JPS5940755A - Charging signal transmitting circuit - Google Patents

Abstract

PURPOSE:To attain miniaturization and light weight and to reduce noise generated at the transmission of charging signal, by operating a switching transistor (TR) just before the leading edge and trailing edge of a polarity inverting pulse so as to decrease the level of a signal current. CONSTITUTION:A low pass filter is arranged between a contact of a polarity inverting relay and a channel, and switching TR is arranged between the polarity inverting relay and a power supply respectively and the switching TR is operated just before the pulse leading and trailing of the said polarity inversion. In inverting the polarity of the channel, since no current flows to the channel, no noise is generated. Then, the 2nd pulse is applied to a filter F and the collector current of a TR1 is decreased gradually. The line current is inverted through the polarity inversion in this case and an MP relay is restored while the current of the channel is zero. The noise is reduced remarkably by controlling the waveform of the current in this way, but a slightly rapid changing point remains in the waveform, which might cause a noise, then the waveform is smoothed further with an LPF.

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a billing signal sending circuit.
This invention relates to a polarity inversion pulse sending method that can reduce the size and weight of the filter L by using a current control circuit using switching transistors.

(1)) Prior art and problems Figure 1 shows an example of a conventional billing signal sending circuit. In Figure 1, OGT is the transmitting side exchange, lines a and b are communication lines, and A is for OGT monitoring. Relay, El is power supply, IJPF'
is a low-pass filter, and coil L1/Dente C
1, (! Consists of 2.03, both r and mp are the contacts of the relay RL and the polarity reversal relay MP. 04 is the capacitor, and HYB is the transformer.

Figure 2 shows the voltage and current waveforms at each part in Figure 1.
(a) Figure shows the operation of relay MP, (b) Figure 1 shows the voltage waveform at point 0 in Figure 1, Figure (C) shows the current waveform at point 0 in Figure 1, and (d
) Figure 1 shows the current waveform at point ■ in Figure 1. Below, a conventional charge signal sending circuit will be explained with reference to Figure 1. In conventional billing signal sending circuits, noise is generated when sending billing signals. In other words, relay RL receives a response signal from the receiving side,
When entering the call state, contact R! maintains an operating state (shown by a dotted line), and during a call, the a line is on the power supply El side and the b line is on the ground side. Charging signal (pulse signal in Figure 2 (a),
When a wire (width 200m5) comes in, the MP relay operates, and the polarity is reversed for about 200 ms (line a: ground side, line b:
On the battery side), when the pulse signal shown in FIG. 2(a) ends, the polarity is restored. At this time, the polarity is reversed and restored through the Ronox filter circuit LPF"i. This is the function of the billing signal sending circuit. However, the transient current due to charging and discharging of the DC cut capacitor 04 of the HYB transformer (( d) Figure) flows and generates noise. This is due to the saturation of the HYB) lance due to transient current.L, which is a component of a low-pass filter to remove this noise, supplies direct current to the telephone line. In addition, in order to operate effectively as the L of a low-pass filter, it becomes large and expensive.For this reason, the billing signal sending circuit becomes large, and high-density packaging is impossible, making it expensive. There is.

(Q) Object of the Invention An object of the present invention is to eliminate the above-mentioned drawbacks and provide a billing signal sending circuit that is smaller and lighter than conventional devices.

(d) Structure of the Invention According to the present invention, in a method of relaying polarity reversal and pulses sent from a receiving exchange to a transmitting exchange, the present invention provides a method for relaying polarity reversal relays and communication lines between the contacts of a polarity reversal relay and a communication line. A low-pass filter is placed between the polarity reversing relay and the power supply, and a switching transistor is placed between the polarity reversing relay and the power supply, and the switching transistors are operated just before the rising and falling edges of the polarity reversing pulse, thereby reducing the signal flowing through the telephone line. This is achieved by providing a billing signal sending circuit characterized in that the level of the signal current is reduced when the current polarity is reversed.

(θ) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention, where Trl is a transistor for controlling the line current, F is a filter for controlling the base current of Trl, Tr2 is a transistor for driving the MPIJ line, and LPF' is a low-pass filter. 12 is a power supply, C1 is a capacitor for noise cancellation, and the same members as in FIG. 1 are given the same reference numerals. FIG. 4 shows voltage or current waveforms at various parts in FIG. 3. In Figure 4,
Waveform ■ is the base input voltage of Tr2, waveform ■ is the input voltage of filter circuit F, waveform ■ is the base input current of Tri,
The waveform ■ is the input waveform of the LPF, and the waveform @ is the one-way current when the current flowing from ■ in FIG. 3 to ■ through the trunk circuit (OGT) of the exchange is set in the positive direction.

In the present invention, when transmitting charging pulses (polarity reversal), the line current is gradually decreased using a transistor, and when the line current reaches zero, the polarity is reversed, and then the line current is gradually increased to restore the original state. Then, the line current is gradually decreased again, and when the line current reaches zero, the polarity is restored. By using a simple LPF to remove the weak noise that occurs at this time, it is possible to This is an attempt to remove the noise.

The operation of an embodiment of the present invention will be explained below with reference to FIG. 3.During a telephone call, a billing signal as shown in FIG. 0 of FIG. 4 comes from the receiving side exchange. The width of Nokurusu in figure 0 is approximately 200zg
It is. In response to this signal, a waveform as shown in (■) in FIG. 4 is created (the pulse width of the waveform (■) is approximately 50 m5), and this is input to the filter circuit F (■ terminal) in FIG. 3.

As a result, the waveform becomes dull in the filter circuit wIF, and a smooth current with waveform (■) in Fig. 4 flows to the base of Trl in Fig. 3, gradually reducing the collector current of Try and reducing the current flowing through the communication line. When the voltage becomes zero, the waveform (2) in FIG. 4 is applied to the base (■ terminal) of Tr2 in FIG. 3 with a time delay, and as a result, the MP+7 relay is activated and the polarity of the communication line is reversed. When the polarity of the telephone line is reversed, no noise is generated because no current is flowing through the telephone line, as described above. Next, the second pulse of waveform (3) in FIG. 4 is applied to filter F, thereby gradually reducing the collector current of Tri. In this case the line lol! The current becomes a reverse current due to polarity reversal.

In this way, the MP relay is restored while the current in the communication circuit becomes zero again. By controlling the current waveform in this way, noise is significantly reduced, but the waveform remains with a slight but abrupt change point, as shown in waveform ① in Figure 4, which also becomes a source of noise. , 1. by LPF.
Creates a smoother waveform. LP? The line current waveform after passing through is waveform (■) in FIG. When inverting the polarity in this way, the noise can be reduced by not changing the line current suddenly but by changing it smoothly in steps.

Incidentally, a generating circuit for waveforms ① and Q in FIG. 4 is shown in FIG.

In FIG. 5, 1 is a delay circuit, 2 is a differentiating circuit, and 3 is a shaping circuit, to which a charging signal is applied to terminal a. The differentiating circuit 2 generates pulses at the start and stop points of the waveform (■), and these pulses are converted into the forming cycle W! 13, the waveform ■ shown in FIG. 4 is obtained from the terminal Cr. On the other hand, the waveform ■ applied to the delay circuit 1 is delayed by the pulse width of the waveform ■, and the waveform ■ shown in FIG. 3 is obtained. The reason why the waveform (2) applied to the line (2) is delayed by the pulse width of the waveform (2) is to change the waveform after the current in the communication line becomes zero.

According to the above explanation, upon receiving the billing signal of the waveform ■ in Fig. 4, the polarity of the telephone line is reversed for about 200 m5, and the OGT
This can be transmitted to the user and the noise can be significantly reduced.

(f) Effects of the Invention As described in detail above, the present invention has the great effect of reducing the noise generated when transmitting the charging signal in the charging signal sending circuit.

[Brief explanation of the drawing]

Figure 1 shows an example of a conventional billing signal sending circuit.
In the filter, coil L1 capacitor C1, 02, C
3, rQ and mp are both relays RL and MP.
This is the point of contact. C4 is a capacitor and HYB is a transformer. FIG. 2 shows all the voltage and current waveforms at each part of FIG. 1. FIG. 3 is a diagram showing an embodiment of the present invention. Trl in the diagram
#1 is approximately a transistor for current control, F is a filter for controlling the base current of Trl, Tr2 is a transistor for driving the MP relay, LPF is a low-pass filter for noise cancellation, E2 is a power supply, and C1 is a capacitor. Figure 4 shows the voltage or current waveforms at each part in Figure 3.
In the figure, the waveform ■ is the base input voltage of Tr2, and the waveform ■
is the input voltage of filter circuit F, waveform ■ is the base input current of Trl, shaping ■ is the input waveform of LPF, waveform ■ is the third
From ■ in the diagram to the trunk circuit (OGT) of the exchange ■
This is the line current when the current flowing to is in the positive direction. FIG. 5 is a block diagram of a circuit that creates some of the waveforms used in the present invention. Figure 3 Figure 5 Figure 324- 躬4 圀

Claims (1)

[Claims] In a system in which all polarity reversal pulses sent from the receiving exchange are relayed to the transmitting exchange, a low-pass filter is placed between the contacts of the polarity reversal relay and the communication line, and a switching filter is placed between the polarity reversal relay and the power supply. By arranging transistors respectively and operating the switching transistors immediately before the rising and falling edges of the polarity inversion pulse, the level of the signal current flowing through the communication line is reduced when the polarity of the signal current is reversed. billing signal sending circuit.