JPS6048693A - Central office line trunk circuit - Google Patents

Abstract

PURPOSE:To transmit an ideal dial pulse without any change in the brake rate due to a line resistance by disconnecting a capacitor of a DC shunt circuit from the circuit when a relay for forming a DC loop is turned off. CONSTITUTION:A relay K2 activated in synchronizing with a relay 3 for forming a DC loop is added. Thus, even if the relay 3 is turned off at a time T1 and a voltage is not impressed to a DC shunt circuit 4, the capacitor C2 is disconnected from a base of a transistor (TR) by the turning off of the relay K2 connected in series therewith. Thus, a voltage VC2' after charging of the capacitor C2 holds a voltage at the time T1 continuously for the time of T1, T2. When the relay 3 is turned on at the time T2 and the voltage is impressed again to the circuit 4, a collector current flows immediately to the TR. As a result, a station current IL' is an ideal discontinuous waveform having a steep leading characteristic without delay to the interruption of the relay 3 and the brake rate of the dial pulse due to the line resistor R2 is unchaged.

Description

[Detailed Description of the Invention] [Technical Envelope of the Invention] The present invention is for the station n+, u,
・It is related to the circuit.

[Background of the branch of the invention]

As is well known, (the central office line trunk circuit used in in-bank exchanges, etc.) exchanges -B"J" information between the central office and the exchange, as well as transmitting and receiving information. It has the function of creating a direct current loop f for the local current in order to perform a tail and answer.

FIG. 1 is a diagram illustrating an example of a central office line trunk circuit, which has traditionally been discouraged from use. In the figure, the J/6 line trunk circuit is connected to station 1 by two 1jlt+'6 (chip line and ring line). As shown in the figure, the DC voltage source E8 (direct αjj) of station 1 is connected to
8V DC source) and internal resistance R8, it can be done without any trouble.
Also, the direct current resistance of the line can be represented by a tag. 2 is the incoming signal from station 1 (generally 16Hz, ], O
a layered detection circuit for detecting an alternating current signal of OVrll;
3 is the response time or light (i1711i') to the incoming signal.
1 is a relay forming a DC loop, 4 is a DC loop (・C'
1, shows low resistance, and has high resistance in terms of AC fAE (low current component σ; 1° circuit) 9, DC '1Lθ1 from station 1
1 flows through this recirculation shunt circuit. 5 is a countercurrent shunt circuit that has low resistance for countercurrent and high resistance for direct current.
J/, 1tTJ', only its AC component is this AC component 01
It passes through the circuit 5 and is transmitted to the switch frame 6 in the Chichimata aircraft.

Therefore, in such a configuration, when an incoming call (number i) arrives from station 1 and the called party performs an off-footer operation in response, relay 3 closes and a DC loop is formed with station 1. At the same time, a communication path between station 9 and station 1 is formed by AC shunt circuit 5 and switch frame 6.
You can now make calls between the phone and the extension phone.

On the other hand, when a dial pulse is sent, the relay 3 is closed in conjunction with the caller's off-hook, and a DC loop is completed with the station 1. When dialing is performed in this state, the relay 3 is turned on and off the number of times corresponding to the dialed number. That is, for example, as shown in the waveform diagram of FIG. 2 on the platform where the dial number "2" is operated, the relay 3 is turned on and off twice in the intervals T1-T2 and T3-T4. As a result, a dial pulse is sent to the station 1. [Problem in the background art] By the way, the blood flow shunting circuit 4 has a transistor TR2 through which the DC current from the station 1 flows. A 1M electric appliance C2 is connected to the base, and by keeping the base potential of the transistor TR2 constant with this capacitor C2, it is possible to suppress the base's position from changing due to the AC signal superimposed on the DC current from the station 1. [・
The AC resistance between the collector and emitter of transistor TR2 is increased so that only the direct θIL component flows. However, this seedling generator C2 has the disadvantage that the dial pulse waveform is distorted by δ when sending out the dial pulse. That is, when the relay 3 is turned off at time Tl in the waveform diagram shown in FIG. 2, no voltage is applied to the DC shunt circuit 4. Therefore, the voltage vc2 after charging the capacitor (-72) passes through the path of the base of the transformer nostar TR2 → emitter → resistor R3 and is discharged with the characteristics shown in FIG. 2(b). After this, at time T2 When the relay 3 is turned on, voltage is again applied to the DC shunt circuit 4, and the capacitor C2 is charged through the resistor R2.

However, a transistor generally has a characteristic that collector current does not begin to flow unless the base-emitter voltage exceeds about 0.7V.

Therefore, the collector current of transistor TR2 does not flow at all during ΔT until charging voltage Vc2 of capacitor C2 reaches 0.7V, and even after that, since the charging voltage Vc2 rises slowly, the collector current suddenly increases. I can't stand up. As a result, the μj cage current ■1 has a waveform shape with a slow rise as shown in Fig. 2 (C), and moreover, the open current ILli
Since the standing characteristics and notes change depending on the track resistance tag,
The shortcoming was that the value of the special first order of the beans changed depending on the length of the track, and the break value of the dial pulse changed.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, to provide a central office line trunk circuit that transmits an ideal dial/zero waveform, and in which the break rate of the dial/zero does not change due to line resistance.

1', Summary of the Invention] Therefore, in the present invention, a direct current loop! The above purpose is achieved by disconnecting the capacitor of the DC shunt circuit from the circuit when the forming relay is turned off.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 3 is a diagram showing an embodiment of the present invention, and the only difference from the circuit shown in FIG. 1 is that 2 is added to a relay that operates in synchronization with relay 3 for forming a DC loop. .

Therefore, in the configuration shown in FIG. 3, at time T in FIG.
Even if relay 3 is turned off and voltage is no longer applied to DC shunt circuit 4, accumulator c2 will turn off relay 2 connected to IC in one row.
It is separated from the base. Therefore, the 71 voltage Vc2' after charging of #electrical appliance C2 continues from time T1 to time T2 and maintains the voltage at time T1, as shown in FIG. 2(f). Therefore, when the relay 3 is turned on at time T2 and voltage is applied to the DC shunt circuit 4 again, the transistor T
A collector current immediately flows through R2.

As a result, the return current ■L has an ideal intermittent waveform with a steep rising characteristic with no delay with respect to the intermittent connection of the relay 3, as shown in Figure 2 (f), and is dialed in depending on the line resistance. The pulse break rate also no longer changes.

〔Effect of the invention〕

As explained above, the present invention is designed to disconnect the DC shunt circuit from the circuit when the relay for forming the DC loop is turned off due to the generation of dial noise. This has the advantage that the break rate does not change due to resistance, and dial pulses with an extremely ideal waveform can be sent out.

[Brief explanation of drawings]

FIG. 1 shows an example of a conventional open door trunk circuit, FIG. 2 is a waveform diagram of each part of a conventional central office line trunk circuit and a central office line trunk circuit according to the present invention, and FIG. 3 is a diagram according to the present invention. It is a figure showing one example of a central office line trunk circuit. 1... Station, 2... Incoming call detection circuit, 3... Relay for DC loop formation, 4... DC branch C4 circuit, 5.
Father v11 shunt circuit, 6... switch frame.

Claims (1)

[Claims] In a central office line trunk circuit comprising a first circuit that passes only the alternating current component of the voice signal in the subscriber line and a second circuit that passes only the direct current component, the direct current path of the second circuit is configured. Connected to the base of the transistor h'
It is characterized in that it is provided with a switching means for disconnecting the capacitor from the dial pulse from the base of the transistor when the dial pulse occurs. circuit.