JPH0683493B2 - DC loop control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In the case of sending a dial signal by intermittently connecting a DC loop circuit of a trunk using an electronic choke circuit having a time constant in which a resistor and a capacitor are connected in series between both ends. In order to eliminate the waveform distortion of the current flowing through the subsequent DC loop circuit, the resistance and the capacitor of the computerized choke circuit are connected by the on / off circuit before the dial signal is sent by the intermittent contact of the relay of the DC loop circuit. The connection is turned off to set the time constant to 0 to eliminate the occurrence of distortion due to the time constant, and after turning on the dial signal, it is turned on to connect the capacitor in which the electric charge is originally stored to eliminate the distortion due to the charging of the capacitor.

[Industrial application field]

The present invention relates to an improvement in a DC loop control system of a DC loop circuit of an analog trunk of a digital exchange, which uses an electronic choke circuit having a time constant in which a resistor and a capacitor are connected in series between both ends.

In the above DC loop control method, it is desirable to eliminate the waveform distortion of the current flowing through the DC loop circuit when the dial signal is sent to the opposite trunk by intermittently connecting the DC loop circuit and to eliminate the malfunction.

[Conventional technology]

 A conventional example will be described below with reference to the drawings.

FIG. 3 is a circuit diagram mainly showing a DC loop circuit in the case of an outgoing trunk of a conventional example, and FIG. 4 is a time chart of a current waveform of the DC loop circuit.

The electronic choke circuit 1 will be described. The resistors 2, 7 and 8 supply a DC bias to the transistor 6, and the capacitor 3 prevents an AC bias from being applied between the base and emitter of the transistor 6. It is for AC bypass.

When the collector side of the transistor 6 is set to a high potential and a DC power supply with an AC signal superimposed is connected between both ends, the transistor 6 is a capacitor 3 so that the base and the emitter are DC biased and the voltage fluctuates. Therefore, the direct current flows through the path of transistor 6 and resistor 8,
The alternating current cannot pass through this path, that is, it is a choke circuit.

The alternating current flows through the path of the resistor 2 having a large resistance value and the capacitor 3, and the alternating current impedance is substantially equal to the resistance 2 having a large resistance value.

Next, the outgoing call operation of the outgoing trunk using the electronic choke circuit 1 will be described.

When an OG relay (not shown) is activated for transmission, the trunk 30 of the opposite exchange has a ground-line 19-A relay contact 4-electronic choke circuit 1-OG relay contact 9
-Line 20-Starting the opposite exchange by forming a DC loop of -48V in the trunk 30 of the opposite exchange, further activating the A relay (not shown) to send the dial pulse, and disconnecting the contact 4. The dial pulse is sent to the opposite exchange by interrupting the current flowing through the DC loop.

However, since the electronic choke circuit 1 has a time constant consisting of the resistor 2 and the capacitor 3, when the contact 4 is closed, the actual flow of the current in the DC loop is delayed, and FIG.
When the contact 4 is interrupted as shown in FIG. 3, a distorted waveform is obtained as shown in FIG. This may cause a malfunction in detecting the dial pulse.
A circuit consisting of a contact 18 of a CT relay (not shown) is provided in series, and the CT relay is operated only when sending a dial pulse train to turn on the contact 18, and the earth of the trunk 30 of the opposite exchange-the line 19-A relay Contact 4-Resistance 17-CT relay contact 18-Line 20-Trunk 30 trunk of the opposite exchange-Close the DC loop of -48V so that the time constant of the electronic choke circuit 1 does not affect the transmission of dial pulse. There is. As a result, the waveform of the current in the DC loop becomes as shown in FIG.

[Problems to be solved by the invention]

However, if the CT relay is restored and the contact 18 is turned off after sending the dial pulse train, the DC current flows into the capacitor 3 again with the above time constant, so that the DC loop breaks as shown in FIG. 4 (C). The situation becomes similar, and there is a problem that the TRAQ on the receiving side may mistake this as a dial pulse.

[Means for solving problems]

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

In the figure, as shown in FIG. 1, 1 is a transistor 6 and a resistor 8 connected in series between one terminal and the other terminal, and a resistor 2 is connected between the transistor 6 and a collector / base. Further, between the base of the transistor 6 and the other terminal, a parallel circuit of a resistor 7 and a capacitor 3 is connected, one terminal of which is the contact 4 of the A relay and the other of which is the other terminal. In a DC loop circuit of an analog trunk of a digital exchange, a terminal of which is connected to a contact 9 of an OG relay, a connection between the base of the transistor 6 and the capacitor 3 and a connection between the base of the transistor 6 and the capacitor 3 are turned on / off. An on / off circuit 5 is provided. Then, the connection between the base of the transistor 6 and the capacitor 3 is turned off by the on / off circuit 5 before sending the dial pulse train when the contact 4 of the A relay is intermittent, and turned on after sending the dial pulse train. To do.

A DC loop circuit of an analog trunk in a digital exchange is constructed by the above components as shown in FIG.

[Action]

In the present invention, the resistor 2 and the capacitor 3 having the time constant of the electronic choke circuit 1 are provided immediately before the dial pulse train is transmitted by intermittently connecting the DC loop circuit to the contact 4 of the A position relay.
The connection with and is turned off by the on / off circuit 5, and the time constant is set to zero. As a result, the distortion due to the time constant of the dial pulse disappears, and after the dial pulse train is transmitted, the on / off circuit 5
Since the capacitor 3 in which the electric charge is accumulated is connected again immediately before sending the dial pulse train, the distortion due to the charging of the capacitor is also eliminated.

Therefore, there is almost no waveform distortion of the current flowing through the DC loop circuit when transmitting the dial pulse and after the transmission of the dial pulse, and it is possible to realize a DC control system that does not malfunction.

[Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a circuit diagram mainly showing a DC loop circuit in the case of the bidirectional trunk according to the embodiment of the present invention.

In the figure, 13 and 14 are choke circuits for preventing voice signals from flowing into the power supply side of the local station when an incoming call is made, and are composed of choke coils or electronic choke circuits. 15, 16 are current limiting resistors, 10 is a rectifying circuit for keeping the current direction of the electronic choke circuit 1 constant even when the power source of the game has reverse characteristics, and 12 limits the current flowing in the DC loop. Electronic choke circuit
1, a DC loop current detection circuit 11, a current limiting circuit for protecting the rectifier circuit 10, 11 is a DC loop current detection circuit for detecting the current flowing in the DC loop.

When the OG relay (not shown) is operated to make a call, and the contact 9 is set to the dotted line side, the trunk 30 of the opposite exchange, the ground line 19-the contact point of the A relay 4-the DC loop current detection circuit 11-the rectification circuit 10-Electronic choke circuit 1-Rectifier circuit 10
-Current limiting circuit 12-Contacts of OG relay 9-Line 20-Trunk 30 of opposite exchange A DC loop of -48V is formed to start the opposite exchange.

Immediately before sending the dial pulse train, the on / off circuit 5 is turned off, the A relay (not shown) is operated to open / close the contact 4, and the direct current loop current is opened / closed to send the dial pulse to the opposite station. . At this time, since the time constant of the electronic choke circuit 1 is 0, the waveform distortion of the dial pulse does not appear.

After the dial pulse train is transmitted, the on / off circuit 5 is turned on, whereby the electronic choke circuit 1 functions as the original choke again, but at this time, the capacitor 3 has the electric charge accumulated immediately before the dial pulse train is transmitted. Therefore, unlike the conventional case, the charging current does not flow, and the current flowing in the DC loop circuit becomes free of distortion as shown in FIG. 4 (D), and malfunction does not occur.

When receiving an incoming call, the trunk 30 of the opposite exchange forms a DC loop, and the earth of the station-the resistor 15-the choke circuit 13-the DC loop current detection circuit 11-the contact point 4 of the A relay 4-the line 19-the DC loop of the opposite station-the line 20-CG relay contact 9-Choke circuit 14-Resistor 16-Current flows through -48V route of own station,
By detecting the current in the DC loop current detection circuit 11, it is found that the trunk of the own station has been called and it is activated.

It should be noted that the electronic choke circuit is not shown, but it is clear that the present invention is symmetrical to the present invention as long as it has a time constant in which a resistor and a capacitor are connected in series between both ends.

〔The invention's effect〕

As described in detail above, according to the present invention, the waveform distortion in the case of transmitting the dial signal by intermittently connecting the DC loop circuit and the state similar to the state of the disconnection of the DC loop after the transmission are eliminated, so that the malfunction occurs. It has the effect of disappearing.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the principle of the present invention, FIG. 2 is a circuit diagram mainly showing a DC loop circuit in the case of a bidirectional trunk according to an embodiment of the present invention, and FIG. 3 is a DC loop in the case of a conventional outgoing trunk. FIG. 4 is a circuit diagram mainly composed of a circuit, and FIG. 4 is a time chart of current waveforms of a DC loop circuit. In the figure, 1 is an electronic choke circuit, 2, 7, 8, 15 to 17 are resistors, 3 is a capacitor, 4 is an A relay contact, 5 is an on / off circuit, 6 is a transistor, 9 is an OG relay contact, 10 Is a rectifier circuit, 11 is a DC loop current detection circuit, 12 is a current limiting circuit, 13 and 14 are choke circuits, 18 is a CT relay contact, 19 and 20 are lines, and 30 is a trunk of an opposite exchange.

Claims (1)

[Claims] 1. A transistor (6) and a first resistor (8) are connected in series between one terminal and the other terminal, and a second resistor is provided between the collector and base of the transistor (6). (2) is connected, and between the base of the transistor (6) and the other terminal, a parallel circuit of a third resistor (7) and a capacitor (3) is connected. ), The transistor (6) in the analog trunk DC loop circuit of the digital exchange, the one terminal of which is connected to the contact (4) of the A relay and the other terminal of which is connected to the contact (9) of the OG relay. An on / off circuit (5) for turning on / off the connection between the base of the transistor (6) and the capacitor (3) is provided between the base of the transistor (6) and the capacitor (3). ) Connection A DC loop control system characterized in that an on / off circuit (5) is turned off before sending a dial pulse train when the contact (4) of the A relay is intermittent and turned on after sending the dial pulse train.