JPS637704B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a howler sound transmission circuit in a telephone exchange.

In a conventional howler sound transmission circuit, the amount of attenuation of the alternating current signal from the signal source is sequentially reduced over time, and the volume is sequentially increased.

Generally, this attenuation amount is controlled by sequentially shorting the resistors, and the contacts of a relay are used for each short circuit. In order to control the operation timing of this relay, the timing is either received from the outside or a timing circuit is formed using the relay. The former case requires external timing control means, and the latter case requires a large number of relays. However, in recent years, there has been a growing demand for miniaturization through computerization, so the present invention provides a howler sound sending circuit that eliminates the need for the above-mentioned relay and changes the amount of attenuation over time within its own circuit.

The present invention will be explained in more detail below with reference to the drawings. FIG. 1 shows a conventional howler sound sending circuit, and FIG. 2 shows its current waveform. Here, if a subscriber holds the handset up for a certain period of time, for example 50 seconds or more, the control device of the exchange detects this and connects that subscriber to the howler sound transmission circuit shown in Figure 1. . At this time, A relay operates. On the other hand, _the signal source SIG constantly sends out the 800 Hz continuous signal shown in Figure _{2 A} , but in this state the subscriber I can barely hear the howling sound. If the subscriber still raises the handset even after several seconds have elapsed from this state, a control device (not shown) drives relay X via the signal distribution device SD. As a result, the resistor R ₁ is short-circuited, and a small-amplitude Hauler signal is given to the telephone TEL side. This state is the state shown in FIG. 2B. Furthermore, after a few seconds have elapsed, relay Y is driven in the same manner as described above, and resistors R ₁ ,
R ₂ is shorted. As a result, a howler signal with a larger amplitude than before is given to the telephone TEL side.
This state is the state shown in FIG. 2B. Furthermore,
When the time has elapsed, relay Z is activated and a howler sound of maximum amplitude is given to the telephone TEL. This state is the state shown in FIG. 2B. If the handset of the telephone TEL (not shown) is turned down during the elapse of these times, the A relay will be restored, and the control device (not shown) that monitors the operating status of this A relay will send out a howler sound. will be stopped.

In this way, the conventional howler sound transmission circuit uses relays (X, Y, Z), which is not suitable for computerization, and since relays X, Y, and Z are all controlled by the control device, the control device This is undesirable as the load increases. The present invention has improved this drawback by applying a predetermined potential alternately to both ends of the winding on the primary side of the transformer as a signal source for howler sound, and from the midpoint of the winding to a transistor circuit for supplying current. The howler sound sending circuit is connected to a ground power supply via a ground power supply, and induces an output voltage on the secondary side of the transformer by a potential difference between the ground power supply and the potential at one end of the winding, and is connected to a feedback circuit of an operational amplifier. The current flowing through the transistor circuit is controlled by changing the base potential of the transistor circuit using a time-voltage conversion circuit provided with a capacitor, thereby controlling the output voltage induced on the secondary side of the transformer.

FIG. 3 shows a howler sound transmission circuit according to an embodiment of the present invention, and the signal source for the howler sound is an input terminal.
Connected to I ₁ and I ₂ . _The signal from this signal source is transmitted via the transformer T to its _secondary output terminals O ₁ ,
transmitted to _O2 . These output terminals O ₁ and O ₂ are connected to a telephone set. As in FIG. 1, when a subscriber holds the handset up for a certain period of time, the howler sound sending circuit is connected to the subscriber's telephone. As a result, the A relay (not shown) operates, its contact a ₁ closes, and the output of the time-voltage conversion circuit CT controls the transistor circuits Q ₁ and Q ₂ to control howler sound transmission to the subscriber. be exposed. This time-voltage conversion circuit CT has the following configuration. For negative power supply V _B , Zener diode D ₁ ,
Create the control voltage to the operational amplifier AMP with D ₂ . That is, the Zener diode D ₁ is connected to the V _CC of the amplifier AMP.
Zener diode D ₂ gives the V _ee voltage. A series circuit of resistors _R4 and _R6 is connected in parallel to the Zener diode _D1 , and one end of the resistor _R4 is connected to the negative input of the amplifier AMP via the resistor _R3 . Further, the connection point between resistors _R4 and _R6 is connected to the positive input of the amplifier AMP via resistor _R5 . Furthermore, a feedback circuit is provided from the output of the amplifier AMP to the negative input, and this feedback circuit is a series circuit of a resistor R ₂ and a capacitor C, and
A parallel circuit of a ₂ and a resistor R ₁ is connected in parallel to the capacitor C as a discharge circuit for the capacitor C.
As a result, when contact _a2 is inactive, that is, when this howler sound sending circuit is not connected to the telephone, the amplifier is activated by the values of resistors _R1 , _R2 , _R3 , _R4 , _R5 , and _R6
The initial value of the AMP output voltage is determined. However,
As mentioned above, when this howler sound transmission circuit is used and its contact _a2 opens due to the operation of relay A (not shown), charging current flows to capacitor C, and resistor _R2 ,
The voltage drop rate of the amplifier AMP is controlled by the values of R ₃ , R ₄ , R ₆ and capacitor C, and the potential at point P gradually drops. Therefore, when the potential at point P becomes less than the Zener voltage of the Zener diode _D0 ,
Transistor Q ₂ is turned on, and accordingly transistor Q ₁ is also turned on. Thereafter, the output current of the transistor _Q1 is controlled to gradually increase in accordance with the potential drop at point P. Figure 5 shows the potential state at point P, with time (seconds) on the horizontal axis;
The vertical axis shows the potential. That is, if the moment when contact _a2 opens is _t0 , then the potential at point P is _V0 , but it gradually decreases and reaches the Zener voltage at time _t1 .
Reach V _z . Then, the potential drop at point P continues until time _t2 and does not change thereafter. As a result, the current from the transistor Q ₁ gradually increases from time t ₁ to t ₂ and remains constant thereafter. Also, transformer T
The howler sound signal shown in FIG. 4 is constantly applied to the input terminals I ₁ and I ₂ connected to the primary side of the input terminals I 1 and I 2 . In other words, A in the figure shows the signal waveform applied to the input terminal _I1 ,
B is a signal waveform applied to the input terminal _I2 , which is a rectangular wave whose phase is shifted by 180 degrees. Note that this frequency is 800Hz. That is, the power supply at a given potential is 800
It is applied alternately to input terminals I ₁ and I ₂ at Hz.
Therefore, the signals applied to the input terminals I ₁ and I ₂ appear as alternating current signals at the output terminals O ₁ and O ₂ via the transformer T in accordance with the current from the transistor Q ₁ .
FIG. 6 shows the amplitude, or voltage value, of the signals appearing at the output terminals O ₁ and O ₂ .

In Figure 6, the horizontal axis shows time (seconds), the vertical axis shows potential,
No signals appear at the output terminals O ₁ and O ₂ until time t ₁ . However, a voltage signal that gradually increases according to the illustrated curve from time t ₁ to t ₂ is obtained, and becomes constant after time t ₂ . That is, the howling sound heard from the telephone gradually becomes louder from time _t1 to time _t2 , and remains constant thereafter. This maximum voltage value Vm is the commonly used 75 volts.

As explained above, the howler sound transmission circuit of the present invention can be electronically implemented and is suitable for miniaturization, and has improved reliability, consumes less current, and generates less heat. Furthermore, it is possible to automatically control howler sound increase, and
It is extremely effective, as the volume increases smoothly.

[Brief explanation of the drawing]

Figures 1 and 2 are conventional examples, Figure 3 is an embodiment of the present invention, Figure 4 is the signal waveform of the howler sound signal source used in Figure 3, and Figure 5 is the time period in Figure 3. The output waveform of the voltage conversion circuit, FIG. 6 is a diagram showing the output voltage state of the circuit of FIG. 3. In the figure, CT is a time-voltage conversion circuit, AMP is an operational amplifier, R ₁ to _{R 8} are resistors, D ₀ to _{D 2} are Zener diodes, C is a capacitor, a ₁ and a ₂ are relay contacts,
Q ₁ and Q ₂ are transistors, T is a transformer, V _z is a Zener diode, and D ₀ is the Zener voltage.

Claims (1)

[Claims] 1. A predetermined potential is alternately applied to both ends of the winding on the primary side of the transformer as a signal source for howler sound, and a ground power source is connected from the midpoint of the winding through a transistor circuit for supplying current. A howler sound transmitting circuit that is connected to the earth power source and the potential of either end of the winding to induce an output voltage on the secondary side of the transformer, wherein a capacitor is provided in the feedback circuit of the operational amplifier. A howler sound transmitting circuit, characterized in that a voltage conversion circuit changes the base potential of the transistor circuit to control the current flowing through the transistor circuit, thereby controlling the output voltage induced on the secondary side of the transformer.