DIGITAL COMMUNICATION DEVICE

摘要

PURPOSE:To enable transmission of high quality supervisory and control information economically without giving influences on main signal information transmission characteristic eliminating necessity of providing a separate transmission line for information transmission by inserting a small number of auxiliary codes in a series of digital signals of a main signal to be transmitted and amplitude modulating the auxiliary codes by a supervisory control signal. CONSTITUTION:The transmitting device detects the auxiliary code from the output signal of a transmission code converting circuit 3 by a block synchronizing circuit 12, and amplitude modulates the auxiliary code by an AND gate 13, a differential amplifier 16 and a gate circuit 18 according to the supervisory control signal of a terminal 2. The receiving device takes difference between an output 41 of a discriminator 36 and an output 39 of a waveform equalizer 34 by a differential circuit 42, rectifies the output by a full wave rectifier circuit, and takes out the supervisory control signal to a terminal 47 by a low pass filter 46.