JPS62233961A - Pb dial interface circuit - Google Patents

Abstract

PURPOSE:To decrease remarkably the delay in the signal transmission and the momentary interruption of a line at PB sending by operating a voltage comparator circuit at PB dialing so as to short-circuit of a resistor of a CR balanced power supply circuit. CONSTITUTION:Resistors R1, R2, a side tone balancing circuit network 3, a reception amplifier 7, a voltage comparator circuit 8, an electronic switch circuit (ES) 9 and a transmission amplifier 4 are connected to line terminals (LA, LB) l, 2 and an output voltage VT' of a power supply circuit (N) 43 is fed as a DC power supply for a PB dial interface circuit 5 and a PB dial oscillator 6. In depressing a dial at PB dialing, a level of a terminal M is made active, a transistor (TR) T6 is turend on, a differential circuit comprising TRs T2-T5 is operated, a TR T1 of the ES 9 is turned on to short-circuit R3 thereby quickening the charging to a capacitor C, the output voltage VT' of the circuit N 43 rises to turn off the ES 9. Thus, the leading of the voltage between the terminals LA1 and LB2 is quickened by decreasing the line momentary interruption time.

Description

[Detailed Description of the Invention] Field of Industrial Application] The present invention relates to a PB dial interface circuit, and more particularly to a PB dial interface circuit that improves the oscillation characteristics when making a PB dial call in a telephone network with a PB dial interface circuit. Conventional technology] Conventionally, in this type of PB dial interface circuit,
Since a commercially available PB dial integrated circuit is used as the PB dial transmission circuit, it is necessary to use a higher power supply voltage when making a PB dial call than when making a call.

FIG. 2 is a circuit diagram showing an example of a conventional telephone communication network with a dial interface circuit, and FIG. 3(a) is a waveform diagram between line terminals during transmission in FIG. 2.
A resistor R1, a resistor R2, and a sidetone balancing circuit (hereinafter referred to as Z) 3 are connected in series to the line terminals (LA, LB) 1.2, and a signal is sent between the connection point of the resistors R2 and R2 and LB2. A speech amplifier (hereinafter referred to as TA) 4 is connected. TA4 consists of an output amplifier (hereinafter referred to as A1) 40, a pre-stage amplifier (hereinafter referred to as A2) 41, a switch (hereinafter referred to as 5W) 42, and a power supply circuit (hereinafter referred to as N) 43 using a CR smoothing circuit.

N43 is composed of resistor R3 and capacitor C, and its output voltage ■□゛ is connected to A241, PB dial interface circuit (hereinafter referred to as PI) 5, and PB dial oscillation! i1(
5W42 is connected to the output voltage V' and the power terminal of A241 and is normally in the on state, but when 03C6 is activated when making a PB dial call. The M terminal is turned on and 5
W42 turns off and stops supplying power to A241.

Furthermore, a receiving amplifier (hereinafter referred to as RA) is installed between LAI and LB2.
) 7 is connected via a constant current source ■, and the output 0 of PI5 is connected to the input of transmitter A+40.

Here, when the PB dial is set to the transmission state, the M terminal is turned on by the operation of os06, 5W42 is turned off, and the output voltage VT' is 1% supplied to PI5 and 0SC6, and the PB dial is turned on.
The dial signal is PI5. LAN, LB through A+40
It will be sent out between 2. LS commercially available as OS (E ())
When I is used, the output voltage VT° needs to be 3V or more in order to stabilize the output signal, which is higher than during a call. In this example, l) When the DC characteristics change during B oscillation, the output of PI5 does not stabilize until the capacitor C is charged through the resistor R3 until the output voltage VT° rises, and the output of PI5 does not stabilize after the PB dial is pressed. It takes several ms until the output 0 occurs, and the waveform between LAI and LB2 is shown in Figure 3 (
As shown in a), there is a momentary interruption and a delay of several milliseconds occurs before stable output is obtained.

['Problem that the invention seeks to solve]

In the above-mentioned conventional communication circuit network with a PB dial interface circuit, when a PB dial is made, the DC characteristic increases, and the power supply circuit of the PB dial interface circuit and the transmitting amplifier is It takes time to charge the capacitor, and there is a momentary disconnection of the front line for a few milliseconds when the dial switch is pressed, so some exchanges may malfunction.

Means for Solving Problems] The PB dial interface circuit of the present invention includes a transmitting amplifier, a receiving amplifier, and a PB dial interface circuit, and has two resistances between two line terminals and a sidetone A balanced circuit network is connected in series, and the transmitting amplifier and the output of the PB dial interface circuit and the power supply circuit are connected between the connection point of the two resistors and the connection point of the sidetone balance network and the line terminal. In the connected 1] B dial interface circuit with communication circuit, an electronic switch circuit is connected in parallel between the voltage comparison circuit connected between the line terminals, the connection point of the two resistors, and the power supply circuit output terminal. An output of the power supply circuit and an input of the electronic switch circuit are connected to the input and output of the voltage comparison circuit, respectively.

〔Example] Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of a telephone communication network with a PB dial interface circuit showing an embodiment of the present invention, and FIG. 3 (1)) is a waveform diagram between line terminals during a call in FIG. 1.

In FIG. 1, the same components as in the conventional example are given the same reference numerals as in FIG. 2, and their explanations will be omitted. This embodiment is based on the conventional example of transistor T2. ~T5, a differential circuit consisting of a switch transistor T6. Diode D1 that constitutes the comparison power supply
D9. A voltage comparison circuit (hereinafter referred to as VC) consisting of resistors R5 and R6
O)8 and transistor T1. An electronic switch circuit (hereinafter referred to as ES) 9 consisting of a resistor R4 for preventing floating is added.

When the dial is pressed when transmitting PI3, the M terminal is turned on, transistor T6 is turned on, and the differential circuit of transistors T2 and T3 is operated. , when the dial is pressed, the output voltage VT' of N43 is about 2■ to maintain the talking state, and I
- A current of 7fn is applied to the transistor T3 side, and the transistor T1 of BS9 is turned on to short-circuit the resistor R8, accelerating the charging of the capacitor C/\ and hastening the rise of the output voltage vT''. Power rise VT” > VB
(approximately 3.25V), the differential circuit has a transistor T21! ]! Since current flows through I, ES9 is turned off. Therefore, when the dial is pressed, the voltage between LAI and LB2 becomes as shown in FIG. 3(b), and the instantaneous line interruption time is shortened and the voltage rises quickly compared to the conventional circuit.

〔Effect of the invention〕

As explained above, the present invention operates the voltage comparator circuit when making a Pa dial call and short-circuits the resistance of the CR balanced power supply circuit, thereby speedily changing the DC state from the DC state during a call to the DC state when making a Pa dial call. This has the effect of significantly reducing line interruptions and signal transmission delays during PB transmission.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a telephone network with a PB dial interface circuit showing an embodiment of the present invention, and Fig. 2 is a circuit diagram of a conventional PB dial interface circuit.
A circuit diagram showing an example of a telephone communication network with a dial interface circuit, and FIG. 3 (a> and (one)) are waveform diagrams between line terminals during transmission in FIGS. 1 and 2, respectively. 1.2 ...Line terminal (LA, LB), 3.0. Sidetone balance circuit network (Z), 4.Talking amplifier (TA)-5.
...PB dial interface circuit (PI), 6...
・P B dial oscillator (O3C), 7... Receiving amplifier (RA>, 8... Voltage comparison circuit (■CO), 9...
・Electronic switch circuit (ES>, 40...output amplifier (
AI), 41... Pre-stage amplifier (A2), 42... Switch (SW), 43... Power supply circuit (N), C...
・Capacitor, ■)1. 〜D、・・・Guioto、■・
・・Constant current source, R1, ~R6 ・・Resistor, T1. ~T5
...transistor, T6...switch transistor.

Claims (1)

[Claims] A transmitting amplifier, a receiving amplifier, and a dial interface circuit are provided, and two resistors and a sidetone balancing circuit are connected in series between two line terminals, and a connection point between the two resistors and a side tone balancing circuit are connected in series between two line terminals. In a communication circuit network with a PB dial interface circuit, in which the transmitting amplifier and the output and power supply circuit of the PB dial interface circuit are connected between the connection points between the sound balance circuit network and the line terminals, and an electronic switch circuit in which an electronic switch circuit is connected in parallel between the connection point of the two resistors and the power supply circuit output terminal, and the power supply circuit is connected to the input and output of the voltage comparison circuit, respectively. A PB characterized in that the output of the electronic switch circuit and the input of the electronic switch circuit are connected to each other.
Dial interface circuit.