KR920004148B1 - Holding automatic releasing circuit and method - Google Patents

Abstract

The auto hold releasing circuit protects the hold call from the instantaneous line voltage variation and releases the call only when the hand set of a telephone connected to the call holding telephone in parallel. The circuit includes a hold switch (SW11) for generating hold instruction, a line voltage checker connected between the lines (L1,L2) for connecting a path controller and a communication circuit (22), a CPU (20) for holding the current path according to the hold insturction and for generating hold control signal to release the hold when line voltage decreases constantly during a fixed time, and a diode (D11) for providing path for transmitting the hold control signal to the path controller (23).

Description

Horde automatic release method and circuit

1 is a conventional circuit diagram.

2 is a circuit diagram of the present invention.

3 is a flow chart of the present invention.

* Explanation of symbols for main parts of the drawings

20: CPU 21: bridge rectifier

22: call circuit 23: call path control unit

25: power supply R11-R17: resistance

Q11-Q13: Transistor C11: Capacitor

SW11: Holder Bolt SW12: Hook Switch

D11-D-13: Diode CH11: Choke Coil

The present invention relates to a telephone having a hold function, when an arbitrary telephone calls an incoming / outgoing call and then extorts the called call from another telephone connected in parallel with the arbitrary telephone. A method and circuit for automatically releasing a called call.

In general, a telephone refers to a terminal device that is connected through a public telephone communication network to provide a voice call service between subscribers.

When multiple telephones are connected in parallel to one telephone network, telephones equipped with the call function are called when a user enters a call command to transfer a call established by an incoming / outgoing call to any other paralleled telephone. Old.

And when any other telephone connected in parallel extracts the old call, the telephone that called the call must release the old call.

In the conventional case, a call that has not been automatically released cannot be released by a user's release command input or a call that has been called by a silicon controlled rectifier (hereinafter referred to as SCR). Recovered. The old automatic release circuit using the SCR is configured as shown in Figure 1 and the operation will be described below.

The first automatic release circuit is connected between the bridge rectifier (not shown) and the communication path controller 11, and when the user presses the old button SW1 in a call state, the SCR 10 is turned on. A call loop is formed through line L1-> SCR 10-> resistance R1-> line L2. At this time, the capacitor C1 is charged with the voltage divided by the resistor R1. The resistor R2 and the capacitor C2 are connected with an appropriate time constant for the stable tun ON state of the SCR 10.

At this time, when the handset is lifted by another telephone connected in parallel, the voltage on the line L1 is instantaneously lowered by the other telephone. Therefore, the voltage charged in the capacitor C1 is momentarily higher than the voltage on the line L1, so that the SCR 10 is turned off (tun off) so that the call loop is blocked. Therefore, the called call is released.

However, the call automatic release circuit as shown in FIG. 1 is used when the voltage on the call path from the public telephone network to the calling phone is changed instantaneously without the handset of another telephone connected in parallel. There was a problem that the call being released is automatically released due to the voltage change.

It is therefore an object of the present invention to protect a hoarded call in a telephone from the effects of instantaneous voltage changes on a line and to automatically release a honed call when the handset of a paralleled telephone is heard. An automatic release method and a circuit are provided.

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

2 is a circuit diagram of the present invention, which is connected between a bridge rectifier 21 connected to a tip of a telephone line and a ring terminal, a communication circuit 22, and a bridge rectifier 21 and the communication circuit 22. A telephone having a call path control unit 23 for forming and releasing a call path, comprising: a call and switch SW11 for generating a call command signal by switching, the call path control unit 23 and a call circuit ( 22 is connected between both connection lines L1 and L2 to detect a voltage change between the two connection lines L1 and L2, and the choke coil CH11 and the capacitor C11 and the diode D12 and two A voltage monitoring means consisting of resistors R11 and R12, and a call path formed in response to a call command signal of the old switch SW11 in a call path formation state and a predetermined time set by the voltage monitoring means. As the voltage drop maintained during A central processor unit (hereinafter referred to as a CPU) 20 for generating a call control signal for releasing an existing call path, and is connected between the voltage monitoring means and the CPU 20 and the voltage; In order to relay the output of the monitoring means, it consists of a relay means consisting of two resistors R13 and R14, a diode D13, a transistor Q11 and a power supply unit 25.

3 is a flow chart of the present invention, which includes a first process of calling up the formed call path for input of a call command in the state where a call path is formed, and whether the voltage on the call path drops after performing the first step. A second step of checking; and a third step of checking whether the voltage drop state is maintained for a predetermined time when the voltage on the communication path increases in the second step; and the voltage on the call path in the third step. If the enhanced state is maintained for a certain time is made a fourth process of releasing the arc.

Hereinafter, the operation according to the present invention will be described in detail with reference to FIGS. 2 and 3.

The bridge rectifier 21 and the call circuit 22 during the second period have the same function and operation as the conventional phone configuration, and thus detailed description thereof will be omitted.

The hook switch SW12 of the call path controller 23 is turned on when hook-off, that is, when the user hears the handset.

At this time, the two transistors Q12 and Q13 are both turned on to form a communication path consisting of the line L1-> the call circuit 22-> the line L2.

In the state in which the hook switch SW12 and the two transistors Q12 and Q13 are turned on to form a communication path, the CPU 20 is configured as a user presses the old button SW11 in step 30 of FIG. Check if the old command signal is input. When the old command signal is input in step (30), the CPU 20 activates and outputs the old control signal to the "high" logic state through the output port A in step (31). Accordingly, the call control signal in the "high" logic state is applied to the base terminal of the transistor Q13 of the communication path controller 23 through the diode D11, so that the call path formed even when the hook switch SW12 is turned off. To keep it going.

Meanwhile, the voltage monitoring means including the choke coil CH11, the diode D12, the capacitor C11, and the two resistors R11 and R12 in the state in which the communication path is formed is connected to the communication path controller 23 and the communication circuit 22. The switch between both connection lines L1 and L2 is monitored and a state in which the potential difference is changed is applied to the input port B of the CPU 20 through the relay means.

In addition, the relay means composed of a diode D13, a power supply unit 25, a transistor Q11, and two resistors R13 and R14 changes the output of the voltage monitoring means to level the input port B of the CPU 20. Will be sent to.

The operation of the voltage monitoring means and the relay means will be described in detail as follows.

In the state in which the communication path is formed, the voltage on the line L1 is supplied to the power supply unit 25 through the choke coil CH11 and the diode D13, while the resistor R11? Diode D12 via the choke coil CH11. ? Is supplied to the base terminal of transistor Q11 through resistor R13.

At this time, the capacitor C11 is charged by the voltage dropped by the resistor R11.

The resistance values of the two resistors R12 and R13 are set to about tens of kiloohms (KΩ) so as to have an appropriate value with respect to the resistance value of the resistor R11 and not to affect the power supply unit 25.

Transistor Q11 operates in the saturation region and is turned on by the voltage on the line L1 applied to the base terminal to be divided to the operating voltage input from the power supply unit 25 to the collector terminal through the resistor R14. Mutes to line L2. Therefore, the voltage sensing logic signal of the "low" logic state is transmitted to the input port B of the CPU 20. The resistance value of the resistor R14 is set to allow the transistor Q11 to flow the amount of current required to operate in the saturation region.

The voltage on the line L1 is lowered when the handset of another telephone connected in parallel is heard while the voltage sensing logic signal of the "low" logic state is supplied to the input port B of the CPU 20. At this time, due to the voltage drop on the line L1, the capacitor C11 discharges the charged amount of charge through the resistor R11, and the negative terminal (-) of the capacitor C11 is relatively grounded. In this case, the transistor Q11 is turned off because a voltage of the base terminal " Volt " of the transistor Q11 is applied.

In this case, the output voltage of the power supply unit 25 is applied to the input port B of the CPU 20 through the resistor R14.

Therefore, the CPU 20 receives the voltage sensing logic signal of the "high" logic state as the entry port B, and judges that the handset of another telephone connected in parallel is heard. The diode D13 prevents the capacitor C11 from being recharged by the power supply unit 25, and the choke coil CH11 flows into the power supply unit 25 and the capacitor C11 from the line L1. Remove it.

On the other hand, the CPU 20 checks whether the voltage sensing logic signal of the "high" logic state is input to the input port B by the power monitoring means and the relay means in step 32 after performing step (31). Wait until

When the voltage sensing logic signal of the "high" logic state is input in step 32, the CPU 20 proceeds to step 33, and does the voltage sensing logic signal of the "high" logic state last for a predetermined time period? Check it. At this time, if it does not last for a predetermined time, it is determined by the voltage fluctuation on the line instantaneously and returns to the step (32). In this case, the predetermined time is set to 30 ms to prevent the release of the old by a momentary voltage change on the line.

If the voltage sensing logic signal of the "high" logic state is continuously input for a predetermined time or more in step 32, the CPU 20 proceeds to step 34 and outputs through the output port A. The old control signal of the "high" logic state is non-active and output to the "low" logic state. The old control signal in the logic " low " logic state is applied to the base terminal of the transistor Q13 of the control section 23 via the diode D11 to turn off the two transistors Q12 and Q13. This releases the old.

On the other hand, if it is not the input of the old command signal in step (30), the CPU 20 proceeds to step (35) to perform a function for the command.

As described above, the present invention has an advantage of automatically releasing a call that has been released in response to a voltage fluctuation on a call path, and a parallel connection in which voltage fluctuations are generated on a line according to a maintenance period of a voltage fluctuation state on a call path By determining whether the voltage fluctuation caused by listening to the handset of another telephone is prevented, there is an advantage that a malfunction can be prevented during the automatic automatic release operation.

Claims (2)

The bridge rectifier 21 connected to the tip of the telephone line and the ring terminal, the communication circuit 22, and the communication path connected between the bridge rectifier 21 and the communication circuit 22 to form and release a communication path. In the telephone having the control unit 23, a call switch SW11 for generating a call command signal by switching, and both connection lines L1 and L2 between the communication path control unit 23 and the call circuit 22; Voltage monitoring means for detecting a voltage change between the two connection lines L1 and L2, and the formed call path in response to a call command signal of the old switch SW11 in a call path formation state. A central processing unit (20) for generating a call control signal for releasing the call path during the call as the voltage drop is detected and maintained for a predetermined time set by the voltage monitoring means; Old control of 20 Call the call, characterized in that the configuration of a diode (D11) to provide a control path for call transfer to a control unit 23 automatically releases the old circuits. A method for automatically releasing calls to a telephone, the method comprising: a first step of calling up the formed call path by inputting a call command in a state in which a call path is formed; and a voltage on the call path drops after performing the first step. A second step of checking a value; a third step of checking whether the voltage drop state is maintained for a predetermined time when the voltage on the communication path drops in the second step; and the call path in the third step And a fourth step of releasing the horn when the voltage drop state of the phase is maintained for a predetermined time.

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