JPH0255445A - Telephone set circuit - Google Patents

Abstract

PURPOSE:To prevent an incoming circuit from being malfunctioned by a call signal from a dial speech circuit even if a telephone line of any line condition is connected by providing a reference voltage control circuit switching a reference voltage into a prescribed voltage higher than a voltage applied to the telephone line. CONSTITUTION:When a telephone set is hooked off and a DP signal is outputted from a dial/speech circuit 2, the signal is rectified and smoothed by a diode bridge DB 2 and smooth circuit 32 and the result is inputted to a comparator circuit 33. In this case, the voltage reaches a voltage lower than the voltage receiving an incoming signal, that is, a low voltage than a reference voltage V1. Thus, the comparator circuit 33 outputs an L level signal and a transistor(TR) Q2 is turned off. Thus, a photocoupler PH is turned off and only a resistor R11 is connected between an RSL and a GND terminal of the incoming circuit 1, and a higher voltage than the voltage between lines L1 and L2 is set. Thus, the incoming circuit I is not operated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a telephone equipped with a call receiving circuit that operates when the voltage supplied to the telephone line is equal to or higher than a reference voltage.

(Conventional technology) FIG. 2 is a block diagram showing an example of a conventional telephone circuit.

In the figure, 1 is an incoming call circuit that rings a bell, etc. Reference numeral 2 denotes a calling/talking circuit which generates a dial pulse signal and converts an audio signal into an electrical signal. Ll and L2 are connection terminals to the telephone line. The connection terminal L1 is connected to one end side input terminal of the first diode bridge DBI via a capacitor C1 and a resistor R1 connected in series, and the connection terminal L2 is connected to one end side input terminal of the first diode bridge DB1. Connected to the other end input terminal. The output terminal of the first diode bridge DBI is a Zener diode Z
It is connected to the input terminals Vcc and GND of the receiving circuit 1 via a smoothing circuit consisting of D1 and a capacitor c2. Further, a resistor R2 is connected between the reference voltage adjustment terminal R8L of the incoming circuit 1 and the other end input terminal GND, and the operating reference voltage of the incoming circuit 1 is set by the resistor R2. This operating reference voltage is high when the value of the resistor R2 is large.

Further, the connection terminal L] is connected to one end side input terminal of the second diode bridge DB2 via a hook switch H8, and the connection terminal L2 is connected to the other end side input terminal of the second diode bridge DB2. ing. Further, the output terminal of the second diode bridge DB2 is connected to the input/output terminals LINI and LIN2 of the calling/talking circuit 2.

According to the telephone circuit, the telephone line connects the connection terminals Ll, L
An incoming signal input from the telephone line is rectified and smoothed into a DC signal through the first diode bridge DB1, the Zener diode ZDI, and the capacitor C2.

The incoming circuit 1 inputs the DC signal and connects the resistor R.
The operating reference voltage set in step 2 is compared with the voltage of the DC signal. As a result, when the voltage of the DC signal is equal to or higher than the operating reference voltage, the receiving circuit 1 operates and rings the bell.

(Problem to be solved by the invention) However, in the conventional telephone circuit, the incoming signal and the outgoing
Since there is no means to distinguish between the outgoing signal and the outgoing signal from the communication circuit 2, the line condition of the telephone line connected to the connection terminals Ll and L2 is poor, for example, when three telephones are connected in a branched manner. However, there was a problem in that the receiving circuit 1 was activated by the outgoing signal.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a telephone circuit in which the receiving circuit does not operate due to the outgoing signal from the outgoing/talking circuit, no matter what line conditions the telephone line is connected to. .

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a telephone circuit including an incoming call circuit that operates when the voltage supplied to the telephone line is equal to or higher than a reference voltage. a voltage detection circuit that inputs the voltage supplied to the telephone line and compares the voltage with a predetermined voltage; and a voltage detection circuit that inputs the voltage supplied to the telephone line and compares the voltage with a predetermined voltage; A reference voltage control circuit is provided for switching to a higher predetermined voltage or a predetermined voltage lower than the voltage being supplied to the telephone line.

(Function) According to the present invention, the voltage detection circuit compares the voltage supplied to the telephone line with a predetermined voltage, and the reference voltage control circuit adjusts the reference voltage based on the comparison result of the voltage detection circuit. is switched to a predetermined voltage higher than the voltage supplied to the telephone line or to a predetermined voltage lower than the voltage supplied to the telephone line.

(Example) FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figures, the same components as those of the conventional example are represented by the same reference numerals. That is, 1 is the incoming circuit, 2 is the outgoing/talking circuit, and 3
4 is a voltage detection circuit, and 4 is a reference voltage control circuit. Also L
l and L2 are connection terminals to the telephone line, and the connection terminal L1
is connected to one end side input terminal of the first diode bridge DBI via a capacitor C1 and a resistor R1 connected in series. Further, the connection terminal L2 is connected to the other end side input terminal of the first diode bridge DB2, and the output terminal of the first diode bridge DBI is connected to the incoming signal via a smoothing circuit consisting of a Zener diode ZD1 and a capacitor c2. The input terminal Vcc of the circuit 1 is connected to GND. Further, the reference voltage control circuit 4 is connected between the reference voltage adjustment terminal R8L of the incoming call circuit and the other end input terminal GND. The reference voltage control circuit 4
is composed of resistors RIO, R11 and a light receiving part of a photocoupler PH, and is connected to the reference voltage adjustment terminal R8 of the incoming circuit 1.
The resistor R11 is connected between L and the other end side input terminal GND, and the resistor RIO and the light receiving part of the photocoupler PH, which are connected in series, are connected in parallel to the resistor R11.

Further, the connection terminal L1 is connected to one end side input terminal of the second diode bridge DB2, and the connection terminal L2
is connected to the other end input terminal of the second diode bridge DB2. Further, the positive output terminal of the second diode bridge DB2 is connected to one end side input terminal of the voltage detection circuit 3, and the hook switch H8
It is connected to one end side input terminal of the calling/talking circuit 2 via. Further, the second diode bridge DB2
The negative output terminal of is connected to the other end input terminal of the voltage detection circuit 3 and the other end input terminal of the calling/talking circuit 2.

The voltage detection circuit 3 includes a rectifying circuit 31 consisting of a resistor R3 and a diode D1 connected in series, a smoothing circuit 32 consisting of a capacitor C3, a Zener diode ZD2, and a resistor R4 connected in parallel, and a resistor. R5, R6, R
7 and an operational amplifier Q1, and a first coupler drive circuit 34 consisting of a capacitor C4, resistors R8 and R9, a transistor Q2, and a light emitting section of a photocoupler PH. The positive output terminal of the second diode bridge DB2 is connected to the rectifier circuit 31.
It is connected to the positive electrode side of the smoothing circuit 32 through the terminal, and is also connected to the input terminal of the operational amplifier Q1 of the comparison circuit 33. Further, the negative side of the smoothing circuit 32 is connected to the negative side output terminal of the second diode bridge DB2. One input terminal of the operational amplifier Q1 is connected to the negative electrode side of the smoothing circuit 32 via a resistor R5, and is also connected to a +5V power supply (not shown) via a resistor R6. As a result, one input terminal of the operational amplifier Q1 receives the reference voltage V1 divided by the resistors R5 and R6.
is input. Further, the output terminal of the operational amplifier Q1 is connected to the base of the transistor Q2 of the photocoupler drive circuit 34 via a resistor R7. A capacitor C is connected between the base and emitter of the transistor Q2.
4 and resistor R8 are connected in parallel, and the transistor Q
The emitter of No. 2 is connected to the negative electrode side of the smoothing circuit 32. Further, the collector of the transistor Q2 is connected to a +5V power supply (not shown) via a light emitting part of a photocoupler PH and a resistor R9.

The operational amplifier Q1 of the comparator circuit 33 outputs a high level signal when the voltage at the 10th input terminal becomes equal to or higher than the voltage at the 1st input terminal, and outputs a low level signal when the voltage at the 10th input terminal becomes lower than the voltage at the 1st input terminal. Output.

Next, the operation of the telephone circuit of the present invention will be explained based on the signal waveform diagram shown in FIG.

When an incoming call signal IR is input to the telephone circuit, the connection terminal L1. The voltage between L2 is the DC component VD and the incoming signal IR.
is the sum of the voltages. At this time, the signal A input to the incoming circuit 1 is obtained by rectifying and smoothing the incoming signal ■R by the first diode bridge DBI, the Zener diode ZD1, and the capacitor C2. That is, the signal input to the first diode bridge DBI is converted into an AC signal by the capacitor C1. Further, a signal that is the sum of the incoming signal IR and the DC component VD is input to the voltage detection circuit 3 after being rectified by the second diode bridge DB2. The voltage detection circuit 3
The signal input to the comparator circuit 33 is rectified and smoothed by the rectifier circuit 31 and the smoothing circuit 32 as a signal B.
is input. In the comparison circuit 33, the voltage of the signal B and the reference voltage v1 are compared, and since the voltage of the signal B is higher than the reference voltage V1, the output of the operational amplifier Q1 becomes high level. As a result, the transistor Q2 of the photocoupler drive circuit 34 is turned on, the light emitting section of the photocoupler PH is energized, and the phototransistor of the light receiving section of the photocoupler PH is turned on. As a result, the resistor RIO and the resistor R11 of the reference voltage control circuit 4 are connected in parallel to have a low resistance value, and the operating reference voltage of the incoming circuit 1 is applied between the connection terminals Ll and L2. Since the voltage becomes lower than the voltage, the incoming call circuit 1 is activated and the bell rings.

Furthermore, when making a call with the telephone set off-hook, the DC component VD of the voltage between the connection terminals Ll and L2 is much lower than that in the on-hook state. An oscillation signal DP is output from. At this time, the signal A input to the incoming circuit 1 is obtained by rectifying and smoothing the outgoing signal DP by the first diode bridge DBI, the Zener diode ZDI, and the capacitor C2. Further, a signal that is the sum of the DC component VD and the oscillation signal DP is input to the voltage detection circuit 3 after being rectified by the second diode bridge DB2. The signal input to the voltage detection circuit 3 is
The signal B is rectified and smoothed by the rectifier circuit 31 and the smoothing circuit 32, and is input to the comparison circuit 33. In the comparison circuit 33, the voltage of the signal B and the reference voltage V1 are compared. In this case, unlike when receiving the incoming signal IR, the DC component VD of the voltage between the connection terminals Ll and L2 is a low voltage, so the voltage of the signal B becomes a voltage lower than the reference voltage V1.

Therefore, the output of the operational amplifier Q1 becomes low level. As a result, the transistor Q2 of the photocoupler drive circuit 34 is turned off, the light emitting section of the photocoupler PH is no longer energized, and the phototransistor of the light receiving section of the photocoupler PH is turned off. As a result, the reference voltage adjustment terminal R8L of the incoming call circuit 1 and the other end side input terminal G
Only the resistor R11 is connected between it and ND. As a result, the operating reference voltage of the receiving circuit 1 is set higher than the voltage applied between the connecting terminals Ll and L2, so the receiving circuit 1 does not operate and the bell does not ring.

(Effects of the Invention) As explained above, according to the present invention, in a telephone circuit including an incoming call circuit that operates when the voltage supplied to the telephone line is equal to or higher than a reference voltage, the voltage supplied to the telephone line is a voltage detection circuit that inputs a voltage and compares the voltage with a predetermined voltage; and a voltage detection circuit that inputs a voltage and compares the voltage with a predetermined voltage; and a voltage detection circuit that sets the reference voltage to a predetermined voltage higher than the voltage supplied to the telephone line or Since a reference voltage control circuit that switches to a predetermined voltage lower than the voltage supplied to the telephone line is provided, it is possible to distinguish between an incoming signal and an outgoing signal, and the incoming circuit is activated only by the incoming signal. Therefore, no matter what kind of line condition the telephone line is connected to the telephone set, the incoming call circuit is activated by the outgoing signal and the bell will not ring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing an example of a conventional telephone, and FIG. 3 is a signal waveform diagram in one embodiment of the present invention. 1... Incoming circuit, 2... Outgoing/talking circuit, 3...
Voltage detection circuit, 4... Reference voltage control circuit, 31...
Rectifier circuit, 32... Smoothing circuit, 33... Comparison circuit,
34...Photocoupler drive circuit. Patent Applicant Oki Electric Industry Co., Ltd. Agent Patent Attorney Yoshi 1) Takashi Sei

Claims (1)

[Claims] In a telephone circuit including a call receiving circuit that operates when the voltage supplied to the telephone line is equal to or higher than a reference voltage, the voltage supplied to the telephone line is input and the voltage is set to a predetermined value. a voltage detection circuit that performs a comparison with a voltage; and a voltage detection circuit that sets the reference voltage to a predetermined voltage higher than the voltage supplied to the telephone line or lower than the voltage supplied to the telephone line based on the comparison result of the voltage detection circuit. 1. A telephone circuit comprising a reference voltage control circuit for switching to a lower predetermined voltage.