BIDIRECTIONAL CATV SYSTEM AND HEAD END, BIDIRECTIONAL RELAY AMPLIFIER, SUBSCRIBER TERMINAL AND TRANSMISSION LINE MONITORING METHOD USED FOR THE SAME

摘要

PROBLEM TO BE SOLVED: To improve the quality of a transmission line by transmitting corresponding address signals and outgoing control signals to a bidirectional relay amplifier by a head end, receiving the signals by the bidirectional relay amplifier, providing an output switch for turning ON/OFF the output of an amplifier for incoming signals and turning ON/OFF the output switch by the outgoing control signals. SOLUTION: Outgoing subscriber data signals from this head end 11 are inputted from a subscriber terminal pull-in line connection terminal 60, sent through a branching filter 61 to a demodulator 70, demodulated to digital data and decoded in a transmission line encoder-decoder 71. An outgoing signal format is composed of bit synchronization and an error correction code and commands are provided with transmission permission, output switch conducting and an incoming quality value request, etc. The bidirectional relay amplifier 13 obtains the bit synchronization by bit synchronizing signals and obtains the synchronization of a frame unit by frame synchronizing signals. When an address specified by the head end 11 matches, a succeeding command is fetched and interpreted.