JPH0989971A - Method and device for judging presence of disconnection of subscriber's line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for judging presence of disconnection of a subscriber's line and a device in which the presence of a disconnection can be judged even when a line capacity is large, and the threshold voltage can be easily set even when the fluctuation of voltage of the subscriber's line is taken into consideration. SOLUTION: Lines A and B are subscriber's lines, and a modular jack (MJ) 41 is connected between these subscriber's lines. A line capacity CAB is present between the subscriber's lines A, B. A disconnection presence judging device, which is provided within a station, is formed of switches 11-15, a detecting resistor 21, and a comparator 31. A voltage -VBB is first applied between the lines A, B through the resistor 21 by the switches 13, 14, and a voltage +VBB is then applied between the lines A, B through the resistor 21 by the switches 11, 12. The time until the potential of the line A becomes a threshold voltage Vth is measured. This time is long when the MJ 41 is present, and short when it is absent, whereby the presence or absence of a disconnection (the presence or absence of the Mj 41) can be judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber line disconnection presence / absence determining method and device used for determining the presence / absence of disconnection of a subscriber line (presence / absence of a modular jack).

[0002]

2. Description of the Related Art FIG. 4 shows the structure of a conventional subscriber line disconnection presence / absence determining device. In this figure, the broken line H shows the disconnection presence / absence determining device provided in the station, and the left side shows the subscriber line. In this figure, the line B is connected to GND, and the voltage VBB is applied to the line A through a detection resistor 21 (resistance value: R). The switch 11 is connected between the A line and the B line on the subscriber circuit side in the station. Comparator 3
Reference numeral 1 is a comparator for detecting the rising of the potential V1 of the A line, one input terminal of which is connected to the A line and the threshold voltage Vth is applied to the other input terminal. The comparator 31 outputs an output voltage V2 of "L" (low) if the potential V1 of the A line is smaller than the threshold voltage Vth and "H" (high) if it is greater than the threshold voltage Vth. It can be considered that an equivalent line capacitance CAB between the A line and the B line is connected between the A line and the B line on the subscriber line side. Further, a modular jack (hereinafter referred to as MJ) 41 including a resistance Rmj and a capacitance Cmj is connected between the A line and the B line. The MJ 41 serves as an interface between a terminal device (not shown) and subscriber lines (A and B lines), and is not connected when the subscriber line is an empty line.
That is, when the subscriber line is an empty line, the line A-B is disconnected.

Next, the presence / absence of disconnection of the subscriber line (MJ
The operation of the presence / absence determining device will be described with reference to FIGS. 4 and 5. In FIG. 4, first, the switch 11 is turned on, the charge between the line A and the line B is discharged, and then the switch 11 is turned off. Then, as shown in FIG. 5, the potential V1 of the line A is at the GND level (0 V). ) To a voltage VBB, and the output voltage V2 of the comparator 31 is "H" (high) when V1> Vth and "1" when V1 <Vth.
Then, the line capacitance between the A line and the B line is obtained by obtaining the time t from the fall of the switch 11 to the fall of the output voltage V2 using the characteristic shown in FIG. You can know.

Next, the waveform of the potential V1 of the A line and the output voltage V2 of the comparator 31 when only the line capacitance CAB is connected to the subscriber line and when the line capacitance CAB and MJ41 are both connected. Is shown in FIG. In this figure, when only the line capacitance CAB is connected to the subscriber line, the potential V
1 rises at a fast speed from 0V to voltage VBB based on the time constant (τ = CAB · R) between the line capacitance CAB and the resistance value R of the detection resistor 21.

On the other hand, the line capacities CAB and MJ41 are connected to the subscriber line.
When they are connected together, the potential V1 rises quickly from 0V to the potential VBB × Rmj / (Rmj + R), and thereafter rises slowly to the voltage VBB. This is MJ
By the resistance Rmj of 41 (see FIG. 4), the capacitance C
Because mj is less likely to be charged.

As described above, there are differences in the waveforms of the potential V1 and the output voltage V2 when the line capacitance CAB is connected to the subscriber line and when the line capacitance CAB and the MJ41 are both connected. I understand. Therefore, the threshold voltage Vth of the comparator 31 is set to the potential VBB × Rmj / (Rmj + R) and the voltage Vth.
If set between BB and the line capacitance CAB, the rise time t1 when only the line capacitance CAB is connected and the line capacitances CAB and MJ are set.
There is a difference from the rising time t2 when 41 is connected, and the presence or absence of disconnection (presence or absence of MJ41) can be determined from this difference.

[0007]

In the above-described conventional subscriber line disconnection presence / absence determining device, when the line capacitance CAB is small, only the line capacitance CAB is connected to the subscriber line and the line capacitance CAB is connected to the subscriber line. There is a difference in the time (t1, t2) measurement results when CAB and MJ41 are connected together, and it is possible to determine the presence or absence of disconnection. However, if the line capacitance CAB is large, there is a clear difference in the above time measurement results. Will not occur,
There is a drawback that it is difficult to determine whether or not there is a disconnection.
Further, considering the fluctuation of the voltage VBB, etc., the threshold voltage Vth
There is a problem that it is difficult to set the voltage between the potential VBB × Rmj / (Rmj + R) and the voltage VBB. The present invention has been made under such a background. Even when the line capacitance is large, it is possible to determine the presence / absence of a disconnection, and it is possible to easily adjust the threshold voltage even if voltage fluctuation is taken into consideration. It is an object of the present invention to provide a method and apparatus for determining the presence or absence of disconnection of a subscriber line that can be set to.

[0008]

According to a first aspect of the present invention, there is provided a disconnection presence / absence determining method for determining the presence / absence of a disconnection between first and second subscriber lines. Apply a DC voltage for a certain period of time through a resistor between the wires, then
The DC voltage is applied between the first and second subscriber lines via a resistor by changing the polarity, the change state of the voltage between the subscriber lines is measured, and the presence or absence of disconnection is determined based on the measurement result. It is characterized by making a distinction.

According to a second aspect of the present invention, in the method for determining the presence / absence of disconnection of the subscriber line according to the first aspect, the change state of the voltage between the subscriber lines is measured in advance by measuring the voltage between the subscriber lines. It is characterized by measuring the time to reach the specified reference voltage.

According to a third aspect of the invention, in a disconnection presence / absence determining device for determining the presence / absence of a disconnection between the first and second subscriber lines, one end is connected to a DC power source and an output end of the DC power source. And a voltage at the other end of the resistor and a ground potential are applied to the first and second subscriber lines, respectively, and a voltage at the other end of the resistor and a ground potential are respectively applied to the second and first subscriber lines. The switching means for applying to the subscriber line and the comparing means for comparing the voltage at the other end of the resistor with the reference voltage and outputting a coincidence detection signal when the both coincide with each other. It is characterized in that the presence or absence of disconnection between the first and second subscriber lines is determined based on the above.

According to a fourth aspect of the present invention, in the subscriber line disconnection presence / absence determining device according to the third aspect, the reference voltage is the power supply voltage VBB, the resistance value is R, the first and the first values are the first and the second. When the resistance value of the modular jack connected to the second subscriber line is Rmj, it is set to a value between the voltage {2 × VBB × Rmj / (Rmj + R)}-VBB and the voltage VBB. I am trying.

[0012]

According to the first aspect of the present invention, first, a direct current voltage is applied between the first and second subscriber lines through a resistor for a certain period of time or more, whereby the capacitance existing between the subscriber lines. To charge. Next, the DC voltage is applied between the first and second subscriber lines through a resistor while changing the polarity. As a result, the voltage change between the first and second subscriber lines becomes twice the DC voltage. Next, the change state of the voltage between the subscriber lines (the change state of the voltage due to the discharge of the capacitance) is measured. This voltage change is due to the electric charge charged in the capacitance between the subscriber lines being discharged through the resistor. Therefore, when the subscriber lines are not disconnected, that is, when the modular jacks are connected between the subscriber lines, the capacity of the modular jacks increases the discharge time. On the other hand, when the modular jack is not connected between the subscriber lines, the discharge time becomes short. That is, it is possible to determine the presence or absence of disconnection based on the change state of the voltage between the subscriber lines.

According to the second aspect of the present invention, the change state of the voltage between the subscriber lines is measured by measuring the time until the voltage between the subscriber lines reaches a predetermined reference voltage. Done by.

The invention described in claims 3 and 4 is an apparatus for carrying out the method according to the invention described in claims 1 and 2, and its operation is as described above.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a subscriber line disconnection presence / absence determining device according to an embodiment of the present invention. In this figure, parts corresponding to those in FIG. 4 are assigned the same reference numerals and explanations thereof are omitted. In this figure, the BB line is connected to the GND, and the voltage VBB is applied to the AA line via the detection resistor 21. The switches 11, 12, 13, and 14 are connected between the BB line and the B line, between the AA line and the A line, between the BB line and the A line, and between the AA line and the B line, respectively. One input terminal of the comparator 31 is A
It is connected to the A line and detects the rise of the potential V1 of the AA line.

Next, the operation of the apparatus for determining the presence or absence of disconnection of the subscriber line will be described with reference to FIGS. 1 and 2. In FIG. 1, first, the switches 13 and 14 are turned on, the switch 11 and
Turn off 12 and charge between line A and line B with voltage -VBB. Next, the switches 11 and 12 are turned on, and the switch 1
Turn off 3 and 14 and charge between line A and line B with voltage + VBB. At this time, the potential V1 of the line A instantly becomes the voltage -VBB from the voltage VBB as shown in FIG.
It changes to the voltage VBB. Further, the output voltage V2 changes from "L" to "H" at the same time when the switches 11, 12, 13, 14 are switched, and changes from "H" to "L" after a lapse of time t, that is, when V1 <Vth. . Similar to the conventional example,
The line capacitance between the A line and the B line can be known by obtaining the time t when the output voltage V2 is "H".

Next, in the above measuring method, when only the line capacitance CAB is connected to the subscriber line side, and
The waveforms of the potential V1 and the output voltage V2 when the line capacitances CAB and MJ41 are both connected are shown in FIG. In this figure, when only the line capacitance CAB is connected to the subscriber line, the potential V1 rises from the voltage -VBB to the voltage VBB at a high speed. On the other hand, when the line capacitances CAB and MJ41 are both connected to the subscriber line, the potential V1 rises rapidly from the voltage -VBB to the voltage {2 * VBB * Rmj / (Rmj + R)}-VBB, and thereafter slowly. And voltage VB
Change to B. Therefore, if the threshold voltage Vth of the comparator 31 (see FIG. 1) is set between the voltage {2 * VBB * Rmj / (Rmj + R)}-VBB and the voltage VBB, only the line capacitance CAB is connected. Rise time t1 and line capacitance CA
Since there is a difference from the rising time t2 when both B and MJ41 are connected, it is possible to determine the presence or absence of disconnection.

In addition, according to the above-mentioned subscriber line disconnection presence / absence determining device, the potential fluctuation of the potential V1 of the A line is doubled (double voltage) as compared with the conventional subscriber line disconnection presence / absence determining device. , The difference between the time t2 and the time t1 is about twice that of the conventional case.
As a result, even if the line capacitance CAB is large, it is possible to determine the presence or absence of disconnection. The line capacity CAB can be up to twice as large as the conventional determination limit capacity. Further, the setting region of the threshold voltage Vth is doubled as compared with the conventional case, and therefore the threshold voltage Vth can be set sufficiently even in consideration of the fluctuation of the voltage VBB.

[0019]

As described above, according to the present invention, it is possible to determine the presence / absence of disconnection even when the line capacitance is larger than in the conventional case. Further, the threshold voltage can be easily set even in consideration of voltage fluctuation and the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a subscriber line disconnection presence / absence determining device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining an operation of the subscriber line disconnection presence / absence determining device according to the embodiment.

FIG. 3 is a waveform diagram for explaining the operation of the disconnection presence / absence determination device for a subscriber line according to the same embodiment.

FIG. 4 is a circuit diagram showing a configuration example of a conventional device for determining the presence or absence of disconnection of a subscriber line.

FIG. 5 is a waveform diagram for explaining an operation of the disconnection presence / absence determining device for the subscriber line.

FIG. 6 is a waveform diagram for explaining the operation of the disconnection presence / absence determining device for the subscriber line.

[Explanation of symbols]

 11 to 14 switch 21 detection resistance 31 comparator 41 MJ (modular jack) CAB line capacitance Rmj resistance Cmj capacitance Vth threshold voltage VBB voltage

Front Page Continuation (71) Applicant 000005223 FUJITSU LIMITED 4-1-1 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa (71) Applicant 000000295 1-17-1 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. 72) Inventor Yoshinori Oikawa 1-6, Uchiyuki-cho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Seiichi Yamano 1-1-6, Naiko-cho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation ( 72) Inventor Toshio Hayashi 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Inventor Masahiro Imamura 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72 ) Inventor Masayuki Sakai, 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd.Hitachi, Ltd., Information & Communication Division (72) Inventor, Masafusa, 1015 Uedaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited (72) Invention Katsu Sekiguchi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Works The Corporation

Claims (4)

[Claims] 1. A disconnection presence / absence determining method for determining the presence / absence of a disconnection between first and second subscriber lines, wherein a DC voltage is applied to the first and second subscriber lines through a resistor for a predetermined time or more. Then, the DC voltage is applied between the first and second subscriber lines via a resistor with a polarity changed, and the change state of the voltage between the subscriber lines is measured. A method for determining the presence / absence of disconnection of a subscriber line, which is characterized by determining the presence / absence of disconnection based on the above. 2. The subscriber according to claim 1, wherein the measurement of the change state of the voltage between the subscriber lines is to measure the time until the voltage between the subscriber lines reaches a predetermined reference voltage. Method for determining the presence / absence of disconnection of the main line. 3. A disconnection presence / absence determining device for determining the presence / absence of a disconnection between first and second subscriber lines, a direct current power source, a resistor having one end connected to an output end of the direct current power source, and a resistor The voltage at the other end and the ground potential are respectively set to the first,
Switching means for applying to the second subscriber line and for applying the voltage and ground potential at the other end of the resistor to the second and first subscriber lines, respectively, and the voltage and the reference at the other end of the resistor. Comparing means for comparing the voltage and outputting a coincidence detection signal when the both agree with each other; and based on the output of the comparing means, the presence or absence of a disconnection between the first and second subscriber lines is determined. A device for determining the presence or absence of disconnection of a subscriber line, which is characterized by: 4. The reference voltage is the power supply voltage VBB,
When the resistance value is R and the resistance value of the modular jack connected to the first and second subscriber lines is Rmj, the voltage {2 × VBB × Rmj / (Rmj + R)}-VBB and the voltage VBB 4. The apparatus for determining the presence or absence of disconnection of a subscriber line according to claim 3, wherein the value is set to a value between and.