determined. A power supply voltage measuring means that outputs a power supply voltage index βVF multiplied by a ratio β (β is an arbitrary value), and a loop current IL flowing through the subscriber line by inputting the voltage across the measuring resistor, and the product of the loop current It and the resistance value R of the measuring resistor, the loop current ILO and the power supply voltage N' when the loop resistance is set to the arbitrary loop resistance value RLO. About αI
a loop current measuring means that outputs a loop current index α■,・R multiplied by a value α calculated so that LO'R=βVPO; The loop resistance determining means inputs and compares the loop current index αIL -R outputted from the current measuring means, and sends out an output when one output is larger than the other output.

[Industrial application field]

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

In recent years, with the expansion of communication services, amplification circuits and loss circuits have been inserted into communication circuits according to the loop resistance value of the subscriber line, and in communication circuits that perform 2-wire to 4-wire conversion, according to the impedance of the subscriber line. Measures to improve call quality, such as changing the type of balanced circuit network, are increasingly being used.

For example, in subscriber terminal equipment, a method is often adopted in which a loss circuit is inserted into the audio circuit to ensure a certain level of call quality when the loop resistance value of the subscriber line falls below a certain value. . In such a case, measure the loop current flowing to the subscriber line from the power supply circuit that supplies DC voltage to the subscriber line,
A commonly used method is to insert a loss circuit into the audio circuit of the subscriber line when it is detected that the current value is greater than a preset value.

On the other hand, as power supply circuits for subscriber lines are increasingly computerized, it has become common to use power supply circuits based on large-scale integrated circuits (hereinafter referred to as LSI). Because the common power supply for communication equipment is used as the DC voltage power supply, voltage fluctuations are large (in addition, the LS
Since it is also influenced by deviations in the characteristics of the I power supply circuit and temperature fluctuations, it is inevitable that the output power supply voltage will fluctuate to some extent.

If the loop resistance value of the subscriber line is determined only by measuring the loop current flowing through the subscriber line, the above-mentioned fluctuations in the power supply voltage will be ignored, which will cause errors in the measurement results and affect the call quality. In particular, when the loop resistance value falls below a certain value, there is a possibility that the conditions of the device delivery destination, which stipulate that a loss circuit be inserted, may not be satisfied.

Therefore, there is a need for a subscriber line loop resistance determination circuit that can accurately determine whether the loop resistance value is above a certain value without being affected by fluctuations in the power supply voltage from the power supply circuit. There is.

[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 a part of the configuration of a channel unit for a subscriber system terminal equipment, for example, and the subscriber line l whose loop resistance value in the closed circuit state is RL is connected to the terminal AB1, and the power supply circuit DC voltage is supplied from 2. Further, the subscriber line 1 is connected to the audio circuit section 7 from the terminals At and B+ via the power supply circuit 2.
A loss switch 8 is provided for inserting a loss circuit into the communication path when the resistance value of the intensifier line l is lower than a preset resistance value.

A measuring resistor R of a small value is connected in series to one side of the communication line from the power supply circuit 2 to the subscriber line L, for example, the terminal A1 side, and the loop current measuring circuit 11 measures the voltage across the measuring resistor R. It is configured to measure the loop current and calculate the loop current. The loop current measurement circuit 11 also identifies whether the loop resistance value RL is less than or equal to a preset resistance value RL,o from the measured value of the loop current (2), and if it is less than or equal to the preset value, the audio circuit It has the role of sending an output to the loss switch 8 of the section 7, operating the loss switch 8, and inserting a loss circuit into the communication circuit.

Now, when the loop current ■ is flowing, the measuring resistance R
If the voltage across both ends is VR, then VR=I,·R, and since the measuring resistance R is known, the loop current I+ can be obtained by measuring V. Therefore, when identifying whether or not the loop resistance value R5 of the subscriber line l measured by the loop current measurement circuit 11 is, for example, below an arbitrarily set loop resistance value RLO, in advance, if the loop resistance value RLO is The loop current ILO flowing in is calculated and stored, and the measured loop current IL is the loop current ILO. If it is larger, it is determined that the loop resistance value RL is less than or equal to a preset loop resistance value RLO, and an output is sent. Note that the voltage VLO across the measuring resistor R when the loop resistance value of the subscriber line 1 is the specific value RL11 is stored in advance,
Loop current 1. Instead of the voltage V across the measuring resistor R
The same result can be obtained by comparing R directly with the specified voltage VLo.

In the above description, the loop current ILO that flows when the loop resistance value is a specific value RLO is calculated on the premise that the reference power supply voltage is output from the power supply circuit 2.

The power supply voltage VF output from the power supply circuit 2 varies depending on the loop resistance value RL, but even if the loop resistance value RL is the same, for example, if the power supply voltage VF output from the power supply circuit 2 is common to the communication equipment (not shown), The reality is that it changes depending on voltage fluctuations, deviations in the characteristics of the internal circuit of the power supply circuit 2, and temperature characteristics. If the power supply voltage VF output from the power supply circuit 2 fluctuates due to the factors mentioned above, the loop current measuring circuit 1 will be
1 is a specific loop current I calculated on the assumption that there are no fluctuation factors in the measured loop current IL. Accuracy is lost when compared to

Figure 2 is a simplified equivalent circuit diagram of the DC part of the most basic power supply circuit.The power supply resistances RA and R3 are each 200Ω, the measurement resistor R is IOΩ, and the loop resistance value R5 is An example of determining whether or not R4° is equal to or less than a preset value of 500Ω will be described.

If the reference value of the power supply voltage V6 of the power supply circuit is VE = 48V, the loop current ILO at RLO = 500Ω is
ILO=52. It becomes 7 mA.

On the other hand, if the fluctuation range of the power supply voltage V6 is 42 to 56V, then at Vl:=42V and VE=56V, 1
The loop resistance value RL for L=52.7mA is: When V=42V, R,-'386ΩVE=56
When V, RL=652Ω.

FIG. 6 shows the loop resistance discrimination characteristics in the above example, and as is clear from the figure, the loop current measurement circuit 11 has a loop current of 1. The measured loop current IL is the loop current when the reference voltage V=48V and the arbitrarily set loop resistance value RLO=500Ω.

The loop resistance value R depends on whether it is greater than 52.7mA.
Determining whether L is 500Ω or less may result in a large error depending on the value of the power supply voltage V6 of the power supply circuit.

Note that the method based on comparison of loop currents is based on the power supply voltage V
, (for example, the power supply resistance RA of the power supply circuit 2)
, RB deviation and temperature characteristics are obviously affected.

As described above, the conventional method of determining loop resistance by measuring loop current is greatly affected by fluctuations in the power supply voltage of the power supply circuit, and is also affected by deviations and temperature changes in the power supply circuit, so It is not possible to accurately determine whether the loop resistance value is greater than or equal to a certain value.

[Problem to be solved by the invention]

In conventional technology, loop current is measured to determine whether the loop resistance value is above a certain value, but since it is affected by fluctuations in the power supply voltage output from the power supply circuit, accurate determination is required. It has the disadvantage that it cannot be used.

An object of the present invention is to determine whether a loop resistance value is equal to or greater than a certain value without being affected by fluctuations in the power supply voltage of a power supply circuit.

[Means to solve the problem]

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

In the figure, ■ is a subscriber line, 2 is a feeder circuit that supplies DC voltage to the subscriber line l, and 3 is the feeder circuit 2 and the subscriber line l.
4 is the DC voltage V output from the power supply circuit 2,
A power supply voltage measuring means 5 outputs a power supply voltage index βVF obtained by measuring and multiplying by a certain ratio β (β is an arbitrary value);
The loop current It flowing through is measured, and the loop resistance value is the product of the loop current IL and the resistance value R of the measurement resistor 3, and the loop resistance value is the arbitrarily set loop resistance value (hereinafter referred to as the specific loop resistance value). ) Loop current ILO when RLO
and supply voltage V,. The loop current index multiplied by the value α calculated such that αILO・R=βVFO,
・Loop current measuring means for outputting R; 6 inputs the power supply voltage index βVF outputted from the power supply voltage measuring means 4 and the loop current index α■ outputted from the loop current measuring means 2; ・R; This is a loop resistance determining means that compares the two outputs and sends an output when one output is larger than the other.

[For production]

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

In FIG. 1, a subscriber line 1 whose loop resistance value when closed is RL is connected to terminals A and B, and is supplied with DC voltage from a power supply circuit 2. A power supply voltage measuring means 4 is connected to the output part of the power supply circuit 2, and measures the DC voltage V outputted from the power supply circuit 2, and sets a certain ratio β (β is an arbitrary value) to the measured value V. Multiply the power supply voltage index βVF
Calculate and output.

Further, a measuring resistor 3 having a small resistance value R is connected in series to one side of the communication line from the power feeding circuit 2 to the subscriber line I, for example, the terminal A side, and the loop current measuring means 5 is connected to the measuring resistor 3. By measuring the voltage across R, the loop current I flowing through the subscriber line I is calculated. The loop current measuring means 5 also arbitrarily sets a specific loop resistance value R5° of the subscriber line l in advance, and sets the loop resistance value RL,
The loop current that flows when o is ILo, and the supply voltage from the supply circuit is V. αI when closed.・
Store the value α calculated so that it becomes R-βVFO,
When the loop current I is measured as described above, the loop current index αI,·R is calculated and output.

The power supply voltage index β output from the power supply voltage measuring means 4
VF and the loop current index αI, .R outputted from the loop current measuring means 5 are input to the loop resistance determining means 6 for comparison, which will be explained below with reference to FIG.

As mentioned above, when the loop resistance value RLO is (2I
I calculated α such that LO”R=βVFO(t), but the power supply voltage ■,
. is, VFO= I LO(PLO+R) (2+
Therefore, when α is determined from equations (1) and (2), it becomes α−β(RLO+R)/R(3).

When the loop current measuring means 5 measures the loop current IL flowing through the subscriber line l whose loop resistance value RL is unknown, the loop current index αIL'R is determined using the above α.
is calculated and output, but the output loop current index α■
,・R is αIL・R=βIL・R(RLO+R)
/R=βIL (RLO+R) (41.

Further, the power supply voltage index βVF outputted from the power supply voltage measuring means 4 at this time is βVF=βIL (RL +R) (5).

Comparing equations (4) and (5), we find that regardless of the value of IL, if only RL, o= RL holds, then αIL-R=β
V p (becomes 61).

That is, the loop current index αI is input from the loop current measuring means 5 to the loop resistance determining means 6, and the power supply voltage index βVF is input from the R1 power supply voltage measuring means 4, and it is confirmed that they match by comparing the power of both persons. This means that the measured loop resistance value RL is equal to the specific loop resistance value RL,o.

At this time, the loop current ■ is I L = VE / (RLO + R + RA + RB
), so when equation (6) holds true, 1. The fact that the values of VE, RA, and VE in equation (7) are unrelated means that
This shows that the RaO value is not relevant. That is, fluctuations in the power supply voltage VE, deviations in circuit elements in the power supply circuit such as RA and RB, and changes due to temperature characteristics affect the loop resistance value RL.
It is proven that this does not affect the discrimination of

Here, since V, -VE (RL + R) / (RL + R + Ra + Ra) (8), ■ increases as the loop resistance value RL increases, while the loop current IL becomes (7 ), it decreases as the loop resistance value R5 increases.

Therefore, the loop resistance value R5 when equation (6) does not hold
The magnitude relationship between and specific loop resistance values RL and O is as follows.

When αI,・R×βVF, RL, > RLOα■
, ·R>βVF, RL < RLO Therefore, the loop resistance determining means 6 can easily send an output when the measured loop resistance value RL is smaller (or larger) than the specific loop resistance value RLO. This determination can be made accurately without being affected by power supply voltage fluctuations, internal deviations in the power supply circuit, or temperature fluctuations.

〔Example〕

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

The same symbols are used for the same objects throughout the drawings, 2a is the power feeding circuit LSI in the power feeding circuit 2, 7 is the audio circuit section to which the subscriber line l is connected via the power feeding circuit 2, and 8 is the audio circuit. A loss circuit is provided in the section 7 and inserts a loss circuit into the communication path when the resistance value of the subscriber line I is lower than a preset resistance value.
Switches, TRA, TR, are transistors, RA, RB
is the power supply resistance, and ■ is the DC power supply for power supply.

In FIG. 3, an operational amplifier (not shown) is built in the power supply circuit LSIZa, and transistors TRA and T
In combination with RB and the feed resistors RA and R, the feed circuit 2 is configured to have high impedance in AC and low impedance in DC.

In FIG. 3, the audio circuit unit 7 switches the loss switch 8 when the loop resistance value RL of the subscriber line l is 500Ω or less.
is operated and a loss circuit (not shown) is inserted into the communication path, and the measuring resistor 3, the supply voltage measuring circuit 4, the loop current measuring circuit 5, and the loop resistance determining circuit 6 determine that the loop resistance value RL is 500Ω or less. Determine whether or not there is, 5
The explanation will be made assuming that the loop resistance discrimination circuit 6 sends a signal to the loss switch 8 when it is determined that the resistance is 00Ω or less.

Hereinafter, in order to simplify the explanation, the equivalent circuit in Fig. 2, which is a simplified version of the feed circuit in Fig. 3, will be used, and the feed resistance RA
= RB = 200 Ω, measurement resistance R = 10 Ω, and the reference value of the power supply voltage is VE = 48 V.

An example in which the fluctuation range is 42 to 56 V will be explained.

In the above example, at a specific loop resistance value RLO, the above equation (1) is satisfied, that is, αILO·R=βVF.

From equation (3), the value of α that satisfies α−β(P L O + R) / R =β(500+IO)/10 =51β becomes. Here, if β; 1, β；51 becomes.

Using this α-51, β=1, the power supply voltage VE = 4
Loop resistance value R for 2V, 48V and 56V,
Changes in loop current index αI, ·R and supply voltage index β
By calculating (2), a curve as shown in FIG. 4 is obtained.

As is clear from FIG. 4, even if the power supply voltage V varies, the loop current index αIL -R and the supply voltage index β■,
always intersect at the loop resistance value RL=500Ω. Therefore, if the loop resistance determination circuit 6 is set to send an output signal when the loop current index αIL''R is larger than the power supply voltage index βVF, the loop resistance value RL is 500Ω or less. Loss of audio circuit section 7
Switch 8 is operated and a loss circuit is inserted.

The power supply circuit 2 in FIG. 3 has a more complicated configuration than that shown in FIG. Even if there is a deviation not only in the voltage V but also in the feeder circuit elements, it does not affect the determination of the loop resistance value R5.

Furthermore, in the above, R5゜=500Ω was used as the specific loop resistance value, but the specific loop resistance value can be set arbitrarily, and the set specific loop resistance value RL
It is clear that by calculating and using α according to O, it is possible to accurately determine whether the measured loop resistance value RL is larger (or smaller) than the specific loop resistance value RL(l).

It should be noted that FIG. 3 is just one embodiment of the present invention.
Although the configuration of the power supply circuit etc. can be changed to a configuration other than that shown in FIG. 3, it is clear that the present invention is applicable even if the configuration of the power supply circuit etc. is changed, and the present invention does not apply to these modifications. It does not exclude.

〔Effect of the invention〕

As explained above, according to the present invention, the loop resistance value is equal to or greater than the preset resistance value without being affected by fluctuations in the power supply voltage of the power supply circuit to the subscriber line, deviations in the power supply circuit, or temperature fluctuations. It becomes possible to accurately determine whether or not the subscriber line loop resistance is determined, which has a remarkable effect on improving the characteristics of such a subscriber line loop resistance determination circuit, and also greatly contributes to improving the quality of voice quality improvement means that utilize subscriber line loop resistance determination. .

[Brief explanation of drawings]

FIG. 1 is a diagram explaining 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, and FIG. 4 is a loop resistance discrimination characteristic diagram of an embodiment of the present invention. 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-----1 to subscriber line 2---1--Power supply circuit 3--1 Measuring resistor 4-1--Power supply voltage measuring means 5-- - Loop current measuring means 6 --- Loop resistance determining means. Diagram: Loop resistance value RL (Ω) Implementation of the present invention Aiki raw diagram for determining the loop nail pile of row A
Diagram Loop resistance value RL (Ω) If L Kurusugi Soba Village's Loop O Taihan 11th Man 11th Soybean Earth Map Figure C

Claims (1)

[Claims] By measuring the loop current I_L supplied to the subscriber line (1) in a closed circuit state from a power supply circuit (2) that supplies DC voltage to the subscriber line (1), The loop resistance value R_L of (1) is the loop resistance value R arbitrarily set in advance.
In the subscriber line loop resistance determination circuit that determines whether the resistance is equal to or greater than _L_O, the resistance value R inserted in one line of the communication line connecting the power supply circuit (2) and the subscriber line (1) is measured. a power supply voltage measuring means (3) that measures the DC voltage V_F output from the power supply circuit (2) and outputs a power supply voltage index βV_F obtained by multiplying the DC voltage V_F by a certain ratio β (β is an arbitrary value). 4), inputting the voltage across the measuring resistor (3) and measuring the loop current I_L flowing through the subscriber line (1), and comparing the loop current I_L and the resistance of the measuring resistor (3); The loop resistance is the product of the values R and the arbitrary loop resistance value R_L_O
Loop current I_L_O and supply voltage V when set to
Loop current index αI_L multiplied by the value α calculated so that αI_L_O・R=βV_F_O for _F_O
・Loop current measurement means (5) that outputs R; the power supply voltage index βV_F outputted from the power supply voltage measurement means (4); and the loop current index αI_L outputted from the loop current measurement means (2). 1. A subscriber line loop resistance discriminating circuit comprising loop resistance discriminating means (6) for inputting and comparing R and sending out an output when one output is larger than the other.