JPS6316197Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in reducing alternating current loss during telephone calls in telephones using electronic pulse dialing.

In conventional telephone circuits, when making a call, a low-value resistor was inserted in the circuit parallel to the telephone network, so the circuit parallel to the telephone network had low impedance, resulting in large AC losses.

The present invention solves the above-mentioned drawbacks and reduces AC loss during telephone calls.

Figure 1 shows a conventional telephone circuit using a pulse dial IC.

DC ₄₈ V is applied to the L ₁ and L ₂ terminals from the exchanger. When you take off the handset, switch 1 closes, and when ₄₈ VDC passes through bridge diode 2,
The voltage becomes a constant polarity voltage, passes through the resistor 3 and the reverse current prevention diode 4, and is charged to the capacitor 5. The charging voltage provides an operating power between the power terminals VDD and VSS of the IC 6, and at the same time is applied to a differentiating circuit consisting of a capacitor and a resistor 7 to generate a pulse voltage.
When this pulse voltage is applied between HS and VSS of IC6, IC6 is reset. Subsequently, an H voltage appears at the dial pulse output terminal, that is, the DP terminal of the IC 6, which causes the transistor 9, which is an NPN transistor, to conduct through the resistor 8, and further to conduct the pulse relay transistor 11, which is a PNP transistor, through the resistor 10. The conduction of transistor 11 energizes telephone communication circuitry 13, and the telephone enters a calling state to the exchange. Afterwards IC6
The voltage between VDD and VSS is supplied through a resistor 12 and a backflow prevention diode 4. Here, the resistance of the resistor 12 is lower than that of the resistor 3.

Next, by pressing any number 0 to 1 on the push button switch 14, the dial number is input to the IC 6, and at the same time, the reference frequency determined by the resistor and capacitor 15 is oscillated, and the frequency is divided and processed.
A dial output with alternating high and low voltages appears on the DP terminal. This output causes transistor 11 to turn ON and OFF repeatedly through transistor 9, and a dial pulse is sent to the exchange.

The above is an explanation of the operation of the conventional circuit, and next, improvements will be described.

First, regarding the insertion AC loss of the dial, in Figure 1, resistors 10 and 12 have a loss of approximately 2.3 dB during a call.
give a loss. Here, resistor 3 is 150KΩ, so ignore it. Resistor 10 and resistor 12 are respectively
It is 2KΩ, and if you calculate the parallel combined resistance, it becomes 1KΩ. This 1KΩ is the nominal impedance of the phone 600
The loss due to being inserted in parallel with Ω is approximately 2.3dB.
According to domestic technical standards, it must be kept below 1 dB.

In addition, when making a call after taking off the handset, IC6, which makes up the electronic pulse dial, must first be reset, but with the conventional circuit, sufficient reset voltage cannot be obtained, so subsequent dialing cannot be made. Sometimes.

This is because the voltage applied to the differentiating circuit 7 rises slowly. That is, the charging time constant of the resistor 3 and capacitor 5 must be considerably larger than the time constant of the differentiating circuit. The above are the drawbacks of the conventional circuit.

FIG. 2 is a circuit diagram of a telephone equipped with a pulse dial IC, which is an embodiment of the present invention. When you take off the handset, the switch 1 closes and the capacitor 5 is charged by ₄₈ V DC, and the charging voltage increases to the voltage of the IC 6.
The explanation up to the point where the operating power is applied between VDD and VSS is the same as the explanation in FIG. 1. Since the charging voltage simultaneously applies a reset voltage between HS and VSS of IC6 through the resistor 7A, IC6 is reliably reset.
At this point, when you first disconnect the handset, the hook switch 7
F is closed, but the time constant of the integrating circuit composed of resistor 7C and capacitor 7E keeps transistor 7B non-conductive until a sufficient reset voltage is reached. Thereafter, the transistor 7B is turned on and the voltage between HS and VSS of the IC 6 is maintained at the L potential through the switch 7F. The resistor 7D has a high resistance and is used to discharge the charge in the capacitor 7E after the end of the call. Also, in the hooking operation (momentarily turning off the switch 1 and 7F) to make a call again, the IC 6 is reliably reset because the switch 7F is turned off. As mentioned above, when an initial reset is applied to the IC 6, the transistor switch 7B is controlled by a time constant consisting of a resistor 7C and a capacitor 7E, and when a reset is applied at the time of hooking, the transistor switch 7F is forcibly disconnected. Here, the switch 7F can be replaced with a transistor switch or the like that operates in conjunction with the switch. Next, during a call, the resistor 10 shown in Figure 1 is
In place of the resistor 12 and the resistor 12, constant current diodes 10A and 12A are used in FIG. 2, respectively.
When the rated DC current is applied to a constant current diode, the AC impedance of this element is several 100KΩ.
Therefore, by using a constant current diode instead of a resistor that causes AC loss, AC loss can be easily reduced, and even in the improved example shown in Figure 2, insertion AC loss can be reduced.
Can be suppressed to 1dB or less.

As described above, the present invention improves the clarity and intelligibility of calls by reducing AC loss during calls by using constant current diodes.

[Brief explanation of the drawing]

Figure 1 shows a conventional telephone circuit using a pulse dial IC. FIG. 2 is a circuit diagram of a telephone equipped with a pulse dial IC, which is an embodiment of the present invention. 1...Full switch, 6...Pulse dial
IC, 7... Differential circuit, 7A... Resistor, 7B...
Transistor, 7C... Resistor, 7D... Resistor, 7
E... Capacitor, 7F... Hook switch, 1
0...Resistance, 10A... Constant current diode, 11
...Pulse relay transistor, 12...Resistor,
12A...constant current diode, 13...telephone circuit network.

Claims (1)

[Scope of utility model registration request] The voltage from the exchange is made into a constant polarity voltage and is supplied to the telephone network via the PNP transistor for pulse relay.In a telephone equipped with a pulse dial IC, the connection point between the PNP transistor and the telephone network, and the input power supply The PNP transistor for pulse relay is controlled via the NPN transistor by the output from the dial pulse output terminal of the pulse dial IC or between the power supply terminal (VDD) of the pulse dial IC, which has a capacitor connected in parallel for stabilization. for relay in this circuit
A telephone circuit characterized in that a constant current diode is inserted between at least one of the base of the PNP transistor and the collector of the NPN transistor to reduce alternating current loss during calls.