| 摘要 |
PURPOSE:To facilitate grasp of a fault by allowing a center to monitor a video signal at an optional position of a transmission line. CONSTITUTION:A center equipment A is provided with a channel designation means X1 designating an outgoing channel to be monitored, a position designation means X2 designating a monitored position, a control data transmission means X3 modulating channel identification data and address data and sending the result to a control channel, and a video display means X4 receiving a video signal from the monitored channel and displaying visually the video image. Moreover, each of video signal return devices B1-Bn has a demodulation means Y1 demodulating channel identification data and address data from an outgoing control channel, an address discrimination means Y2 discriminating whether or not its own equipment is designated, a selection means Y3 extracting the video signal of the outgoing channel corresponding to the channel identification data from a transmission line E through branching, and a monitor video image transmission means Y4 frequency-converting the video signal to a signal of an incoming monitor channel and sending the converted signal to the transmission line. |
