JP3322731B2 - A loop detection method in the subscriber circuit of the exchange. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop detection system in a subscriber circuit of an exchange. The subscriber's circuit of the exchange supplies DC power from the exchange to terminals such as telephones, monitors the state of the loop current (DC loop current) of the subscriber line, and on-hook / off-hooks the terminal (responses at origination and termination). And dial signals (DP signal, PB signal). However, there are cases where the loop detection circuit cannot accurately perform the detection operation due to the connection form of the terminal or the generation of noise induced in the line, and improvement thereof is desired.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram of Conventional Examples 1 and 2, FIG. 12 is a block diagram of Conventional Examples 3 and 4, FIG. 13 is a diagram showing a specific example of a power supply circuit, and FIG. FIG. 15 is a diagram showing a waveform of a supply current or a voltage at the time of an in-phase AC signal.

FIG. And B. In the configurations of Conventional Example 1 and Conventional Example 2 shown in FIG.
And a telephone line TEL by two subscriber lines, a tip line (referred to as T line) and a ring line (referred to as R line).
Is connected to the exchange. A power supply circuit is provided in the subscriber circuit of the exchange, and the T line is connected to the ground through the ground (indicated by G).
The R line is connected to a line-side power supply circuit 100, and the R line is supplied with a power supply (indicated by VBB, generally −48
V is used).

A. In the example, the loop detection circuit 102 is constituted by the R line supply current detection circuit and the filter circuit, and the output is supplied to a scanning circuit (SCN) (not shown) of the control device of the exchange. B. In the example, the loop detection circuit 103 is configured by the R-line power supply voltage detection circuit and the filter circuit.

FIG. 13 shows a specific example of the power supply circuit. The upper circuit corresponds to the T-line power supply circuit 100, and the lower circuit corresponds to the R-line power supply circuit 101. In this circuit, transistors TR1 and TR2 are connected to respective operational amplifiers OP.
1, a control is made so that a constant current flows by the output of OP2 (operational amplifier). Each operational amplifier OP1,
OP2 generates a voltage at the middle point with respect to the change in the voltage state of the T line and the R line, and controls the power supply current to the line. Also, each capacitor C, resistors RT2 to RT5, R
A circuit including a plurality of resistors such as R2 to RR5 is configured to have a high impedance for a differential signal such as an audio signal and a low impedance for an in-phase signal such as another induction signal.

FIG. The loop detection circuit 102 of
The R-line power supply current can be detected by extracting the voltage at the terminal indicated by the symbol "1" which generates a voltage proportional to the current of the emitter of the transistor TR1 in the power supply circuit of FIG. Also,
B. The loop detection circuit 103 can detect the R line supply voltage by extracting the voltage of the terminal indicated by the divided voltage generated by the resistors RR3 and RR4 of the power supply circuit of FIG.

FIG. In the case of the current detection by the above, when a plurality of telephones or the like are connected in parallel to the terminal side, for example, when one telephone number is assigned to a plurality of telephones, one of the telephones turns on / off the DC signal. When the dial (DP dial) is turned off (make break), flyback current flows due to the impedance (mainly inductance L) of the bell circuit of another telephone connected in parallel, and false detection of this flyback current may occur. There is a problem of doing.

This state will be described with reference to an example of an operation waveform of a conventional example shown in FIG. Shows the effect of the flyback current at the time of the DP dial, and shows the waveform of the flyback current in the current detection of the conventional example 1. The flyback current flows when the make breaks, and the current value indicates the threshold voltage. If it exceeds, it is erroneously determined to be a make.

[0009] Further, the in-phase AC signal such as AC induction is applied to a T-line.
When the power supply circuit is guided to the R line, the power supply circuit has a low impedance with respect to the in-phase AC signal.

This situation is shown in FIG. 15. When the in-phase alternating current shown by the solid line is superimposed on the voltage of the T line and the R line between G (ground) and VBB (-48 V), the threshold for loop detection is obtained. A period exceeding the voltage (shown by a bold line in the figure) occurs and erroneous detection occurs. To avoid this, a filter circuit is provided in each loop detection circuit shown in FIG. 11, and the influence of the in-phase alternating current can be reduced by the filter as shown by the dotted line in FIG.

Next, FIG. In the case of Conventional Example 2 (voltage detection) shown in FIG. Since the current level is extremely low as shown in FIG. However, when the loop resistance changes abruptly, there is a problem that the voltage drops and erroneous detection is performed.

[0012] The rapid change of the loop resistance means that, in the case of a dial telephone (DP), the resistance of the transmitter is lost when the DP is transmitted and becomes 0Ω, and the PB telephone (D
In the case of a telephone which generates a TMF signal), the DC resistance increases when a key is pressed. The voltage drop in this case is represented by B. in FIG. The waveforms at the time of impedance change are shown in FIG. This B. The current value shown in (1) slowly falls due to the time constant when the impedance changes, but the voltage value shown in (2) drops instantaneously when the loop is broken and exceeds the threshold voltage.
An erroneous detection occurs as a loop break.

Next, FIG. And B. Conventional example 3 shown in
In the configuration of the conventional example 4, the conventional example 3 includes a T-line power supply current detecting unit and an R-line power supply current detecting unit, and includes a loop detection circuit 104 for adding the outputs of the respective circuits. And a loop detection circuit 105 that includes an R-line power supply voltage detection unit and adds the outputs of the respective circuits.

In the case of the conventional example 3, since the sum of the supply currents of the T line and the R line is detected, even if in-phase AC such as AC induction is induced, the sum of both currents is obtained. The loop detection circuit 104 does not erroneously detect, but detects a flyback current for current detection.

In the case of the conventional example 4, since the sum of the voltages of the T line and the R line is obtained even when an in-phase AC such as an AC induction is induced, the loop detection circuit 105 does not erroneously detect without a filter. However, due to the voltage detection, erroneous detection is performed when the loop resistance changes abruptly.

[0016]

As described above, the prior arts 1 and 3 have a problem of erroneous detection due to a flyback current at the time of a dial pulse, and the prior arts 2 and 4 have a problem due to a sudden change in loop resistance. There was a problem of false detection.

An object of the present invention is to provide a loop detection method in a subscriber circuit of an exchange which can prevent erroneous detection of a flyback current at the time of a dial pulse and erroneous detection at the time of a rapid change in line resistance. I do.

[0018]

FIG. 1 is a first basic configuration diagram of the present invention, FIG. 2 is a second basic configuration diagram of the present invention, FIG. 3 is a third basic configuration diagram of the present invention, and FIG. Is a fourth basic configuration diagram of the present invention, and FIG. 5 is a fifth basic configuration diagram of the present invention.

In FIG. 1, reference numeral 1 denotes a T-line side power supply circuit for supplying power to a subscriber line T line, 2 denotes an R line side power supply circuit for supplying power to a subscriber R line, 3 denotes a loop detection circuit, and 3a denotes a loop detection circuit. An R-line power supply voltage detector, 3b is an R-line power supply current detector, 3c is an adder that generates the sum of the outputs of 3a and 3b, and 3d is a filter circuit.

In each of the circuits shown in FIGS.
Reference numeral 2 denotes the same circuits as those in FIG. 1, and reference numerals 4 to 7 denote loop detection circuits according to the second to fifth principles, respectively. In the loop detection circuit 4 of FIG. 2, reference numeral 4a denotes a T-line power supply current detector, 4b denotes a T-line power supply voltage detector, 4c denotes an adder, and 4d denotes a filter circuit.

In the loop detection circuit 5 of FIG. 3, 5a is a T-line power supply current detector, 5b is an R-line power supply voltage detector, 5c
Is an adder. In the loop detection circuit 6 of FIG. 4, reference numeral 6a denotes a T-line power supply voltage detector, 6b denotes an R-line power supply current detector, and 6c denotes an adder. Next, in the loop detection circuit 7 shown in FIG.
b is a sum detection unit for the supply current of the R / T line, and 7c is an addition unit.

According to the present invention, the loop detection is performed by generating the sum of the power supply voltage and the power supply current from the power supply circuit on the R line side and the power supply circuit on the T line side to one of the lines. Further, the loop detection is performed by generating the sum of the supply current to one line and the supply voltage to the other line. Furthermore, the sum of the supply voltage to one line and the supply current to the other line, and the sum of the supply current to the other line and the supply current to one line are obtained, and the sum of both is generated to detect a loop. Is what you do.

[0023]

In the configuration of FIG. 1, the supply voltage to the R line is detected by the R line supply voltage detector 3a of the loop detection circuit 3, and the supply current to the R line is detected by the R line supply current detector 3b. The sum of the outputs of the two detectors 3a and 3b is generated by an adder 3c. The output signal of the adder 3c is compared with a fixed threshold value (threshold voltage) corresponding to the sum of the voltage and the current (a comparator is not shown) and becomes a loop detection output. The threshold value is set higher than the level in one of the current and the voltage (about 2).
Therefore, flyback current at the time of dial pulse is not detected. Further, even when the loop resistance changes abruptly, since the current and the voltage are summed, when the resistance increases from small to large, the resistances cancel each other out and no erroneous detection is performed. The filter circuit 3d is added to the subsequent stage of the adder 3c when removing the influence of the in-phase AC signal due to the AC induction, and its output is compared with the threshold voltage.

The configuration of FIG. 2 is different from the configuration of FIG. 1 in that the configuration detects the supply voltage and the supply current to the R line, whereas the configuration of FIG. 1 detects the supply voltage and the supply current to the T line. The operation of the loop detection circuit 4 is the same as in FIG. That is, the sum of the respective outputs of the T-line power supply current detector 4a and the T-line power supply voltage detector 4b is generated by the adder 4c and compared with a fixed threshold. The filter circuit 4d is also added when removing the influence of the in-phase AC signal, as in the case of FIG.

Next, in the case of the configuration of FIG.
Indicates the T-line feed current detected by the T-line feed current detector 5a,
The R line supply voltage detector 5b detects the supply voltage of the R line, and the sum of the outputs of the two detectors 5a and 5b is generated by the adder 5c.
The output signal of the adder 5c is compared with a high constant threshold value as in FIG. Also in this case, erroneous detection does not occur even for a rapid change in the flyback current and loop resistance at the time of the dial pulse. In addition, because of the sum of the current on the T line and the voltage on the R line, the in-phase AC signal due to AC induction is canceled out and not detected.

The configuration shown in FIG.
Are the T-line feed voltage detector 6a and the R-line feed current detector 6b
The sum of the outputs of the two detectors 6a and 6b is generated by the adder 6c and compared with a fixed high threshold. The loop detection circuit 6 performs the same operation as the loop detection circuit 5 of FIG. 3 except that the relationship between the voltage and current of the R line and the T line is opposite.

Further, the configuration of FIG.
Calculates the sum of the supply voltage of the T line and the supply voltage of the R line by an R / T line supply voltage sum detector 7a, and calculates the sum of the supply current of the T line and the supply current of the R line by the R / T line supply current. The sum of the two detectors is obtained by an adder 7c. in this case,
As in the case of FIG. 1, erroneous detection is not performed even when the flyback current and the loop resistance suddenly change when a dial is generated. In addition, at the time of AC induction, the in-phase signal cannot be completely removed due to the phase difference between the current and the voltage by the sum of the current of one line and the other line. Since the sum is obtained after completely canceling the common mode signal of the voltage, the influence of the AC induction is eliminated.

[0028]

FIG. 6 is a block diagram of the first embodiment, and FIG. 7 is a diagram showing operation waveforms of the first embodiment. The configuration of FIG. 6 is an embodiment of the loop detection circuit of the first basic configuration diagram of the present invention. In the figure, OP3 and OP4 are operational amplifiers and TR, respectively.
3, TR4 is a transistor, CMP is a comparator, and a filter is composed of a buffer, a resistor R4 and a capacitor C.

The collector of the transistor TR3 and the collector of the transistor TR4 are connected from the ground via the resistor R3, and are input to the filter. It is also possible to configure without using a filter, but in that case, it is input to the comparator CMP. The emitter of the transistor TR3 is connected to a negative power supply (VBB) via a resistor R1, and the emitter of the transistor TR4 is connected to a negative power supply (VBB) via a resistor R2.

With the configuration of FIG. 6, the loop detection circuit 3 of FIG.
, The voltage corresponding to the supply current of the R line is supplied as an input indicated by the operational amplifier OP3, and a signal representing the supply voltage of the R line is supplied as an input indicated by the operational amplifier OP4.

Is generated at the minus terminal of the operational amplifier OP3 due to the imaginary short-circuit of the operational amplifier (op-amp), the signal becomes equal to V1 (the voltage across the resistor R1), and I1 (current flowing through the resistor R1) = V1 / R1
Becomes Is generated at the minus terminal of the operational amplifier OP4 due to the imaginary short circuit of the operational amplifier.
2 (the voltage across the resistor R2), and I2 (current flowing through the resistor R2) = V2 / R2.

The current I3 flowing through the resistor R3 is the sum of the above currents (I1 + I2). When R1 = R2 = R3, the current I3
As the voltage 3, a voltage corresponding to the sum of the supply current of the R line and the supply voltage of the R line is generated.

This signal passes through a filter when it is necessary to remove the in-phase AC signal, and is directly supplied to the comparator CMP when not necessary. Here, a comparison result is output to a scanning circuit (SCN) (not shown) in comparison with a threshold voltage (indicated by Vth) having a value twice as large as that in the case of detecting only one of the voltage and the current.

According to this configuration, the characteristic of the sum of the current and the voltage at the time of the dial pulse is shown in FIG. Since the threshold voltage (Vth) is also set high, As compared with the conventional example shown in FIG.

In addition, even when the loop resistance is suddenly changed, the operation of FIG. As shown in FIG. 14, B. in FIG. Does not cause erroneous detection as in the prior art shown in FIG.

FIG. 8 is a block diagram of the second embodiment, which is an embodiment of the loop detection circuit 4 of the second basic block diagram of the present invention. In this configuration, a negative power supply (VBB) is supplied to the connection point (input to the filter) between the collectors of the transistors TR5 and TR6 via the resistor R7.

Unlike the configuration of the first embodiment, a voltage corresponding to the supply current of the T line is supplied to the input of the operational amplifier OP5, and a signal representing the supply voltage of the T line is supplied to the input of the operational amplifier OP6. You. Is generated at the negative terminal of the operational amplifier OP5 due to the imaginary short-circuit of the operational amplifier, the signal becomes equal to the voltage V5, and the current I5
(Current flowing through the resistor R5) = V5 / R5. Is generated at the negative terminal of the operational amplifier OP6 due to the imaginary short-circuit of the operational amplifier. The signal becomes equal to the voltage V6, and the current I6 (current flowing through the resistor R6) = V6 /
R6.

The current I7 flowing through the resistor R7 is the sum of the above currents (= I5 + I6). When R5 = R6 = R7, the voltage of the resistor R7 is equal to T
A voltage corresponding to the sum of the supply voltages of the lines is generated.

This signal passes through the filter shown in FIG. 8 when it is necessary to remove the in-phase AC signal, and when it is not necessary, it is directly supplied to the comparator COP, where it is detected by only one of the voltage and the current. The comparison result is output to a scanning circuit (SCN) (not shown) in comparison with a threshold voltage (Vth) having a value twice as large as that in the case where the threshold voltage is higher than the threshold voltage (Vth).

FIG. 9 is a block diagram of the third embodiment. This configuration is an embodiment of the loop detection circuit 5 of the third basic configuration (FIG. 3) and the loop detection circuit 6 of the fourth basic configuration (FIG. 4) of the present invention.

The circuit shown in FIG.
In the configuration shown in FIG. 3, a voltage corresponding to the supply current of the T line is supplied to the input 1 and a signal representing the supply voltage of the R line is supplied to the input 2. The signal of input 1 is generated at the output of operational amplifier OP7 (represented by voltage V8), and the signal of input 2 is generated at the negative terminal of operational amplifier OP8 due to the imaginary shortage of the operational amplifier, so that input 2 = voltage V9 and I9 = V9
/ R9. When R8 = R9, the voltage across the resistor R8 becomes V9. As a result, a voltage corresponding to the sum of the supply current of the T line of the input 1 and the supply voltage of the R line of the input 2 is generated at the collector of the transistor TR3. I do.

In the case of this loop detection circuit 5, the signal is directly input to the comparator CMP without passing through a filter and compared with a threshold voltage (Vth). Next, when the fourth loop detection circuit 6 (FIG. 4) is configured by the circuit of FIG. 9, a signal representing the supply voltage of the T line is supplied to the input 1;
The input 2 is supplied with a voltage corresponding to the supply current of the R line.
In this case, the operation is similar to that of the loop detection circuit 5 described above, and T
A voltage corresponding to the sum of the line supply voltage and the supply current of the R line is generated. The output of the sum is directly input to the comparator CMP without passing through a filter, and the threshold voltage (Vth)
Is compared to

FIG. 10 is a block diagram of the fourth embodiment. This configuration is an embodiment of the loop detection circuit 7 having the fifth basic configuration of the present invention shown in FIG. In FIG. 10, operational amplifiers OP7 to OP10 are operational amplifiers to which a voltage corresponding to the power supply voltage or a voltage corresponding to the power supply current is input from the power supply circuit shown in FIG. That is, a voltage corresponding to the supply current of the T line is supplied to the input of the operational amplifier OP7 from the terminal indicated by the symbol in FIG.
13, a voltage corresponding to the supply voltage of the R line is supplied from the terminal indicated by FIG. 13, and a signal representing the sum of the two supply voltages is generated from the collector side of the transistor TR9 and input to the buffer 1.

Also, the input of the operational amplifier OP9 is shown in FIG.
A voltage corresponding to the supply current of the T line is supplied from a terminal indicated by 3 and a voltage corresponding to the supply current of the R line is supplied to the input of the operational amplifier OP10 from the terminal indicated by FIG. Is a transistor TR
It is generated from the collector side of No. 10 and input to the buffer 2.

The two signals of buffer 1 and buffer 2 are
The addition is performed in the addition circuit including the transistor TR1,
A signal representing the result of the addition is input from the collector of the transistor TR11 to the comparator CMP, where it is compared with a threshold voltage (Vth) having a level approximately four times as high as that when comparing the voltage or current value alone.
This comparison result is supplied to the scanning circuit (SCN).

[0046]

According to the present invention, in the loop detection in the subscriber circuit of the exchange, erroneous detection of a flyback current at the time of a dial pulse and erroneous detection at the time of a rapid change in line resistance can be prevented. Further, the third and fourth configurations (the configurations in FIGS. 3 and 4 described above) of the present invention can further prevent erroneous detection due to the in-phase AC signal. Furthermore, the fifth configuration makes it possible to completely eliminate the influence of the in-phase AC signal.

[Brief description of the drawings]

FIG. 1 is a first basic configuration diagram of the present invention.

FIG. 2 is a second basic configuration diagram of the present invention.

FIG. 3 is a third basic configuration diagram of the present invention.

FIG. 4 is a fourth basic configuration diagram of the present invention.

FIG. 5 is a fifth basic configuration diagram of the present invention.

FIG. 6 is a configuration diagram of a first embodiment.

FIG. 7 is a diagram showing operation waveforms of the first embodiment.

FIG. 8 is a configuration diagram of a second embodiment.

FIG. 9 is a configuration diagram of a third embodiment.

FIG. 10 is a configuration diagram of a fourth embodiment.

FIG. 11 is a configuration diagram of Conventional Example 1 and Conventional Example 2.

FIG. 12 is a configuration diagram of Conventional Example 3 and Conventional Example 4.

FIG. 13 is a diagram illustrating a specific example of a power supply circuit.

FIG. 14 is a diagram showing an example of an operation waveform of a conventional example.

FIG. 15 is a diagram showing a waveform of a supply current or a voltage during an in-phase AC signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 T-line side power supply circuit 2 R-line side power supply circuit 3 Loop detection circuit 3a R-line power supply voltage detection part 3b R-line power supply current detection part 3c Addition part 3d Filter circuit

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-241595 (JP, A) JP-A-63-304793 (JP, A) JP-A-1-314093 (JP, A) JP-A 63-304 308496 (JP, A) JP-A-5-219537 (JP, A) JP-A-5-145957 (JP, A)

Claims (6)

(57) [Claims] In a subscriber circuit of an exchange having a T-line power supply circuit and an R-line power supply circuit connected to a T-line and an R-line of a subscriber line, respectively, a feed current detection unit for an R line and an R line Power supply voltage detector and the
Output of R-line power supply current detection unit and detection of R-line power supply voltage
A loop detection method in a subscriber circuit of an exchange, comprising: an adder for generating a sum of outputs from the adders , and comparing a value generated from the adder with a designated threshold to output a loop detection signal. 2. A subscriber line connected to a T line and an R line, respectively.
Of an exchange equipped with a T-line feed circuit and an R-line feed circuit
In the subscriber circuit, a T-line power supply current detector, a T-line power supply voltage detector,
Output of T-line power supply current detection unit and detection of T-line power supply voltage
A loop detection method in a subscriber circuit of an exchange, comprising: an adder for generating a sum of outputs from the adders , and comparing a value generated from the adder with a designated threshold to output a loop detection signal. 3. The subscriber circuit of an exchange according to claim 1 , wherein a filter for attenuating an induced AC component is provided at a stage subsequent to said adding section to prevent erroneous detection by an in-phase AC signal. Loop detection method. 4. A subscriber line connected to a T line and an R line, respectively.
Of an exchange equipped with a T-line feed circuit and an R-line feed circuit
In the subscriber circuit, a T-line feed voltage detecting unit, an R-line feed current detecting unit,
The output of the power supply voltage detector of the T line and the power supply current detector of the R line
An addition unit for generating a sum of the outputs provided, generated from the addition unit
Lulu put the subscriber circuit of the exchange, characterized in that as compared with the specified value of threshold and outputs a loop detection signal <br/>-loop detection method. 5. A subscriber line connected to a T line and an R line, respectively.
Of an exchange equipped with a T-line feed circuit and an R-line feed circuit
In the subscriber circuit, a T-line feed current detecting unit, an R-line feed voltage detecting unit,
The output of the feed current detector of the T line and the feed voltage detector of the R line
An addition unit for generating a sum of the outputs provided, generated from the addition unit
A loop detection method in a subscriber circuit of an exchange, wherein a loop detection signal is output by comparing a value to be performed with a specified threshold value. 6. A subscriber line connected to a T line and an R line, respectively.
Of an exchange equipped with a T-line feed circuit and an R-line feed circuit
In the subscriber circuit, a T-line feed current detecting unit, an R-line feed current detecting unit,
The output of the T line feed current detector and the output of the R line feed current detector
A power supply current sum detector for generating a sum of outputs , a T line power supply voltage detector, an R line power supply voltage detector, and
The output of the T-line power supply voltage detector and the R-line power supply voltage detector
A power supply voltage sum detector that generates a sum of outputs, a power supply current sum detector, and a power supply voltage sum detector.
One of providing an addition unit for generating a sum of the output of the circuit, the pressurized
A loop detection method in a subscriber circuit of an exchange, wherein a loop detection signal is output by comparing a value generated by a calculation unit with a specified threshold value.