SU1619416A1 - Double-wire telegraph communication channel - Google Patents

Abstract

The invention relates to electrical engineering and can be used in communication technology to suppress electromagnetic interference in electrical circuits. The aim of the invention is to increase the selectivity. A two-wire telegraph channel contains N series-connected U-shaped low-frequency links consisting of capacitors 1,2,5,6,9,10, chokes 3,4,7 and 8, an RC-chain of resistor 11 and capacitor 12. Increasing the selectivity This is achieved by introducing an RC circuit and choosing the characteristic impedance from the above ratio. 1 il.

Description

The invention relates to wired telecommunications and can be used to suppress electromagnetic interference in electric circuits, namely used in telegraph channels.

The purpose of the invention is to increase the selectivity.

The drawing shows an electrical schematic diagram of an interference suppression filter for telegraph two-wire communication channels containing two U-shaped low-frequency (LF) links in each wire (p-2) (transmitter and receiver are not shown).

 The interference suppression filter for telegraph two-wire channels contains capacitors 1 and 2, chokes 3 and 4, capacitors 5 and 6, chokes 7 and 8, capacitors-9. And 10, a sequential JS-chain consisting of a resistor 1 1 and a capacitor 12. Capacitors 1.5 and 9 and chokes 3 and 7 form one U-shaped two-stage filter, and capacitors 2.6 and 10 and chokes 4 and 8 form the other.

In the radio frequency range from hundredths of MHz to hundreds of MHz, the interference suppression filter for telegraph two-wire channels has a delay band, and in the range from zero to several kHz it has a transmission band in order to ensure the passage of telegraph parcels from a transmitter with output resistance r distortion when the mismatch with the input of the receiver.

The interference suppression filter for telegraph two-wire communication channels operates as follows. When the signal passes through the U-shaped low-frequency links, the RC chain reduces the overvoltage and accelerates the attenuation of voltage oscillations on the output load, since as the output voltage rises, the capacitor 12 is charged through the resistor 11, and Yes, and the subsequent discharge of the capacitor 12, the oscillation energy is dissipated in resistor 11. In order to achieve minimal distortion when transmitting telegraphic parcels, it is necessary to have the same frequency response of the RH receiver as the with an agreed load. To ensure this condition, the elements of a sequential RC-chain must be selected from the following relationship:

R

P-RH

RH-P at the same time

10L t (Vp RH UlnlO X

in addition, the following conditions must be met:

with lo1. about/.

Wc TRi5t (r.un +

where is COP and

t ×

Mox Tr) And-and, accordingly, the frequency

M "ks

R

the slice and the permissible time of establishing a transient at the output of the noise suppression filter for the telegraph two-wire communication channels;

maximum possible output impedance of the transmitter; characteristic impedance of the noise suppression filter for telegraph two-wire communication channels. Since the current through the serial RC-chain flows only during the practical establishment of the transient process, the losses in the resistor 11 are insignificant, they can be neglected. Therefore, the efficiency of the noise suppression filter for the telegraph two-wire communication channels was almost not reduced by the introduction of a serial RC chain.

The advantage of the proposed filter is its versatility, since it can be used in telegraph channels with different values of the output impedance of the transmitter and the input impedance of the receiver of telegraph signals. I

Claims (1)

Invention Formula A telegraph two-wire communication channel consisting of a serially connected transmitter, an interference suppression filter of the communication line and a receiver, while the Interference suppression filter contains in each wire N serially connected U-shaped low-frequency links with a grounded common bus, characterized in that selectivity, parallel to the input of the receiver, a sequential RC-chain is introduced, with the characteristic resistance e161 the noise suppression filter is selected from the ratio , where g is the transmitter output impedance} O is the characteristic impedance of the interference suppression filter; RH is the input impedance of the receiver, and the resistance values of the resistor and capacitor of the series RC circuit are determined from the expressions P PH. Rh-p R ) 6C5 RH .... (J + 1-), inioot gmax RH where is about V Max SOS (RH-p) rMaKc () tRH allowable set time transient filter output; maximum possible output impedance of the transmitter; the angular frequency of the cut-off noise suppressing filter, satisfy, lOlnlOOi