JP2999078B2 - Subscriber circuit and subscriber line power supply method - 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 circuit of an electronic exchange, and to a method for supplying power to a telephone terminal of the subscriber.

[0002]

2. Description of the Related Art Conventionally, the setting of the gain of a subscriber circuit of an exchange to which a telephone terminal is connected is fixed or manually set irrespective of the line loss of the connected subscriber line. As a device that automatically optimizes the gain of a subscriber circuit, there is a subscriber circuit described in Japanese Patent Application Laid-Open No. 63-54894.

The above prior art employs a conventional constant resistance and constant voltage power supply method as a power supply method in a subscriber circuit, and the subscriber line resistance changes depending on the line length of the subscriber line connected to the telephone terminal. By changing the call gain in accordance with the DC power supply current flowing to the telephone terminal, the transmission and reception sound volume is automatically optimized.

[0004]

However, the above-mentioned prior art can optimize the transmission and reception volume, but if the subscriber line length is short, the direct current resistance of the subscriber line becomes small, so that the telephone terminal can be used. There is a problem in that the flowing DC supply current increases and the power consumption in the subscriber circuit on the power supply side increases. This becomes a hindrance to thermal problems such as heat radiation in implementing the miniaturization and weight reduction of the subscriber circuit, and it is necessary to reduce power consumption in the subscriber circuit.

As a countermeasure against the above-mentioned thermal problem, a method of changing a power supply method from a constant resistance constant voltage power supply method to a constant current power supply method is considered. However, simply changing the power supply method to the constant current power supply method does not operate the circuit (usually called a pad) for adjusting the audio signal level by the power supply current built in the telephone terminal, and the There is a problem that the attenuation of the voice signal due to the line length cannot be compensated on the telephone terminal side.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a subscriber circuit which automatically makes a signal transmission gain constant irrespective of the subscriber line length and reduces power consumption in the subscriber circuit.

[0007]

In order to achieve the above object, a subscriber circuit connected to a terminal via a subscriber line for inputting / outputting a signal includes a constant current power supply circuit for supplying DC power with a constant current. A termination circuit that is provided between the input side and the output side of the signal and determines the impedance of the subscriber circuit, wherein the termination circuit is configured such that the combined impedance of the subscriber line and the subscriber circuit is previously determined. The transmission coefficient of the termination circuit is variably set so as to have a determined impedance.

[0008] A DC detection circuit for detecting a DC voltage generated by the constant current feeding circuit is further provided, and the termination circuit sets a transfer coefficient of the termination circuit in accordance with an output voltage of the DC detection circuit.

Further, in an exchange provided with one or more subscriber circuits connected to a terminal via a subscriber line and for inputting / outputting a signal, the subscriber circuit includes a constant-current power supply circuit for supplying DC power at a constant current. And an audio signal output circuit that outputs an audio signal to the subscriber line, an audio signal detection circuit that detects an audio signal generated in the subscriber line, and between the audio signal detection circuit and the audio signal output circuit. And a termination circuit for determining the impedance of the subscriber circuit,
The terminating circuit sets a transmission coefficient of the audio signal detected by the audio signal detection circuit so that the impedance between the subscriber line and the subscriber circuit becomes a predetermined impedance, and outputs the audio signal. The setting of the transfer coefficient of the audio signal output from the circuit can be performed.

[0010]

The DC communication current from the subscriber circuit to the telephone terminal is made constant regardless of the length of the subscriber line because it is performed at a constant current.
By setting the DC communication current value at the maximum length of the subscriber line to be the minimum value of the DC communication current in the constant-resistance and constant-voltage power supply system, power consumption can be reduced.

For example, if the subscriber line length is zero and the DC resistance on the telephone terminal side is 50 Ω in the -48 V, 440 Ω constant voltage constant resistance power supply system, the DC power supply current is about 1 Ω.
00 mA, the power consumption on the subscriber circuit side is about 4 W. If this is supplied at a constant current of about 25 mA, the power consumption on the subscriber circuit side can be reduced to about 1.2 W (about ３), and a heat sink required for the power supply circuit of the electronic subscriber circuit. From the point of view, it is possible to reduce the size and weight by reducing the power consumption.

The reason why the audio signal level is controlled to be constant irrespective of the subscriber line length is that the DC detection circuit obtains the line length by measuring the voltage between the subscriber lines, and the line is provided in the terminal circuit. Control can be performed by compensating for the increase or decrease in the subscriber line impedance corresponding to the length, or by determining the terminal impedance of the subscriber circuit so as to correct the increase or decrease in the audio signal level due to the subscriber line impedance. The voltage between the subscriber lines is measured by the DC detection circuit because the DC communication current is supplied at a constant current, so that the voltage between the subscriber lines on the subscriber circuit side is proportional to the line length of the subscriber line. Is changed.

When the transmission coefficient of the termination circuit is changed, the transmission coefficient is selected so that the combined impedance of the termination impedance of the subscriber circuit and the impedance of the subscriber line is constant as the transmission coefficient of the termination circuit. By increasing or decreasing the line length obtained from the voltage between the subscriber lines for the transfer coefficient for realizing the impedance of the subscriber line, the apparent subscriber line length from the telephone terminal side is made constant. Works like that. Thus, even if the actual subscriber line length changes, the apparent subscriber line length is always constant, so that the audio signal level can be kept constant.

Further, the transmission coefficient on the exchange side may be changed. In this case, the transmission / reception signal level on the exchange side is operated so as to correct the increase / decrease of the audio signal level due to the impedance of the line length of the subscriber line obtained from the voltage between the subscriber lines. Can be kept constant.

As described above, the DC communication current to the telephone terminal is fed by the constant current circuit, and the DC detection circuit for detecting the DC voltage between the subscriber lines, and the output voltage of the detection circuit on the subscriber circuit side. By providing a terminating circuit that varies the terminating impedance, or by changing the transfer coefficient on the exchange side, the power consumption on the subscriber circuit side is reduced, and the voice signal level is automatically adjusted regardless of the line length. Can be kept constant.

[0016]

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a configuration diagram of a subscriber circuit in one embodiment of the present invention. FIG. 3 shows an equivalent circuit of the subscriber circuit.

In FIG. 1, a subscriber circuit 9 is connected to the subscriber line 2, supplies a constant current to the telephone terminal 1, and adjusts a transfer coefficient in accordance with an actual line length by a terminating circuit 7, thereby providing a pseudo-circuit. A part of the subscriber line is realized in the subscriber circuit, and the length of the subscriber line from the telephone terminal, that is, the resistance is equivalently fixed, and the subscriber line is connected to the input of the voltage-current conversion circuit 4.

In the subscriber circuit 9, the constant current circuit 3
Performs constant current power supply. The voltage-current conversion circuit 4 is an audio signal output circuit that sends an audio signal component to the telephone terminal. The differential voltage detection circuit 5 is an audio signal detection circuit that detects an audio signal component on the telephone terminal side. The DC voltage detection circuit 6 detects a DC voltage between two lines of the subscriber line. The termination circuit 7 varies the transfer coefficient in accordance with the DC voltage between the two lines detected by the DC voltage detection circuit 6. The power supply 8 is a power supply for the subscriber circuit.

In FIG. 1, a subscriber line 2 connected to a telephone terminal 1 has a constant current circuit 3, an input of a DC voltage detection circuit 6, an output of a voltage / current conversion circuit 4, and a differential voltage detection circuit. 5 input. An output signal of the differential voltage detection circuit 5 and a signal v _4WR sent from the exchange side to the telephone are added and input to an AC signal input of the termination circuit 7, and the output signal of the termination circuit 7 is Are connected so as to become an input signal of the voltage-current conversion circuit 4 and a signal v _4WS sent from the telephone terminal 1 to the exchange. An output signal of the DC voltage detecting circuit 6 is connected to a control input for controlling a transfer coefficient of the terminating circuit 7.

When DC power is supplied by the constant current source 3 connected to the subscriber line 2, the DC voltage generated between the two lines of the subscriber line 2 on the subscriber circuit side is equal to the DC resistance of the telephone terminal 1 and the subscriber. This is a voltage drop with respect to the DC resistance of the line. Assuming that the subscriber line has a resistance that increases in proportion to the line length L as shown in FIG. 2, the line resistance is R _Line (L),

[0021]

(Equation 1)

If the DC voltage between the lines is V _L , V _L is given by the following equation.

[0023]

(Equation 2)

Here, R _TEL is the DC resistance of the telephone terminal 1, R _L0 is the line resistance per unit length of the subscriber line, L is the line length of the subscriber line, and I _L is the current of the constant current source 3. Value.

Therefore, the line length L of the subscriber line 2 can be obtained by detecting the DC voltage _VL generated in the subscriber line 2 by the DC voltage detection circuit 6.

In FIG. 1, if the transfer coefficient of the differential voltage detection circuit 5 of the subscriber circuit 9 is A, the transfer coefficient of the voltage-current conversion circuit 4 is G, and the transfer coefficient of the termination circuit 7 is β (V _L ). ,
The terminating impedance Z _in (V _L ) of the subscriber circuit 9 is as follows.

[0027]

(Equation 3)

As shown in FIG. 3, as the terminating impedance of the subscriber circuit 9, in addition to the terminating impedance required for the subscriber circuit 9 by the resistor R _S and the capacitor C _S , the voltage V _L between the subscriber lines is used. , The impedance R _X (V _L ) equivalent to that of the subscriber line 2 is realized equivalently, and the termination impedance Z
_in (V _L ).

[0029]

(Equation 4)

[0030] Here, the sum of the impedance component R _X to equivalently implement (V _L) conditions as connected subscriber line 2 of the impedance R _Line of (L), determined in advance as shown in Equation 5 The constant value R _Lall is set.

[0031]

(Equation 5)

As described above, the total impedance of the subscriber line based on the impedance R _Line (L) of the subscriber line 2 and the subscriber line impedance R _X (V _L ) equivalently realized by the subscriber circuit 9. Is constant,
The impedance component of the apparent subscriber line length from the subscriber terminal 1 is always constant regardless of the line length L of the subscriber line 2. The transfer coefficient β (V
_L ) is obtained by the following equation 6 from equations 2-5.

[0033]

(Equation 6)

Here, R _S1 , R _S2, and C _S ′ are arbitrary constants that determine the termination impedance R _S , C _S inherent to the subscriber's circuit.

The transmission coefficient β of the termination circuit 7 shown in equation (6)
According to (V _L ), the apparent terminal impedance Z _in ′ on the subscriber circuit side including the subscriber line 2 viewed from the telephone terminal end is always a constant value Z _const as in the following equation.

[0036]

(Equation 7)

FIG. 4 shows a specific circuit configuration of an equivalent circuit of the termination circuit 7 shown in FIG. FIG. 5 shows an equivalent circuit of the voltage control termination circuit. As shown in FIG. 5, in the voltage control termination circuit, the resistance R _X ′ is changed by the output voltage V _CONT from the DC voltage detection circuit 6, and the output current is thereby changed. FIG. 4 is a configuration example of the termination circuit 7 for realizing the transfer function β (V _L ) in Expression 7. 11 is a voltage controlled resistor R _X '(V _CONT), can be used to adjust the resistance value by the control voltage V _CONT, the transistor Q ₁ to Q _12, resistors R ₁ ~
It is composed of R ₃ , _RE and a current source I ₁ . 12 is a current output circuit, formed by transistors Q ₁₃ to Q ₁₄ and the current source I _2, a current mirror circuit for outputting a current that flows in the voltage control resistor 11. 13 is an input terminal of the termination circuit 7, 14 is an output terminal of the termination circuit 7, and 15 is an input terminal for inputting a control input voltage V _CONT that changes a transfer coefficient of the termination circuit. The voltage control resistor R _X ′ (V
_CONT ) is given by the following equation (8) if the resistors R _{1 to} R ₃ have the same resistance value and the transistors Q _{1 to} Q ₃ , Q ₄ and Q ₅ , Q _{6 to} Q ₁₀ , and Q ₁₁ and Q ₁₂ have the same characteristics. The resistance value can be varied by the control input voltage V _CONT as shown by.

[0038]

(Equation 8)

Here, V _T = about 26 mV. Therefore, the transfer coefficient β (V _CONT ) of the termination circuit 7 in FIG.
Is as shown in Equation 9 below.

[0040]

(Equation 9)

Here, in order to make Equation 9 equal to Equation 7, the variable range of the voltage control resistor R _X ′ (V _{CON T} ) is set to R _X ′ _{(MIN) to} R _X ′ _(MAX) . Then, the transfer coefficient β (V _L ) of the termination circuit 7 can be realized such that V _CONT and R _S1 ′ are represented by the following equations (10) and (11).

[0042]

(Equation 10)

[0043]

[Equation 11]

As described above, the voltage between the subscriber lines corresponding to the resistance due to the actual line length of the subscriber line is measured, the transfer coefficient of the termination circuit in the subscriber circuit is varied, and the apparent value is determined. Keep the line resistance constant.

In the conventional example, if the telephone terminal 1 is simply supplied with direct current at a constant current, the audio signal level adjustment circuit such as a pad circuit inside the telephone terminal 1 does not operate, and the audio signal is attenuated. In this embodiment, DC power is supplied to the telephone terminal 1 with a constant current. However, since the transfer coefficient is varied as described above, the transmission gain of the audio signal becomes constant as described below. That is, the transmission gain G ₂₄ from the exchange to the telephone terminal and the transmission gain G from the telephone terminal to the exchange
₄₂ is as follows. The voltage of the AC signal at the telephone terminal v _2W ', when the voltage of the AC signal sent to the exchange side and v _4WS, v _2W' relationship between v _4WS is as shown in the following equation,

[0046]

(Equation 12)

Here, R _Line (L) + Z _in (V _L ) is
It is controlled by the termination circuit 7 so that it becomes a constant value Z _const , Z _in (V _L ) becomes as shown in Expression 3, and the transmission gain G ₂₄ becomes constant as shown in Expression 13.

[0048]

(Equation 13)

Next, _assuming that an AC signal sent from the exchange side is v _4WR , an AC voltage on the subscriber circuit side of the subscriber line is v _2W , and an impedance of the telephone terminal 1 is Z _TEL , v _4WR and v _2W The relationship is as follows:

[0050]

[Equation 14]

[0051] Here, the relationship of the phone terminal-side AC signal v _2W 'and the AC signal v _2W of the subscriber circuit side,

[0052]

(Equation 15)

Is as follows. Thus, the transmission gain G ₄₂ is constant as shown in Equation 16 from the number 14 and number 15.

[0054]

(Equation 16)

As described above, the DC communication current to the telephone terminal 1 is supplied by the constant current circuit 3 to detect the DC voltage between the subscriber lines, and the subscriber circuit is detected by the output voltage of the detection circuit 6. By providing the terminating circuit 7 for varying the terminating impedance on the side, the transmission gains G ₂₄ and G ₄₂ can be automatically kept constant regardless of the line length, and the audio signal level can be kept constant.

In this embodiment, as described above, the termination circuit 7
Thus, a part of the subscriber line is artificially realized in the subscriber circuit corresponding to the actual line length, and the length of the subscriber line from the telephone terminal is equivalently made constant. For this reason, it is possible to use constant current power supply as a DC power supply method from the subscriber circuit side. In the conventional constant-resistance and constant-voltage power supply, to meet the maximum subscriber line length at which the supply current is minimum,
By selecting each of the subscriber line impedance and the supply current to be realized in the subscriber circuit, it is possible to reduce the power consumption of the subscriber circuit. Since the power consumption on the subscriber circuit side is reduced, the heat radiating plate required for heat radiation of the electronic power supply circuit can be reduced, and the subscriber circuit can be reduced in size and weight.

Further, as the constant current feeding circuit 3, DC /
When a power conversion circuit such as a DC converter is used, power consumption can be further reduced.

FIG. 6 shows a second configuration example of the termination circuit 7 of the present embodiment. In the above description, for the sake of simplicity, the subscriber line 2 is assumed to have only a resistor as shown in FIG. 2, but an actual subscriber line has a C line between the subscriber lines as shown in FIG. _AB is represented by a distributed constant circuit in which the capacitances of C _AG and C _BG exist between the ground and the ground. Therefore, a more complicated function is required as the transfer function β (V _L ) of the termination circuit 7 than the equation (7). Therefore, digital signal processing (DS
P) realizes the termination circuit 7 and can perform signal processing. The voltage V _CONT of the output signal 15 from the DC voltage detection circuit 6 and the audio signal of the output signal 13 from the differential voltage detection circuit 5 are converted into digital values by an AD converter, and the equation shown in Expression 7 and the capacitance are converted. Is processed by digital signal processing (DSP) according to the equation in consideration of the above, and an audio signal as a processing result is output.

The above-mentioned subscriber circuit detects the audio signal voltage of the subscriber line 2 by the differential voltage detecting circuit 5 as a method of terminating the audio signal, and outputs the subscriber line 2 by the voltage-current conversion circuit 4 through the terminating circuit 7. Is a subscriber circuit of a voltage detection current supply system for supplying a voice signal to the subscriber line. The termination method according to the present embodiment detects a current of a voice signal flowing through the subscriber line 2 and outputs a voltage to the subscriber line 2 through the termination circuit. The present invention can also be realized in a current detection voltage output method.

Next, a second embodiment will be described. FIG.
FIG. 7 is a configuration diagram of a subscriber circuit according to a second embodiment of the present invention. The subscriber circuit in the second embodiment is different from the DC voltage detection circuit 6 in FIG. 1 in that a DC voltage detection circuit 2 for detecting a DC voltage from the output of the differential voltage detection circuit 5 is used.
1, a voltage source 20 for setting a power supply current value is provided in place of the constant current circuit 3 for supplying power to the subscriber circuit, and is added to an output signal of the termination circuit 7 for determining a termination impedance,
This is a subscriber circuit connected to the input of the voltage-current conversion circuit 4.

In FIG. 1, the DC voltage detecting circuit 6 detects the DC voltage _VL generated between the subscriber lines by performing a balanced / unbalanced conversion directly from the subscriber line side. In this example, the differential voltage between the subscriber lines is balanced / unbalanced converted by the differential voltage detection circuit 5, and then the DC voltage is detected. Thus, the circuit required for the DC voltage detection circuit can be realized by a simple CR filter using a resistor and a capacitor as shown in FIG. 9 as an example of the configuration. In addition, when implemented in operating amplifier 22 and the transistor 23 as shown in FIG. 10 as an example of the configuration of the circuit of the voltage-current conversion circuit 4 (showing the discharge side of the current.), The supply current is used as a bias current of the transistor By doing so, the circuit can be simplified.

Further, it is possible to reduce a high withstand voltage circuit required on the subscriber line side to which a high voltage such as lightning is applied, and to simplify the circuit.

Next, a third embodiment will be described with reference to FIG. A subscriber line 2 connected to the telephone terminal 1 receives an input of a constant current circuit 3 for supplying a constant current and a DC voltage detection circuit 6 for detecting a DC voltage between two lines of the subscriber line, and an audio signal component. The output of the voltage-current conversion circuit 4 serving as an audio signal output circuit to be transmitted to the telephone terminal side and the input of a differential voltage detection circuit 5 serving as an audio signal detection circuit for detecting an audio signal component on the telephone terminal side are connected. The termination circuit 70 is different from the termination circuit described above, and can be configured by a conventional termination circuit. The output of the differential voltage detection circuit 5 is connected to the input of the termination circuit 70 and the input of the gain adjustment circuit 32 for adjusting the audio level of the signal _v4WS transmitted to the exchange, and the signal transmitted from the exchange. v _4WR is input to the gain adjustment circuit 31, added to the output of the gain adjustment circuit 31 and the output of the termination circuit 70, and connected so as to be input to the voltage-current conversion circuit 4. The output of the DC voltage detection circuit 6 is
The gain control circuits 31 and 32 are connected to gain control inputs. The power supply 8 is a power supply for the subscriber circuit.

In this embodiment, as in the first embodiment, DC power is supplied by the constant current circuit 3 and the DC voltage detection circuit 6
2 is obtained as the output voltage, the line length L of the subscriber line 2 can be obtained, and the impedance R _Line (L) of the subscriber line 2 can also be obtained.

Similarly, in FIG. 11, if the transfer coefficient of the differential voltage detection circuit 5 of the subscriber circuit 9 is A, the transfer coefficient of the voltage-current conversion circuit 4 is G, and the transfer coefficient of the termination circuit 70 is β, The terminating impedance Z _in of the subscriber circuit 9 is given by Equation 17
It becomes the value shown in.

[0066]

[Equation 17]

In the present embodiment, unlike the first embodiment, the transmission impedance of the termination circuit 70 is not changed, so that the termination impedance Z _in shown in Expression 17 is always constant.

Since the telephone terminal 1 is supplied with a constant current, the pad circuit inside the telephone terminal 1 does not operate as in the first embodiment, and the terminal impedance Z _in of the subscriber circuit 9 is maintained.
Is fixed as shown in Expression 16, and if the line length L and the impedance R _Line (L) of the subscriber line 2 are obtained,
It is possible to obtain the attenuation of the voice signal transmission between the subscriber terminal 1 and the subscriber circuit 9 by the subscriber line 2. Therefore, the gain adjustment circuit 31 is controlled so as to correct this attenuation.
And 32, the transmission gain between the exchange side and the subscriber terminal 1 can be made constant regardless of the line length.

FIG. 12 shows an example of the configuration of the gain adjustment circuits 31 and 32. By changing the control voltage V _CONT by changing the control voltage V _{CONT based} on the voltage division of the voltage control resistor 11 and the fixed resistor _RY used in the configuration example of the voltage control termination circuit shown in FIG. , The gain can be adjusted.

As described above, according to the present embodiment, regardless of the subscriber line length, the resistance of the terminal impedance can be made constant, the power can be supplied to the telephone terminal by the constant current circuit, and the current of the constant current circuit can be reduced. By reducing the value, power consumption associated with power supply on the subscriber circuit side can be reduced. For this reason, thermal problems such as heat radiation are reduced, and high-density mounting, small size, light weight, and thinness of the subscriber circuit can be achieved.

[0071] As shown in the above embodiments, the audio signals before and after the output of the terminal circuit 7 v _4WR, v _{4 WS} injection point, for the removal point, not limited to this, the gain adjustment circuit 31,3
It goes without saying that the circuit configuration of No. 2 is not limited to this.

As described above, in the method of changing the transfer coefficient of the termination circuit, the subscriber line is simulated in the subscriber circuit, and equivalently, the impedance of the subscriber circuit viewed from the telephone terminal side is fixed. Therefore, the transmission gain of the audio signal can be made constant irrespective of the subscriber line length.

Further, in the method using the gain adjusting circuit, the attenuation due to the impedance of the subscriber line is corrected for the level of the voice signal transmitted / received to / from the exchange, so that it can be kept constant irrespective of the subscriber line length. For this reason, power can be supplied to the telephone terminal by the constant current circuit, and the current consumption of the subscriber circuit can be reduced by reducing the current value of the constant current circuit. For this reason, thermal problems such as heat radiation are reduced, and high-density mounting, small size, light weight, and thinness of the subscriber circuit can be achieved.

The line length is obtained from the DC voltage, and the transmission coefficient of the termination circuit or the transmission coefficient of the transmission / reception signal is automatically varied. The transmission gain can be kept constant regardless of the line length of the subscriber line. It is possible to supply DC power by current and reduce power consumption.

[0075]

According to the present invention, the transmission gain of a voice signal is automatically made constant irrespective of the subscriber line length, and the power consumption in the subscriber circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a subscriber circuit according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit 1 of a subscriber line.

FIG. 3 is an equivalent circuit at the end of a subscriber circuit.

FIG. 4 is a configuration diagram of a voltage control termination circuit.

FIG. 5 is an equivalent circuit of a voltage control termination circuit.

FIG. 6 is a configuration diagram of a voltage control termination circuit.

FIG. 7 is an equivalent circuit 2 of a subscriber line.

FIG. 8 is a principle diagram of a subscriber circuit according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a DC voltage detection circuit.

FIG. 10 is a configuration diagram of a voltage-current conversion circuit.

FIG. 11 is a diagram illustrating the principle of a subscriber circuit according to a third embodiment of the present invention.

FIG. 12 is a configuration diagram of a gain adjustment circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Telephone terminal, 2 ... Subscriber line, 3 ... Constant current circuit, 4
... voltage-current conversion circuit, 5 ... differential voltage detection circuit, 6 ... DC voltage detection circuit, 7/70 ... termination circuit, 8 ... power supply, 9 ... subscriber circuit, 11 ... voltage control resistor, 12 ... current output circuit,
13 input terminal, 14 output terminal, 15 control input terminal, 16 current mirror circuit, 20 power supply, 21
DC voltage detection circuit, 22: operational amplifier, 23: transistor, 31: gain adjustment circuit, 32: gain adjustment circuit. C _AB
… The line capacity of the subscriber line per unit length, C _AG … the ground capacity of the subscriber line per unit length, C _BG … the ground capacity of the subscriber line per unit length, R _Line (L)… Line resistance at subscriber line length L, R _L0 ... line resistance per unit length, V _L ... DC voltage between subscriber lines on the subscriber circuit side,
V _BB ... power supply, v _2W ... AC voltage between subscriber lines on the subscriber circuit side, v _2W '... AC voltage between subscriber lines on the telephone terminal side, v _4WS ... AC signal sent to the exchange side, v _4WR : AC signal sent from the exchange side, C _S : Capacitance component of terminal impedance, C _S ': Capacitance for determining terminal impedance, R _S : Resistance component of terminal impedance, R _S1 : Resistance for determining terminal impedance, R _S2 ... A resistor for determining the terminal impedance, R _X ... For the subscriber line impedance equivalently realized in the subscriber circuit, and R _X ′... Determine the subscriber line impedance equivalently realized in the subscriber circuit. Resistance, R _Y ... resistance, V _CC ... power supply, V _EE ... power supply, Q ₁
ＱQ ₁₆ト ラ ン ジ ス タ transistor, R ₁ ＲR ₃抵抗 resistance, I _{1 ＩI 2} 2current source.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akira Ishizawa 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-60-28365 (JP, A) JP-A Sho 61-57165 (JP, A) JP-A-62-155692 (JP, A) JP-A-58-77361 (JP, A) JP-A-60-117989 (JP, A) JP-A-61-41265 (JP, A) A) JP-A-57-154966 (JP, A) JP-A-63-169864 (JP, A) JP-A-62-69795 (JP, A) JP-A-63-54894 (JP, A) JP-A-63 JP-A-15591 (JP, A) JP-A-63-269861 (JP, A) JP-A-4-213261 (JP, A) JP-A-63-122394 (JP, A) JP-A-61-108231 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H04Q 3/42-3/42 107 H04M 19/00-19/08

Claims (3)

(57) [Claims] 1. A subscriber circuit connected to a terminal via a subscriber line and inputting / outputting a signal, a constant current feeding circuit for supplying DC power at a constant current, and a detection device for detecting a voltage between the subscriber lines. Circuit, and the terminal of the subscriber circuit according to the voltage detected by the detection circuit so that the combined impedance of the subscriber line and the subscriber circuit becomes a predetermined impedance.
A termination circuit for changing an end impedance. 2. A subscriber circuit connected to a terminal via a subscriber line and inputting / outputting a signal, wherein a voltage source for setting a supply current value and a differential voltage between the subscriber lines are detected. Differential voltage
A detection circuit that detects a DC voltage from the subscriber circuit, and the subscriber circuit according to the voltage detected by the detection circuit so that the combined impedance of the subscriber line and the subscriber circuit becomes a predetermined impedance. End
A termination circuit for changing an end impedance. 3. A subscriber line power supply method in a subscriber circuit connected to a terminal via a subscriber line and inputting / outputting a signal, wherein a voltage between the subscriber lines is detected, and Changing the termination impedance of the subscriber circuit according to the voltage detected by the detection circuit so that the combined impedance with the subscriber circuit becomes a predetermined impedance, and performing DC power supply with a constant current. Characteristic subscriber line power supply method.