JP2000050321A - Fault detection circuit for two-wire subscriber circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fault detection circuit that surely transmits SCN information to an exchange control system in the case of a fault contact of AC power supply and a subscriber line. SOLUTION: In the 2-wire subscriber circuit that transmits a fault state such as an AC contact with a subscriber line or the like superimposed on an SCN signal to an exchange control system, an over-voltage detection circuit 4 that outputs over-voltage information S4 when being applied with the voltage higher than an each level of a feed circuit 2 is provided on the side of a subscriber line L1, an over-voltage detection circuit 3 that outputs over-voltage detection information S3 when being applied with the voltage lower than a feeding circuit power supply voltage L1 is provided on the side of a subscriber line L2, and an over-voltage information storage circuit 6 that stores the sum information of the respective over-voltage detection information for a prescribed time is provided. Then the output of the storage circuit 6 is superimposed on the SCN signal and the resulting signal is sent to an exchange.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal voltage detecting circuit for detecting that an abnormal voltage is applied to the subscriber line side of a two-wire subscriber circuit, and more particularly to an exchange for detecting information on overvoltage caused by a contact of a commercial power supply. To a failure detection circuit that protects each part of the subscriber's circuit by transmitting the information to the failure detection circuit.

[0002]

2. Description of the Related Art Conventionally, in a two-wire subscriber circuit accommodated in a subscriber exchange, when a line abnormal voltage fault such as a contact with an AC power source in a subscriber's house and a subscriber line is detected, the subscriber line is used. The loop current information flowing through the feeder circuit of the subscriber circuit due to the application of the abnormal voltage to the
A signal is created and an abnormal state is transmitted to the control system of the exchange as SCN information.

A known example related to the detection of a line failure in such a two-wire subscriber circuit is disclosed in Japanese Patent Laid-Open No. 7-2311.
No. 0 and Japanese Unexamined Patent Application Publication No. 10-0556510 and the like.

[0004]

A power supply circuit of a subscriber circuit is generally composed of a power transistor or the like and can supply a power supply current only in a fixed direction. In the case of a line fault detection circuit configured to detect a voltage-applied fault based on loop current information flowing through the subscriber's circuit and transmit the information as SCN information to the control system of the exchange, the fault such as AC power supply cross fault or the like is added. If an abnormal voltage exceeding the power supply voltage range of the power supply circuit is applied to the subscriber line, the supply current does not flow due to the direction of the transistor, and there is a time when the SCN information is not generated. There is a problem that the voltage application state cannot be transmitted accurately.

An object of the present invention is to generate SCN information even when an abnormal voltage exceeding a power supply voltage range for a subscriber circuit is applied to a subscriber line. To provide a failure detection circuit for transmitting SCN information to an exchange control system.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a two-wire subscriber circuit which superimposes an abnormal state such as AC touch on a subscriber line on an SCN signal and transmits it to a switching control system. In the fault detection circuit of (1), L1 side overvoltage detection means for outputting overvoltage information when a voltage higher than the earth potential of the feeder circuit of the subscriber circuit provided on the L1 side of the two-wire subscriber line is applied; L2 side overvoltage detection means for outputting overvoltage detection information when a voltage lower than the power supply circuit power supply voltage provided on the L2 side of the two-wire subscriber line is applied, and sum information of these two overvoltage detection information Since the sum information output means for outputting and the sum information of the overvoltage detection information are superimposed on the SCN signal and transmitted to the exchange, when an abnormal voltage exceeding the power supply voltage range of the subscriber circuit is applied to the subscriber line, Also generates an SCN signal Can live.

Further, according to the present invention, an overvoltage information holding circuit for holding the overvoltage detection information for a certain period of time is provided, and the output of the overvoltage information holding circuit is superimposed on the SCN signal and transmitted to the exchange control system. The abnormal voltage periodically changes from 0V to 120V as in the case of AC power supply of the subscriber line.
Even in the case where the SCN signal fluctuates within the range, it is possible to provide a failure detection circuit of a two-wire subscriber circuit that can reliably transmit the SCN information to the switching control system without fluttering of the SCN signal.

Further, when only one of the subscriber lines L1 and L2 is in contact with the AC power supply, the overvoltage information can be detected only in one of the positive cycle and the negative cycle of the AC power supply. The overvoltage detection information can be held until the next cycle of the AC power supply by setting the holding time of
Provided is a failure detection circuit for a two-wire subscriber circuit that can reliably transmit SCN information to an exchange control system without fluttering of SCN signals even when only one or both of the subscriber lines L1 and L2 are in contact with AC power. it can.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a fault detecting circuit for a two-wire subscriber circuit according to the present invention. FIG. 1 shows a basic configuration diagram of a fault detection circuit for a two-wire subscriber circuit according to the present invention. The fault detection circuit of the two-wire subscriber circuit according to the present invention includes a power supply circuit 1 including a PNP transistor for power supply on the L2 (A line) side, and a power supply N on the L1 (B line) side.
A power supply circuit 2 including a PN type transistor and an A line (L2)
Input voltage on the A side (L2) side power supply voltage 1 of the power supply circuit 1 side
A-line (L2) side overvoltage detection circuit 3 that outputs overvoltage information when the voltage becomes lower than BB (for example, -48V)
B line (L1) that outputs overvoltage information when the input voltage on the B line (L1) side is higher than the ground potential.
Side overvoltage detection circuit 4, a loop detection circuit 9 for detecting a call from a telephone through loop current information from the A line side power supply circuit 1 and the B line side power supply circuit 2, and control from the exchange side. A control circuit 7 for operating the thyristor switch 8 in response to the signal S8, a thyristor switch 8 for turning on / off the connection between the subscriber circuit and the subscriber line when a control signal S7 from the control circuit 7 is received, An OR circuit 5 serving as sum information output means for outputting sum information S5 of the overvoltage detection information S3 of the line (L2) side overvoltage detection circuit 3 and the overvoltage detection information S4 of the B line (L1) side overvoltage detection circuit 4; Circuit 5
And an OR circuit 10 for outputting sum information S6 of the output S9 of the loop detection circuit 9 and the output of the overvoltage information holding circuit 6, and an SCN signal generating circuit 11. Is done.

The A line (L2) side overvoltage detection circuit 3 receives the overvoltage detection information S3, the B line (L1) side overvoltage detection circuit 4 receives the overvoltage detection information S4, and the OR circuit 5 outputs the B line (L1) and A
The control circuit 7 uses the information sum S5 of the overvoltage detection information from the line (L2) and the control signal S7 for controlling the thyristor switch 8 for turning on / off the connection between the subscriber circuit and the subscriber line.
The OR circuit 10 calculates the sum information S10 of the held information S6 from the holding circuit 6 and the loop signal S9 from the loop detection circuit 9.
Is output.

First, the outline of the operation of the AC cross-contact protection of the fault detection circuit shown in FIG. 1 will be described. When the overvoltage S2 due to AC cross-contact with the B line (L1) is cross-contacted, if the cross-contact voltage from the B line (L1) becomes higher than the G earth of the power supply NPN transistor of the power supply circuit 2, the overvoltage detection circuit 3 will operate. The overvoltage detection information S4 is transmitted to the information holding circuit 6. When an overvoltage due to AC cross-contact causes cross-contact to the A-line (L2), the cross-contact voltage S1 from the A-line (L2) changes to the power supply PN of the power supply circuit 1.
When the voltage is lower than the power supply voltage of the P-type transistor,
The A-line side overvoltage detection circuit 3 transmits the overvoltage detection information S3 to the overvoltage information holding circuit 6.

The sum information S10 of the sum information S5 of each overvoltage detection information and the loop signal S9 from the loop detection circuit 9 is SC
When transmitted to the exchange by the N signal, a control signal S8 is transmitted from the exchange to the control circuit 7.

Normally, upon detecting the SCN signal, the exchange control system recognizes the subscriber's off-hook condition and shifts to waiting for dial reception. However, when an SCN signal due to a failure is received, the dial information is not received even if the operation shifts to a dial waiting state, so that the dialing information is recognized as abnormal, and the subscriber circuit is controlled to a high and dry state by the control signal S8 to control the thyristor. By operating the thyristor switch 8 to be turned off by the signal S7, it is possible to cut off the line side so that the abnormal AC voltage is not continuously applied to the subscriber circuit.

Next, the operation of this fault detection circuit will be described with reference to the operation waveforms of FIG. 2, taking an example in which an AC touch fault occurs only on the B line (L1) side in FIG. FIG. 2 shows operation waveforms of each part of the fault detection circuit according to the present invention. In FIG. 2, a period from t1 to t2 indicates a contact failure occurrence period. Before and after that, there is no touch. In FIG. 2, S1 is the waveform of the overvoltage caused by AC touching of the A line (L2), S2 is the waveform of the overvoltage caused by AC touching of the B line (L1), and S3 is the detection of the A line side overvoltage detected by the A line side overvoltage detection circuit 3. Information waveform,
S4 is an overvoltage detection information waveform detected by the B line side overvoltage detection circuit 4, S5 is a sum information waveform of the A line side overvoltage detection information S3 and B line side overvoltage detection information S4, and S6 is an output waveform of the overvoltage information holding circuit 6. is there. The A line side overvoltage detection information S3 is
The A-line side overvoltage detection circuit 3 detects the AC touch from the A line (L2), and is output in the negative polarity portion of the AC touch waveform S1 that is lower than the power supply voltage VBB. The B line side overvoltage detection information S4 is information obtained by detecting the AC touch from the B line (L1) by the B line side overvoltage detection circuit 4, and is output in the positive polarity portion of the AC touch waveform S2 higher than the G ground potential. . The overvoltage information holding signal S6 is output as a continuous waveform by holding the overvoltage detection information in the overvoltage information holding circuit 6 for a certain period of time.

When only the B line (L1) side has an AC touch, the output S4 of the B line (L1) side overvoltage detection circuit 4
If only the SCN signal is sent to the SCN signal transmission circuit 11, the period during which no SCN signal is generated increases, and during the period when no SCN signal is generated, the overvoltage S2 due to AC contact is applied to the power supply circuit 2. Therefore, as shown in FIG. 1, the holding circuit 6 for holding the overvoltage detection
Provided before the N signal transmission circuit 11. As a result, as shown in FIG. 2, the output signal S6 of the overvoltage information holding circuit 6 can make the time during which the SCN signal is output longer than the overvoltage information S4 on the B line (L1) side. Even in the case of single-line AC cross contact in which an overvoltage is applied only to the side ()), the overvoltage can be prevented from being applied to the power supply circuit for a long time.

Further, the sum information S5 sent to the SCN signal generation circuit 11 is output to the SCN signal generation circuit 11 even in the case of single-line contact due to the circuit configuration of the overvoltage information holding circuit 6, for example, until the next SCN signal comes in the capacitor discharge circuit. , The overvoltage can be prevented from being applied to the power supply circuit at all.

[0017]

As described above, according to the two-line subscriber line fault detecting circuit of the present invention, the B line (L1) and the A line (L
Since there is means for superimposing the sum information of the overvoltage detection circuit provided in each of the above 2) on the SCN signal and transmitting it to the exchange, an abnormal voltage exceeding the power supply voltage range of the subscriber circuit is applied to the subscriber line. Also in this case, SCN information can be generated and transmitted to the exchange control system.

Further, a holding circuit for holding the overvoltage detection information for a predetermined time is provided, and the output of the holding circuit is superimposed on the SCN signal and transmitted to the exchange control system. Can be reliably transmitted to the exchange control system without causing the SCN signal to fluctuate.

Further, even when only one of the subscriber lines B (L1) and A (L2) is in contact with the AC power supply, the holding time of the circuit for holding the overvoltage information is set to a half cycle or more of the AC power supply frequency. As a result, the overvoltage detection information can be held until the next cycle of the AC power supply, so that the SCN information can be reliably transmitted to the switching system without fluttering of the SCN signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a fault detection circuit according to the present invention.

FIG. 2 is an operation waveform of each unit of the fault detection circuit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A-line side power supply circuit part 2 B-line side power supply circuit part 3 A-line side overvoltage detection circuit 4 B-line side overvoltage detection circuit 5 OR circuit 6 Overvoltage information holding circuit 7 Control circuit 8 Thyristor circuit holding circuit 9 Loop detection circuit 10 OR circuit 11 SCN signal generation circuit

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shinya Ota 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Information and Communication Division, Hitachi, Ltd. 5K019 AA08 AC04 BA52 BB34 BB36 CC02 CD02 5K037 AA07 AD02 CB09

Claims (3)

[Claims] 1. A fault detecting circuit for a two-wire subscriber circuit, which superimposes an abnormal condition such as AC touch on a subscriber line on an SCN signal and transmits the superimposed signal to an exchange control system, on the L1 side of the two-wire subscriber line. L1 side overvoltage detecting means for outputting overvoltage information when a voltage higher than the earth potential of the power supply circuit of the provided subscriber circuit is provided, and a power supply circuit power supply provided on the L2 side of the two-wire subscriber line L2 side overvoltage detection means for outputting overvoltage detection information when a voltage lower than the voltage is applied; sum information output means for outputting sum information of these two overvoltage detection information; A fault detecting circuit for a two-wire subscriber circuit, which is superimposed on a signal and transmitted to an exchange. 2. The fault detecting circuit for a two-wire subscriber circuit according to claim 1, further comprising an overvoltage information holding circuit for holding the overvoltage detection information for a predetermined time, and superimposing an output of the overvoltage information holding circuit on an SCN signal. A fault detecting circuit for a two-wire subscriber circuit, wherein the fault is transmitted to a switching system. 3. A fault detecting circuit for a two-wire subscriber circuit, wherein a holding time of the overvoltage information holding circuit according to claim 2 is at least a half cycle of an AC power supply frequency.