JPS63146594A - Electronic choke circuit - Google Patents

Abstract

PURPOSE:To attain the reception without dial pulse distortion sent from a loop circuit by providing a means short-circuiting a resistor of a capacitor charging circuit to bring a transistor (TR) of the electronic choke circuit from the cut-off state into the saturation state. CONSTITUTION:In receiving a pulse from an opposite station, a short-circuit 12 is operated at a predetermined time before the reception to short-circuit the resistor. Thus, the capacitive element 6 at loop open/close (dial pulse reception) state is charged with a very small time constant. Thus, the TR 10 goes to the saturating region from the cut-off region at a high speed, then no delay is caused at the leading of the dial pulse (causing distortion).

Description

[Detailed Description of the Invention] () Already Required A means for short-circuiting a resistor of a capacitor charging circuit for causing a transistor of an electronic choke circuit to transition from a cut-off state to a saturated state is provided.

[Industrial application field]

The present invention relates to an electronic choke circuit, and more particularly, to an electronic choke circuit that has high responsiveness to pulses (dial pulses) used in telephone communications and the like.

In a telephone switching system, DC power is supplied from the exchange center to its subscriber terminals for sending out dial pulses, etc., and the same DC power is supplied between stations from the own station (receiving station) to the opposite station (originating station). It is done. These DC power supplies are carried out via lines through which speech signals are transmitted. Therefore, the above-mentioned DC power supply is performed via a choke coil and a line. .

However, the bulkiness of the choke coil becomes more noticeable as the number of lines increases. Therefore, electronic choke circuits have come to be used to reduce the size of the choke circuits. Although this circuit certainly satisfies the purpose of miniaturization, the choke coil lacks any choke characteristics, especially its responsiveness to dial pulses, so improvements are required.

[Conventional technology]

FIG. 4 shows a circuit diagram for direct current power supply between stations. In this figure, 100 is a dial pulse sending circuit of the opposing station 102. When sending out dial pulses from the dial pulse sending circuit 100, the dial pulse sending circuit 10
The following DC power supply loop is formed from the local station 104 to the station 104. The loop is ground G, and the local DC loop resistance is 1.
06, electronic choke circuit 10B, loop detection circuit 11
0, line resistance 112, dial pulse sending circuit 100,
This is a DC power supply loop that connects to a 148 volt power source via a line resistance 114, an electronic choke circuit 116, and an in-station DC loop resistance 118.

When this loop is formed, a pulse current flows through the loop by opening and closing the relay switch 100 of the dial pulse sending circuit 100 ((a) in FIG. 5). It is sent to the own station 104. The dial pulse is detected by a known loop detection circuit 110, and the pulse train 5C
N ((b) in FIG. 5) is used to detect the pulse width of a scanning pulse for extracting a dial number, etc. Note that the call signal from the line is taken into the exchange via lines 109 and 115.

[Problem that the invention seeks to solve]

The dial pulses flow through electronic choke circuits 108, 116 as described above.

However, since these electronic choke circuits have a capacitor 6, the electronic choke circuits 108, 1 are not charged until the charging of the capacitor 6 reaches a predetermined value for moving the NPN transistor 10 into the saturation region.
16 exhibits low impedance. The time required to reach the above value is determined by the product of the capacitance C of the capacitor 6 and the resistance value R of the resistor 8, that is, the time constant RC. Because of this time constant, the rise of each pulse of the dial pulse train detected by the loop detection circuit 110 (pulse train SC
Rising edge of each dial pulse of N) is relay switch 1
From the closing side of 001 ((a) in FIG. 5), the time constant RC
((b) in FIG. 5). Therefore, the pulse width of each pulse in the dial pulse train becomes narrow. Therefore, the narrower the original pulse, the higher the width narrowing rate, and in extreme cases, it may become impossible to detect a pulse with a high width narrowing rate by the aforementioned scanning pulse. This means that the dialed number cannot be correctly transmitted to the exchange, and the situation is serious.

Note that the resistor 16 of the electronic choke circuit is for determining VCE and VBE of the transistor 10 to appropriate values as shown in FIG. 6, and the resistor 18 is for temperature compensation of the transistor 10.

The present invention was created in view of such problems, and an object of the present invention is to provide an electronic choke circuit that does not distort pulses applied at predetermined times in an operating time series.

[Means for solving problems]

FIG. 1 shows a block diagram of the principle of the present invention. In this figure, 2.4 is a choke terminal of the electronic choke circuit, and 6.8 is a capacitive element and a resistor connected in series between the choke terminals 2 and 4, respectively.

16 is a resistor connected in parallel between the terminals of the element 6 and the resistor 8 connected in series. A transistor 10 driven by the potential at the node between the element 6 and the resistor 8 is connected between the terminals 2.4. The electronic choke circuit of the present invention is characterized by providing the shorting means 12 between the terminals of the resistor 8 of the electronic choke circuit constructed in this manner.

[For production]

When the circuit of the present invention is installed in the opposite station line of an exchange to receive a dial pulse from the opposite station, the shorting means 12 is operated at a predetermined time before receiving the dial pulse to short-circuit the resistor.

Thereby, the capacitive element 6 is charged with an extremely small time constant during loop opening/closing (dial pulse reception). Therefore, the transistor 10 moves from its cut-off region to its saturation region at high speed, so that it can receive the dial pulse without causing any delay (or distortion) in the rise of the dial pulse as described above.

〔Example〕

FIG. 2 shows an embodiment of the present invention, which is used in place of the electronic choke circuit of FIG. 4 described above.

This figure is the same as the circuit in Figure 4, except for the photocoupler energization system that connects the power supply VCC, which constitutes the so-called short-circuiting means 12 in Figure 1, to the resistor 20, the photocoupler 22, and the relay driver 24, so these circuits have the same configuration. Elements will be given the same reference numerals and their descriptions will be omitted. The collector and emitter of the phototransistor 222 of the photocoupler 22 are connected between the terminals of the resistor 8 so that the resistor 8 can be short-circuited. The relay driver 24 may also be used as a relay driver that returns a reverse response to the game.

The operation of the circuit of the present invention constructed in this manner is illustrated in FIGS. 2 and 3.
This will be explained with reference to the figures and FIG. However, it is assumed that the relay driver 24 is also used as a reverse relay driver.

When a dial pulse is sent from the opposing station, a loop is formed with the opposing station via the line 113, and when a current flows through the loop (see the θ part in FIG. 3 (al)), a signal from the loop detection circuit 110 is generated. The control unit (not shown) of the own station (receiving station) that responds to this sends a reverse response pulse (dial pulse reception ready signal) RB (Fig. 3) to the reverse relay driver 24 in order to return a reverse response to the opposing station.
b))) and returns a reverse response to the player. Reverse relay driver 2 due to reverse signal at low level
The output of 4 becomes "0", and the photocoupler 22 is energized before the reverse response is returned, but the output of the driver 24 becomes "1" due to the reverse response pulse, and the energization is temporarily canceled during the pulse width of that pulse. However, since direct current is already being applied to the capacitor, there is no effect on the operation of the electronic choke circuit.

After the player responds to the above-mentioned reverse response, the relay switch 100+ of the player opens and closes, as shown in FIG. 3 (a).
A dial pulse as shown in part B of ) is sent out.

At this time, the photocoupler 22 is energized and the resistor 8 is short-circuited, so that the capacitor 6 is charged extremely quickly. Therefore, transistor 10 quickly switches from the cutoff region to the saturation region. In other words, the leading edge of each dial pulse has a steep rise, and the dial pulse can be received accurately.

During a call after receiving the dial pulse in this manner, the signal RB changes to a high level, so the output of the relay driver 24 becomes "1" and the photocoupler 22 is turned off. Therefore, the electronic choke circuit exhibits low impedance to DC components and high impedance to AC bones, as in the conventional case.

Note that the transistor 10 may be of a PNP type. It is necessary to change each element accordingly. Further, the photocoupler 22 may be replaced with another switch.

〔Effect of the invention〕

As explained above, according to the present invention, responsiveness to applied pulses (trains) is improved. For example, when the present invention is applied to a DC loop circuit of a loop dial line trunk, it is possible to receive dial pulses sent through the loop circuit without distortion.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the present invention; Fig. 2 is a diagram showing an embodiment of the present invention; Fig. 3 is a time chart; Fig. 4 is a diagram showing an example of use of a conventional electronic choke circuit; This figure is an illustrative diagram of the response of the circuit shown in FIG. 4, and FIG. 6 is a diagram for explaining the role of the resistor 16 in the circuit shown in FIG. 1 and 2, 6 is a capacitive element 51, (capacitor), 8.16, 18
．． 20 is a resistor, 10 is a transistor, and 12 is a short circuit means (resistance 20, photocoupler 22, relay driver 24). Patent applicant: Fujitsu Ltd. 4 (Blue Moon Delta Madness) Lock Diagram Figure 1 No. Enmei no Emugihiko 11 Figure 2 Time Timer Figure 3 1c. ``Tips'' U Kaikuni lj'r3-ri circuit-, (Historical example 4th figure 4) Illustrated diagram 5) Transistor log\, /CE, BE○S How to put on E
Congratulatory party No. 6

Claims (1)

[Claims] A capacitive element (6) and a resistor (8) connected in series between the choke terminals (2, 4), and a resistor (16) connected in parallel between the terminals of the series connected element (6) and resistor (8). and a transistor (10) interposed between the choke terminals (2, 4) and driven by a predetermined potential, the shorting means (1) shorting the resistor (8).
2) An electronic choke circuit characterized by providing the following.