KR810002109B1 - Communication interface circuit - Google Patents

Abstract

The cct. for use in a tele-typewriter, the remote transmitter-receiver devices of the CRT terminal and the TELEX, is composed of the transmitter and the receiver ccts. The transmitter cct. comprises the control ccts(1)(2) connected to the transmit terminal(+). The ccts(1)(2) are composed of the photo-couplers(PC1)(PC2), the capacitors(C1)(C2), the resistors (R1,R2)(R3), the transistors(Q1,Q2)(Q3,Q4) and the diodes (D1)(D2). The receiver cct. comprises the reverse voltage protection cct., the current sensing cct., and the temp. compensating cct.

Description

Communication connection circuit

1 is a system diagram of a transmission unit among communication connections.

2 is a system diagram of a receiver of a communication connection.

3 is a transmission subcircuit diagram.

4 is a circuit diagram of a receiver.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a communication interface (C0mmunication Interface) circuit used in a telegraph type-transmitter, a remote transceiver of a CRT (CATHODE RAY TUBE) terminal, and a transceiver of a telex.

The communication connector of the telegraph typewriter, the CRT terminal and the telex transmitter and receiver used in the past have used a mechanical relay to connect the line with the excitation coil of the relay to operate the contacts.

There were three problems with this:

The first is the current flowing in the line, which excites the excitation coil of the relay, resulting in an inductive load.

The characteristics of this load change the resistance depending on the frequency of the interrupted current, so the ups and downs of the current shorten the lifespan of the relay.

To solve this, the line load and source elements had to be designed to be pure resistive loads,

Second, polar relay is used for polarity operation, and it operates at high speed due to the occurrence of false information due to residual operation (chartering) at the contact (amateur) that changes the polarity and slow movement speed of the contact. I couldn't,

Third, the communication connection part operating as a mechanical relay, if the noise or impact amplitude enters the line during the operation of the relay with the receiving function, the relay is operated, resulting in the misinformation.

That is, new problems for controlling the noise and controlling the operating current of the relay have emerged.

The present invention is to solve such problems as described below according to the accompanying drawings.

1 is a system diagram of a transmitter.

In general, in case of long distance transmission, high voltage (ex: 60V or 130V) should be applied to external line to make current flowing through it constant.

The high voltage through which a constant current flows in the power supply is shown at 1 of the power selection switch S ₁ .

The power selection switch S ₁ should be switched to 1 if the method of applying power to the loop of the line is applied from the local station and to 2 if power is applied from the opposite pole.

If the power selection switch S ₁ is set to 1, the power is applied to the control circuits 1 and 3. The operation of the control circuit is as follows.

The input signal is divided into control signals A and B through logic circuits, respectively, and control signal A is applied to control circuit 2 through control circuit 3 and control circuit B is applied to control circuit 1 through control circuit 4. .

In the end, the same circuit operates in the diagonal direction, and the engagement point is connected to the transmitting terminals C and D to become an external line.

Position 1 of the current selection switch S ₂ is used for polar operation, and position 2 is used for neutral operation.

For example, the polar operating station power method is described as follows.

When the input signal is low, the control signal A becomes high, so that the control circuit 3 is turned on and the control signal B is turned low to turn off the control circuit 4-1.

Eventually, the current of the power supply flows from the transmission terminal D to C through the control circuit 3 and enters the power supply through the control circuit 2.

Therefore, current flows from terminal D to C in the transmission line.

When the next input signal is high, the control signal A goes low and the control circuits 3 and 2 are turned off. The control signal B becomes high and the control circuits 4 and 1 are turned on. Flows from line D back through the control circuit back to the power supply. That is, since the direction of the current is changed in the transmission terminals C and D according to the state of the input signal low or high, polarity operation is possible. In the case of neutral operation, the current selection switch (S ₂ ) is set to 2 and the control signal B goes low regardless of the input signal, so that the control circuits 1 and 4 are turned off, so only the control circuits 3 and 2 are turned on or off according to the input signal. In this state, the current directions at the transmission terminals C and D are determined. When power is applied to the track from the other station, nationality cannot be operated in its own country and only neutral operation is possible.

In this case, the power selection switch S ₁ is switched to 2 so that the current is supplied through the transmission terminals C and D. In this case, since it cannot be used during polarity operation, the power selection switch (S ₂ ) should be placed in the neutral position ( ₂ of switch S 2). If the current selector switch S ₂ is located at 2, the control circuits 1 and 4 are turned off so that no current flows, and current flows through the control circuits 2 and 3. Therefore, the control circuits 2 and 3 are turned on and off according to the high and low of the control signal A by the input signal, and the transmission operation can be performed by interrupting the current loop supplied from the transmission terminals C and D.

2 is a schematic diagram of a receiver.

Since the current coming into the receiving terminal is a high voltage and current, it must be converted into a voltage used as a transistor transistor logic (TTL) device. It is a level converter and applies its output to the comparator.

The necessity of this comparator is to allow monitoring between the transmitting and receiving lines and to know when there is an abnormality in the line and when the power supply voltage and current on the transmitting side change.

Its function is as a comparison voltage generator. When the reception voltage is set higher than the voltage applied to the comparator, the output signal can be obtained according to the reception signal, but the reception voltage is compared when the impedance between the transmission and reception terminals is increased or the current at the transmitter is decreased. Since it is lower than the voltage, an output signal cannot be obtained, so an abnormal phenomenon can be seen.

3 is a detailed circuit diagram of the transmitter, and its operation is as follows.

First, the polarity operation of the local power supply system will be described.

Switch S ₁ to 1 because of its own power supply and switch S ₂ to 1 because of polarity operation.

When the input signal is low, the output of the inverter (I ₂ ) is low, so that the light emitting diodes of the photocouplers (PC ₂ ) and (PC ₃ ) emit light, and the power selection switch (S ₁ ), the diode (D ₃ ), and the resistor ( The collector voltage across the collector of photocoupler PC ₃ through R ₅ ) is kept low.

At the same time, the collector voltage across the collector of photocoupler PC ₂ is also kept low. Since the collector voltage flows through the photo transistor of the photocoupler PC ₃ , the transistor Q ₅ is cut off and is not operated, so the transistor Q ₆ is also turned off. (Transistor Q ₄ is also turned off.) In other words, photocoupler PC ₂ and PC ₃ are turned on so that transistors Q ₃ and Q ₅ are turned off. At this time, the direction of current is from power supply (+) → switch S ₁ 1 → D ₃ → PC ₃ → external line D (-) → external line C (+) → D ₂ → PC ₂ → power supply (-) Becomes

In addition, since the output of the inverter I ₃ becomes high, the light emitting diodes of the photocouplers PC ₄ and PC ₁ do not emit light, and the phototransistors of the photocoupler PC ₁ are turned off so that the diode D ₁ and the resistors are turned off. The voltage through (R ₂ ) is high on the collector.

This voltage is kept on because it conducts transistors Q ₁ and Q ₂ . (The operations of photocoupler PC ₄ , transistors Q ₇ , and Q ₈ are also the same) In other words, photocoupler PC ₁ and PC ₄ are turned off so that transistors Q ₁ and Q ₇ ) is on. At this time, the current direction is from power supply (+) to switch S ₁ 1 → D ₁ → Q ₂ → external line C (+) → external line D (–) → D ₄ → Q ₈ → power supply (-) Becomes That is, when the input signal is low, the transistors Q ₂ and Q ₈ are turned on and the transistors Q ₆ and Q ₄ are turned off, so that current flows from the C to the D direction at the transmitting terminal.

On the contrary, when the input signal is high, the output of the inverter I ₂ becomes high and the output of the inverter I ₃ becomes low, so that the transistors Q ₂ and Q ₈ are turned off and the transistors Q ₆ and Q ₄ ) is on and current flows from D to C at the transmitting terminal.

In this way, each time the input signal changes, the current at the transmission terminal changes. When you try to operate the trailing be switched to the current select switch (S ₂₎ 2. That is, since the output of the inverter I ₂ is fixed to low regardless of the input signal, the photocouplers PC ₃ and PC ₂ are turned on (the phototransistor is in a conductive state), so that the transistors Q ₆ and Q ₄ ) is fixed in the off state, only the photo coupler (PC ₁ ) and (PC ₄ ) is turned on / off according to the input signal.

In other words, when the input signal is low, the output of the inverter I ₃ becomes high so that the photocouplers PC ₁ and PC ₃ are turned off, so the transistors Q ₂ and Q ₈ are turned on and the current of the power supply is turned on. Flows through the diode D ₁ and the transistor Q ₂ from the transmission terminal C to D (external line) and flows through the diode D ₄ and the transistor Q ₈ .

When the input signal is high, the output of the inverter I ₃ becomes low and the photocouplers PC ₁ and PC ₄ are turned on so that the transistors Q ₂ and Q ₈ are turned off, and the transistor Q ₆ ) And (Q ₄ ) are off (switch S ₂ ) is connected to two points, so the output of inverter I ₂ is always low. No current flows in any of the transmission terminals C and D. .

In other words, when the input signal is low, current flows from the transmission terminal C to D. When the input signal is high, no current flows. When the transistors Q ₁ , Q ₃ , Q ₅ , and Q ₇ are turned off, the base impedances of the transistors Q ₂ , Q ₄ , Q ₆ , and Q ₈ become high and oscillate Mount capacitors (C ₁ ), (C ₂ ), (C ₃ ) and (C ₄ ).

Diodes (D ₁ ), (D ₂ ), (D ₃ ) and (D ₄ ) are connected to the power selector switch (S ₁ ) at two points (when external power is supplied to the line from the other station, This is to prevent reverse current.

4 is a detailed circuit diagram of the receiver and its operation is as follows.

The current flowing through the receiving terminal is connected to the receiving terminal through an external line at the transmitting terminal of the transmitter, and emits the light emitting diode of the photocoupler PC ₅ through the diode D ₅ and the resistor R ₉ and emits the diode D _7. Flows through). When the light emitting diode of the photocoupler PC ₅ emits light, the voltage of the K point changes as a current flows through the collector of the photo transistor and the variable resistor VR ₁ is varied.

In addition, if the variable resistor VR ₂ is adjusted so that the current flowing through the resistor R ₉ and the light emitting diode of the photocoupler PC ₆ are the same, the current flows through the photocoupler PC ₆ collector and the variable resistor ( By varying VR3), the voltage at point L is obtained.

This voltage is referred to as the reference voltage and the variable resistor VR ₃ is adjusted to 1.5V (as a comparator), and the voltage at the point K is the current to cut off from the current flowing through the receiving terminal (e.g. Adjust the variable resistor (VR1) to 1.5V at 20mA operation.

K. The procedure for equalizing the voltage at L point is as follows.

First: Adjust the variable resistor (VR1) to match the hysteretic characteristics of the comparator at the reference value of the initial receive current (e.g., 10mA for 20% final operation, ie, 2/1 of the operating current as the reference value).

Second: Adjust the resistance value of the variable resistor VR3 to be the same as the resistance value of the variable resistor VR1.

Third: Adjust the resistance value of the variable resistor VR2 such that the voltage at the L point is equal to the voltage at the K point determined by the variable resistor VR1 at the reference value of the minimum received current.

This adjustment can change the point at which the reception current is cut off by adjusting the variable resistance VR3 by controlling the sensitivity of the receiver, so that it is easy to know whether there is an abnormality in tapping and line.

In addition, the photocouplers PC ₅ and PC ₆ have the same characteristics as the current flowing through the resistor R ₉ since the voltage at the points K and L changes according to the ambient temperature, thereby changing the reception sensitivity (receive cut-off current). The photocoupler PC ₆ adjusts the farewell resistor VR ₂ so that the photocoupler PC ₆ flows to the light emitting diode to keep the differentiation of the K point and the L point according to the temperature constant.

In other words, since the temperature sensitive photocoupler PC ₅ and PC ₆ are the same element and the variable resistors VR ₁ and VR ₃ connected thereto are adjusted to the same resistance value, the current sensing circuit R ₉ , PC ₅ , VR ₁ ) and the temperature compensation circuit (R ₁₀ , VR ₂ , PC ₆ , VR ₃ ) become the same condition. Therefore, when the temperature changes, the reference voltage is changed under the same conditions to compensate for the temperature.

Therefore, when the current drawn from the receiving terminal flows through the diode (D ₅ ), resistor (R ₉ ), photocoupler (PC ₅ ), diode (D ₇ ), depending on the brightness of the diode light of photocoupler (PC ₅ ) The voltage at the K point changes and is introduced into the comparator. The voltage is compared with the L positive voltage, which is the reference voltage, in the comparator. The voltage is high when the reference voltage is higher than the reference voltage and low when the reference voltage is low. The brightness of the diode light of the photocoupler PC ₅ is proportional to the current of the receiving input terminal, and the voltage at the K point is proportional to the brightness of the diode light of the photocoupler PC ₅ .

As described above, when using a conventional mechanical relay or a polar relay, the above-mentioned defects are completely based on the communication connection circuit of the present invention, which is susceptible to vibration or ambient temperature and has often been malfunctioned due to noise on the line. In particular, the reference voltage can be adjusted at the receiver to prevent malfunctions against external noise, to detect slight abnormalities on wiretaps and lines, and to make large devices electronic and small devices. .

Claims (1)

As described in the text and illustrated in the drawings, in a full-body typewriter having polarity operation and neutral operation, a remote transceiver of a CRT (Catode Ray Tube) terminal, and a transceiver of a telex, a photocoupler (PC ₁ ) and a capacitor ( C ₁ ), resistors (R ₁ , R ₂ ), transistors (Q ₁ , Q ₂ ), diode (D ₁ ) is a control circuit (1), photocoupler (PC ₂ ), condenser (C ₂ ) consisting of , The control circuit 2 configured by connecting the resistor R ₃ , the transistors Q ₃ , Q ₄ , and the diode D ₂ to the transmission terminal (+) and correspondingly configured control circuit 3 And a transmitter circuit configured to connect the control circuit (4) to the transmission terminal (-) so that the control circuits (1), (2), (3) and (4) are bridge circuits, a diode (D ₆ ), and a resistor ( R ₈ ), zener diodes (ZD ₁ , ZD ₂ ), reverse voltage protection circuit composed of diode (D ₈ ) interconnected, diode (D ₅ , D ₇ ), resistor (R ₉ ), photocoupler (PC ₅₎ ), a variable resistance (VR ₁₎ And mutually connected configured current-sensing circuit, a resistor (R _10), variable resistor (VR _2, VR _3), photo coupler is (PC ₆₎ the interconnection is connected consisting of a temperature compensation circuit is a comparator with each other characterized by a configured receiver circuit Communication connection circuit.

Images