KR100232725B1 - Loop dialing circuit in key-phone system - Google Patents

Abstract

The present invention relates to a loop dialing circuit in a key phone system that can expect an improvement effect such as cost and noise by implementing a loop dialing circuit without using a relay when a dial pulse is generated. An overvoltage protection circuit unit for protecting an internal circuit, a bridge diode installed in consideration of the directionality of current, a photocoupler for interrupting a DC voltage applied from the outside by performing an on / off operation based on a predetermined control signal. DC loop circuit to form a DC loop based on the DC voltage applied from the outside by the intermittent operation of the photocoupler, and a matching transformer for impedance matching between the main device and the key-phone telephone.

Description

Loop dialing circuit in key phone system

The present invention relates to a key phone system, and in particular, by implementing a loop dialing circuit without using a relay generally used to generate a dial pulse, a key phone system which can expect an improvement effect such as cost and noise. Relates to a loop dialing circuit.

Currently, in order to generate a dial pulse in a telephone, it is generally possible by interrupting the DC power of a loop connected to the other side. In this case, a relay is used as an element used to control the loop power.

The relay is composed of a switch and a predetermined interrupting means for controlling the switch. When a high level or low level signal is received from a predetermined control source capable of outputting a high level or low level signal, The intermittent means supplies the DC power by mechanically shorting the switch or by opening the switch to cut off the DC power to supply the dial pulse.

However, as described above, the relay used to interrupt the DC power source can be easily understood that the noise is generated as the switch repeats the intermittent operation because the implementation method uses a mechanical switch. .

In addition, there is a disadvantage that the size is increased according to the implementation of the relay by having a mechanical switch.

Accordingly, the present invention has been made in view of the above circumstances, and implements a loop dialing circuit using a photo-coupler without using a relay when generating a dial pulse, thereby improving cost and noise. The objective is to provide a loop dialing circuit in a expected key phone system.

1 is a block diagram illustrating the concept of a loop dialing circuit in a key phone system according to an embodiment of the present invention.

2 is a detailed circuit diagram of FIG.

* Explanation of symbols for main parts of the drawings

10: bridge diode 20: loop control circuit

30: matching transformer 40: photo coupler

V: Varistor D: Bridge Diode

R1 to R4: Resistor Q1: Transistor

Q2: field effect transistor C: capacitor

In the key phone system according to the present invention for realizing the above object, the loop dialing circuit includes an overvoltage protection circuit unit for protecting an internal circuit from an overvoltage introduced from the outside, a bridge diode installed in consideration of the directionality of a current, and a predetermined control signal. A photocoupler for intermitting a DC voltage applied from the outside by performing an on / off operation based on a DC, and a DC loop that is on / off according to the intermittent operation of the photocoupler to form a DC loop based on a DC voltage applied from the outside And a matching transformer for impedance matching between the loop circuit and the main device and the key-phone telephone.

That is, according to the above, it is possible to generate the dial pulse without using a relay which is conventionally used to generate the dial pulse, thereby reducing the cost, improving the noise, and reducing the circuit implementation size. .

Next, an embodiment according to the present invention will be described.

1 is a block diagram illustrating the concept of a loop dialing circuit in a key phone system according to the present invention.

In the drawing, reference numeral 10 denotes an overvoltage protection circuit unit implemented using a bridge diode installed in consideration of the direction of current and a varistor installed to protect an internal circuit against an overvoltage input from a power station. Loop dialing circuit implemented using photocoupler, transistor, field effect transistor, etc., 30 is for impedance matching between main device (not shown) and internal circuit, and for converting input signal from main device into signal level suitable for key-phone telephone Impedance matching transformer.

That is, according to the above configuration, the DC power supply of -24V supplied from the main device through the tip wire (TIP) and the ring wire (RING) is connected to the key phone telephone via the bridge diode and the overvoltage protection circuit part 10, and this DC loop Will remain open under normal conditions.

At this time, when a predetermined control signal is received from a processor (not shown) as a control unit for controlling the overall apparatus of the key-phone telephone, the loop control circuit 20 supplies a -24V DC power supplied from the main device with the magnetic power cut off. By repeating the intermittent operation for, the dial pulse is generated.

On the other hand, the voice signal is introduced into the key phone telephone through the matching transformer 30 via the loop control circuit 20.

2 is a circuit diagram showing in detail the loop dialing circuit in the key phone system according to the present invention according to FIG.

In the figure, reference numeral 30 denotes an impedance matching transformer for impedance matching between the main unit and an internal circuit and converts an input signal from the main unit into a signal level suitable for a keyphone telephone, and 40 denotes a photocoupler, a keyphone telephone processor (not shown). For example, when a low level signal is received, the internal transistor is turned on (Turn_On) by light emission of the internal diode.

Reference numeral V denotes an overvoltage protection circuit installed using a varistor to protect the internal circuit when an overvoltage is input from the outside, and D denotes a bridge diode installed in consideration of the direction of the current, and R1 to R4 denote resistance and Q1. The silver transistor, Q2 is a field effect transistor, and C is a DC block capacitor for cutting off the DC power supplied from the main device.

Next, the operation of the device having the above configuration will be described.

First, the varistor V and the bridge diode D monitor the DC power of -24V supplied from the tip wire and the ring wire connected to the main device to suit the internal circuit of the key phone telephone. Then, the closed loop formed by a series of circuits of the tip line, the ring line, and the key-phone telephone, for example, the tip line transistor Q1, the field effect transistor Q2, the resistor R3, the ring line is in a normal state (for example, in a non-call state). ) Will remain open.

That is, since the control signal applied to the photocoupler 40 from the key-phone telephone processor in the normal state maintains a high level signal, the photocoupler 40 included in the DC loop becomes inoperative of the internal light emitting diode. The transistor is turned off, so that the transistor Q1 and the field effect transistor Q2 are also turned off so that the loop is kept open.

At this time, when a low level signal is applied to the photocoupler 40 from the key-phone telephone processor, the light emitting diode inside the photocoupler 40 operates as a predetermined light source. In this case, an internal transistor of the photocoupler 40 is used. Will be turned on.

Subsequently, as the internal transistor is turned on, a potential difference of a predetermined level or more occurs between the emitter terminal and the base terminal of the transistor Q1, and the transistor Q1 is turned on.

As the internal transistor is turned on, the current that is energized is applied to the gate terminal of the subsequent field effect transistor Q2, and thus the field effect transistor Q2 is also turned on.

Thus, since the power applied from the tip line is a DC component, it is cut off from the DC block capacitor C, so that a closed loop as described above forms a DC loop. When the level of the control signal applied from the key phone telephone processor to the photocoupler 40 is switched to the low level, the DC loop is opened. As described above, the DC loop generates a dial pulse while repeating the short circuit and the open circuit based on the control signal of the processor.

Thereafter, when the transistor Q1 is saturated, the AC component of the voice signal passes through the DC block capacitor C and enters the matching transformer 30, so that the voice signal is input to the internal circuit.

That is, according to the above embodiment, it is possible to generate the dial pulse without using the relay which is conventionally used to generate the dial pulse, so that the effect of reducing the cost, improving the noise and reducing the circuit implementation size can be expected. do.

In addition, this invention is not limited to the said Example, It can variously deform and implement within the range which does not deviate from the technical summary of this invention.

As described above, according to the present invention, by implementing a loop dialing circuit without using a relay commonly used to generate a dial pulse, a keyphone system capable of improving cost and noise can be expected. The loop dialing circuit can be realized.

Claims (1)

An overvoltage protection circuit portion provided between the tip wire and the ring wire to protect the internal circuit from the overvoltage introduced from the outside, a bridge diode installed in consideration of the directionality of the current between the tip wire and the ring wire, and on / off operation based on a predetermined control signal. A photocoupler for intermitting a DC voltage applied from the outside and a transistor turned on / off according to the intermittent operation of the photocoupler between the tip line and the ring line to form a DC loop, and according to whether the DC loop is formed In a key phone system comprising a DC loop circuit for generating a predetermined dial pulse, and a matching transformer for impedance matching between the main device and the key phone telephone, as well as transmitting the dial pulse generated and applied in the loop circuit. Loop dialing circuit.