MONITORING SYSTEM OF DIGITAL RELAY TRANSMISSION LINE

摘要

PURPOSE:To attain the monitoring of a transmission line with high accuracy during in service, by inserting a digital code train having a prescribed code length periodically as a monitoring signal in common for each reproducing relay device, and performing the monitoring control in this period. CONSTITUTION:A monitoring signal having a prescribed period is inserted in a main signal of a code tansmitted from a transmission terminal. This code train transmitted from the transmission terminal is given to an equalizer 3 and a discriminator 4. One output of the discriminator 4 is given to a coupling circuit 25 of a monitor circuit 6 and the other output is given to a monitor signal detection circuit 10 of the circuit 6. A monitor signal is extracted from the code train given to the circuit 10 and a relay device is discriminated in the period of the extracted monitoring signal. In response to the discriminated information, a pulse code is outputted from a voltage controlled oscillator 22 and give to the circuit 25. In the circuit 25, a pulse signal representing the state of a reproducing relay device outputted from the oscillator 12 is inserted to the code train inputted to the circuit 6 and transmitted to the reception terminal. The output frequency of the oscillator 22 is demodulated at the reception terminal and the status of the reproducing relay device is grasped.