KR880003782Y1 - Automatic hold release circuit of telephone - Google Patents

Abstract

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Description

Automatic hold release circuit of the phone

1 is an automatic hold release circuit block diagram according to the present invention.

2 is a concrete circuit diagram of the block diagram of FIG.

3 is a timing diagram illustrating the operation of FIG.

* Explanation of symbols for main parts of the drawings

1: hold switching circuit 2: line sensing circuit

3: hold control circuit 4: call circuit

5: hook switch 6: melody integrated circuit

7 mute wire 8: ringer circuit

10: Hold switch

The present invention relates to an automatic hold release circuit in a telephone, and more particularly to a circuit for automatically releasing a standby state by lifting a hand cell while the telephone user waits for a telephone line.

In the office or home using the same trunk line number, a number of branches are installed so that the telephones are connected in parallel, and when the telephone rings, the call is made through one of the telephones. If the caller is not the caller, the caller is turned on and the caller is notified that the caller is on the phone. Lower the telephone handcell to its original position on the telephone.

In order to alleviate this inconvenience, there is a method of introducing a switch system for private exchange or branch connection to a large office, or using a telephone with an exchange function, but it is expensive to install or purchase such a telephone. do.

On the other hand, as a means for connecting a callee to a normal telephone or waiting for a telephone call for a predetermined time, there has conventionally been a method of mechanically holding a telephone line by a locking switch.

However, in the mechanical type using such a lock type switch, the caller has to turn on the hold switch until the call is made with the desired person, and when the call is made again, the hold switch is inconvenient.

Accordingly, an object of the present invention is to provide an electronic automatic hold release circuit that holds a telephone line by a single touch of a hold switch and does not store even when the hand cell is placed in its original position.

Another object of the present invention is to provide an electronic automatic hold release circuit capable of making a call by lifting a hand cell without restoring the hold switch when re-calling.

Therefore, in order to achieve the object of the present invention, a hold switching circuit for turning on the demister by a single press of the hold switch, a line sensing circuit for detecting the off state of the hook switch, and a standby state by the output of the line sensing circuit. Characterized in that it consists of a hold control circuit that can hold the trunk line.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a block diagram of an automatic hold release circuit of a telephone according to the present invention, which includes trunk lines L1 and L2, a normal call circuit 4 and a ringer circuit 8, a hold switching circuit 1, and a line sensing circuit. (2), the hold control circuit (3), and the hook switches (5) and (9).

The hook switch 5 of FIG. 1 in which the ordinary telephone is lowered is turned off, that is, the hook switch 5 is connected to the terminal b and the terminal C and is in a hook-on state.

In the above state, when the ring signal transmitted from the exchange to the trunk lines L1 and L2 arrives, it is input only to the ringer circuit 9. At this time, the ringer circuit 8, which inputs the 80Vrms 20HZ ring signal through the lines L1 and L2, converts the ring signal by an audible sound to ring the ring signal. As described above, when the telephone ring rings in the ringer circuit 8, the called party picks up the hand cell and asks the called party. At this time, the hook switch 5 is connected to the terminal c of the terminal a and becomes in an "on" state (hook-off state). If desired, the one-touch hold switch in the hold switching circuit (1) must be pressed.

When the one-touch hold switch in the hold switch circuit 1 is pressed as described above, the switching element in the hold switching circuit 1 is triggered. When the switching device of the hold switching circuit 1 is triggered, the line voltage of the trunk line L1 is input to the lime detection circuit 2 through the triggered switching device. The line sensing circuit 2 senses the voltage input of the trunk line L1 and outputs an output voltage of the "high" logic state to the hold control circuit 3. At this time, the high logic state is input by the hold control circuit 3 as a control signal to form the trunk line L1 in a loop with a domestic L2 through a switching element of the hold switching circuit 1 and a switch in the hold control circuit 3. . As described above, even when the hand cell is placed in the home position in a loop formed with the trunk lines L1 and L2, and the terminals b and c of the hook switch 5 are connected to the off state, the formed trunk line loop is not blocked but is waiting. will be held.

When the hook switch 5 is turned "on" (hook-off) in the holding state as described above, the voltage of the trunk line inputted to the trunk line L1 is triggered as described above. It is input to the line sensing circuit 2 and the hold control circuit 3 through the circuit, and also to the call circuit 4.

At this time, since the hold control circuit 3 and the call circuit 4 are connected in parallel, the hold voltage of the trunk line current loop formed through the hold switching circuit 1 and the hold control circuit 3 drops instantaneously.

As described above, the line sensing circuit 2 senses that the hold voltage is dropped instantaneously, and inputs a signal of the "low" state to the hold control circuit 3.

Thus, the hold control circuit 3 cuts off the current loop formed by the " low " output voltage of the line sensing circuit 2 so that the holding state is cut off, and the loop circuit in the known communication circuit 4 is closed. By the CO line L1, a new CO line 2 loop is newly formed to make a call. Therefore, the waiting state is automatically released and the call can be seen.

2 is a detailed circuit diagram of the block diagram of FIG. 1 according to the present invention, in which R1-R8 is a resistor, C1-C4 is a capacitor, SCR is a delister, D1 is a diode, LED is a light emitting diode, Q is a transistor, and OPA Denotes an operational amplifier, reference numeral 6 denotes a melody integrated circuit, reference numeral 7 denotes a line connected to the mute terminal of the call circuit 4, and the ringer circuit 8 connected between the trunk lines L1 and L2 is for convenience of explanation. Omitted for planning purposes.

3 is an operation waveform diagram for explaining the operation of FIG.

Now, as described above in FIG. 1, if a ring signal arrives at the trunk lines L1 and L2 and the user of the telephone configured as in FIG. 2 picks up the hand cell and wants to wait during a call, the terminal (a) of the hook switch 5 and (c) is connected and the state is "on" (hook-off). When the hold switch 10 of the hold switching circuit 1 is pressed and released once, the DC voltage on the trunk line L1 is changed to the trunk line L1, the hook switch 5, and the resistor R1. And it is input to the gate of the thyristor SCR through the hold switch 10 to trigger the thyristor SCR.

Here, the resistors R1 and R2 divide the DC voltage on the trunk line L1 into a predetermined level when the hold switch 10 is turned on, and input the resistance voltage to a gate of the demister SCR. The capacitor C1 is used to remove the impulse surge voltage. will be.

When the delister SCR is "on" at time t1 in FIG. 3, the voltage of the trunk line L1 is used as the power supply voltage of the operational amplifier OPA by the diode D1 and the smoothing capacitor C4 through the anode and the cathode of the delister SCR. The voltage of the trunk line L1 is divided by the resistors R3 and R5, and divided by the resistors R4 and R6 and input to the inverting terminals of the non-inverting terminals of the operational amplifier OPA, respectively.

At this time, the potential of the divided point A of the resistors R3 and R5 and the divided point B of the resistors R4 and R6 is adjusted to the voltage of the trunk line L1 when the hold switch 10 is pressed by adjusting the values of the resistors R3-R6. The voltage divider causes the non-inverting terminal input voltage of the operational amplifier OPA, that is, the voltage at the point A, to be greater than the voltage at the inverting terminal input voltage ie, the point B. A capacitor C2 is connected to the input of the inverting terminal (B) to charge the voltage.

Therefore, when the hold switch 10 is pressed, the waveform of the point (A) is as shown in FIG. 3 (a), and the waveform of the point (B) is the third (by the operation of the capacitor C2 connected in parallel with the resistor R6). b) becomes as shown.

Therefore, the comparison output of the operational amplifier OPA is output by the voltage of the trunk line L1 in the "high" state as shown in the third (d), and the output of the operational amplifier OPA is the resistance R9 of the hold control circuit (3). Through the capacitor C3 is charged as shown in (e) of FIG. 3 (e), the charging voltage of the capacitor C3 is input to the base of the transistor Q together with the bias voltage by the resistor R8 to turn on the transistor Q. That is, the capacitor C3 is pressed when the hold switch 10 is pressed (A) and (B) to compare the voltage is output to "high" as shown in (D) at the time of the third degree t1 from the operational amplifier OPA The instantaneous charging of the line sensing voltage by transient phenomenon is performed by the RC time constant as in (31) of the third (e), and when the charging by the RC time constant is completed, the voltage across the capacitor C3 is almost zero. The charging voltage of the capacitor C3 is input to the base of the transistor Q which is switched "on" by the bias voltage of the resistor R8 which inputs the output voltage output from the cathode of the demister SCR as shown in FIG. 3 (b) to one side. Thus, the transistor Q is driven.

At this time, after the transistor Q is turned on, the output of the operational amplifier OPA is blocked by the capacitor C3. Even if the bias voltage is continuously supplied to the base by the resistor R8 which inputs the output of the demister SCR, it is not turned off.

Therefore, the current path forms a loop between the trunk line L1 and the "on" triggered delister SCP, the resistor R7, the collector emitter of the transistor Q, and the light emitting diode LED, and the trunk line L2 forms a loop. Even if the terminals (a) and (b) of 5) are in an off (hawk-on) state, the demister SCR remains turned on so that there is no abnormality in the line loop state. Therefore, the light emitting diode LED is turned on continuously to indicate that it is in the air, and at the same time, the melody integrated circuit 6 is "on" so that the melody is provided to the other party through the trunk line L2. That is, when the melody integrated circuit 6 is "on" by the voltage signal output from the emitter terminal of the transistor Q, the output melody is output from the output line MOUT of the melody integrated circuit 6 to the trunk line L2.

(At this time, L2 of the trunk lines L1 and L2 in FIG. 2 is set to ground, but the melody is not connected directly to the ground (GND: Earth) of the exchanger but is cut off by the transformer of the subscriber circuit in the exchanger. In addition, in the standby state as described above, the mute terminal 7 inputs a high voltage to the mute terminal of the communication circuit so that no sound is heard by the receiver, and the mute is operated. This raises the potential at point C.

Therefore, even if the capacitor C3 drops close to zero volts as shown in the third (e) diagram 33, the transistor Q is ensured to be switched by the bias voltage by the resistor R8. This is because the call circuit 4 may be regarded as an equivalent resistance at the time of the call, and the resistance is dropped by the mute line 7 so that the voltage is increased. Here, when the user wants to talk again, that is, when the hand cell is heard at time t2 of FIG. 3, the hook switch 5 is "on" (hook-off), so that the call circuit 4 is formed in the loop or hold circuit (distorter). As a result of being connected in parallel with the SCR, the resistor R7, the transistor Q, and the light emitting diode LED, the hold voltage (point C voltage) drops instantaneously.

Therefore, the voltage at the point (A) input to the non-inverting terminal of the operational amplifier OPA drops rapidly at time t2 as shown in the third (a), and the voltage dropped during the time t2-t3 when the charge of the capacitor C2 is discharged to a predetermined level. Appears. At this time, the capacitor C2 connected to the point (B) of FIG. 2 discharges the voltage charged to the capacitor C2 through the resistor R6 due to the sudden voltage drop at the point C. FIG. 3 (b) shows the waveform. .

Therefore, between the times t2 and t3, the discharge voltage of the capacitor C2 of the third (b) degree becomes greater than the voltage of the third (a) degree, so that the output of the operational amplifier OPA is "high" to "low" as shown in the third (d). When the charge voltage of the capacitor C3 is discharged to the negative voltage level as shown in FIG. 3 (e), the transistor Q which inputs the bias voltage by the resistor R8 is turned off. The instantaneous off-switching of the transistor Q (interval of time t2 t3 in FIG. 3) interrupts the current loop of the thyristor SCR, that is, the cathode and the trunk line L2, so that the thyristor SCR is "off" and the light emitting diode LED is disturbed. The melody integrated circuit 6 also stops working.

The hold loop is therefore released (released). At this time, if the capacitor C3 is not present, there is no transient discharge caused by the "low" output of the operational amplifier OPA, so that the transistor is not "off" and the hold current (loop current) of the demister SCR is not broken, so that the resistor R8 And continue to flow through R9 (the output impedance is " 0 " (zero) when the output of the operational amplifier OPA is low) so that the thyristor SCR is not " off ".

Therefore, the hold loop is released by the discharge of the capacitor C3 at the time when the hand cell is lifted as shown in FIG. 3 (c) at the time t2 of FIG. 3, and the normal call can be made through the communication circuit 3). On the other hand, diode D1 is for preventing the charging voltage of the smoothing capacitor C4 from flowing backward.

In the above case, the case of hold and release of the same telephone is explained. However, when multiple telephones are connected in parallel to one trunk line, the telephone is to be held in one telephone and then the call is made to another telephone connected in parallel with the held telephone. In the same manner as described above, the call circuit in another telephone connected in parallel with the hand cell is turned on at the same time (when the caller wants to talk to another telephone) in parallel with the hold control circuit 3 of FIG. The hold circuit of the held telephone is released.

As described above, the present invention can be refurbished at any time by holding the hand cell without breaking the loop even when the user pushes the hold switch once by pressing the hold switch once when the user wants the standby state. In case of using multiple phones on the same trunk line, there is no inconvenience to wait for the caller to put down the hand cell until the caller starts the call, and there is an advantage that the user can make a call without any problem.

Claims (2)

A telephone capable of switching a standby state, comprising: a hold switching circuit (1) in which a gate of a hold switch (10) and a demister (SCR) are connected in series and the circuit is connected in parallel with a hook switch (5); A line sensing circuit (2) comprising an operational amplifier (OPA) for outputting a logic state opposite to the on state and the off state of the demister (SCR), and on in accordance with the output logic state of the operational amplifier (OPA). A hold control circuit (3) which performs an off operation and a display operation is provided to form a hold loop by a single pressing of the hold switch (10), and the hold loop is turned on by the on state of the hook switch (5). Automatic hold release circuit of a telephone, characterized in that released. The circuit of claim 1, wherein the line sensing circuit (2) is a comparison circuit composed of an operational amplifier (OPA), which uses a trunk line voltage as a power source, the non-inverting terminal and the inverting terminal are composed of a divider circuit, and the capacitor C2 is connected to the inverting terminal. A circuit characterized in that it is connected to output a logic state inverted at the same time as the hook switch (5) is turned on.