SU1336258A1 - Device for transmitting and receiving information via matched two-wire communication line - Google Patents

Abstract

This invention relates to telecommunication technology and increases immunity to interference. The device contains information transmitters (PI) 1, each of which contains a composite phototransistor (SFT) 2, a resistor 3, wires 4 and 5 of the communication line, matching resistors 6 and 7, power supply 8, receivers 9 information, each -pump contains a resistor 10 and a radiating diode 11, two matching el-ta (EI) 12, each of which contains a capacitor 13, a transistor 14, a diode 15 and a resistor 16. The introduction of two EO 12 reduces the amplitude of the reflected signals from the ends of the line connection, improves the pulse shape, which reduces the likelihood of the receivers 9 from interference. Performing each PI 1 based on SFT 2, receiver 9 on series-connected resistor 10 and diode 11 allows for complete galvanic. isolation between the units connected to the communication line, which increases the insulation resistance and reduces the magnitude of the parasitic capacitive coupling. All this increases the noise immunity of the device. 1 il. "(L 12 with so O5 GhE O1 c

Description

The invention relates to telecommunications technology and can be used in information transmission systems.

The purpose of the invention is to improve the noise immunity,

The drawing shows a block diagram of a device for transmitting and receiving information over a matched two-wire communication line.

The device contains information transmitters 1, each of which contains a composite phototransistor 2, resistor 3, first 4 and second 5 wires of the communication line, matching resistors 6 and 7, power supply 8, information receivers 9, each of which contains a resistor 10 and a radiating diode 11, two matching elements 12, each of which contains a capacitor 13, a transistor 14, a diode 15 and a resistor 16.

The device works as follows.

In the initial state, the composite photo-transistors 2 of all transmitters 1 are closed, since the radiation energy from an external device (not shown) does not come to their bases. In this case, a corresponding potential difference is established between the first 4 and the second 5 wires, resulting in a current flowing through the emitting diodes 11 of the receivers 9, the value of which is set by resistors 10. Under the influence of the flowing current, the emitting diodes emit energy received by external devices which is the output of device receivers 9. At the same time, the capacitors 13 of the matching elements 12 are charged to the potential difference value of the first 4 and second 5 wires of the communication line, the transistors 14 are closed, the resistors 16 are disconnected from the communication line, in which nothing the energy consumption of the matching elements 12 from the power supply 8.

In the mode of transmitting the information "1, the base of the composite phototransistor 2 of one of the transmitters 1 receives radiation energy from the external device, as a result of which it opens and short-circuits the communication line, while the potential difference between the first 4 and second 5 lines of the communication line decreases, leads to a decrease in the amount of current flowing through the emitting diodes 11 of the receivers 9, and to the cessation by them of the radiation of energy perceived by external devices. In this case, the capacitors 13 of the matching elements 12 are discharged along the circuit: the first wire 4 of the communication line, the open transition of the collector-emitter of the composite phototransistor 2, the triggered transmitter 1, the second wire 5 of the communication line, the resistor 16 and the diode 15, connect the resistor 16 to the line connection.

In the transmission mode of the logical "About, the external device stops the supply of radiation energy to the base of the composite phototranes

five

five

0

0

0

Zistor 2 of the information transmitter 1, as a result of which it closes, and between the wires 4 and 5 of the communication line the potential difference begins to be established, under the influence of which the receivers 9 begin to flow through the radiating disks 11 and they begin to radiate the energy that is the output signal of the receivers 9 In this case, the capacitors 13 of the matching elements 12 begin to be charged by the current flowing through them along the circuit: the first wire 4 of the communication line, the capacitor 13, the base-emitter junction of the transistor 14, the resistor 16 and the second wire 5 of the LINK line. leads to the connection of the resistor 16, equal in magnitude to the wave resistance of the communication line, through an open collector-emitter junction of the composite phototransistor 2 to the communication line, according to the latter. When the capacitor 13 of the matching element 12 is charged, the voltage across it gradually increases to a value equal to the potential difference between the first 4 and second 5 wires, and the charge current flowing through it gradually decreases to a minimum value equal to the last leakage current. transistor 14, through the time required for matching the communication line (process termination), gradually locks in, disconnects the resistor 16 from the communication line. For the conditions of reliable matching of the communication line, the time value of the specifying capacitor 13 of the matching element 12 is determined by the formulas

with.

(i;

(2)

where t ,, is the minimum duration of the information signal; 1f is the pulse front duration; ZB is the characteristic impedance of the link; P is the gain of the transistor matching element.

The condition of formula (1) is fulfilled due to the time required for the complete recharge of the time of the driving capacitor, and the conditions of formula (2) ensure reliable damping of the current wave and voltage at the ends of the communication line.

Claims (1)

Invention Formula A device for transmitting and receiving information on a matched two-wire communication line containing a power source, the positive and negative terminals of which are connected respectively to the first terminals of the matching resistors, the second terminals of which are connected respectively to the first and second wires of the matched two-wire communication line, the information receiver, the first and the second inputs of which are connected to the corresponding wire of the agreed two-wire communication line, the information transmitter, the first and second terminals of which connected to the first and second wires of the matched two-wire communication line, respectively, in order to improve noise immunity, two matching elements are introduced, each of which contains a transistor whose collector is connected to the first capacitor terminal and is the first terminal of the matching element, the base of the transistor connected to the second terminal of the capacitor and the cathode of the diode, the anode of which is connected to the emitter of the transistor and The first pin of the resistor, the second pin of which is the second pin of the matching element, the information transmitter is made on a composite phototransistor whose collector is connected to the first pin of the transmitter, the base is connected to the first pin of the resistor, and the emitter is connected to the second pin of the resistor and the second pin of the transmitter, and each the information receiver contains a radiating diode, the anode of which is the first terminal of the receiver, and the cathode with the first terminal of the resistor, the second terminal of which is the second terminal of the information receiver, the first and second terminals of the matching elements being connected to matched two-wire communication lines.