JPS56102186A - Digital transmission system for subscriber's line - Google Patents

Abstract

PURPOSE:To prevent far-end crosstalk noise by attaching a variable artificial line circuit controlled by the control signal of a f<1/2> AGC circuit to the subscriber's transmitter and attaching also high-frequency breaking circuit to both transmitters on the office and subscriber's sides. CONSTITUTION:A subscriber's binary PCM signal inputted into terminal 172 is code-converted by code converter 222 and then inputted into variable artificial line circuit 23. Circuit 23 which has an attenuation characteristic corresponding to the transmission loss of line 3 between office and subscriber's devices on the basis of f<1/2> AGC control signal 21 of f<1/2> AGC transmission equalization discriminating and reproducing circuit 202 inputs the input signal into high-frequency breaking circuit 242 after adjusting it to the level corresponding to the distance of line 3. Circuit 242 sends a signal, whose frequency components outside the frequency band required for equalization by f<1/2> AGC circuit 20 is suppressed, to the office through time-sharing direction control switch 192. The office makes the sent signal equalize, amplify, discriminate and reproduce in circuit 201 through switch 191 and outputs the processed signal from terminal 181. Thus, all terminating levels from subscriber's terminals, which are located on different distances, to the office are equalized and far-end crosstalk can be prevented.