| 摘要 |
PROBLEM TO BE SOLVED: To easily grasp a fault in a transmission line by monitoring data communication quality between a center and an optional position of the transmission line at the center. SOLUTION: A center is provided with a center equipment A and data signal return devices B1-Bn are arranged to an optional position of a transmission line E, the center equipment A sends check data, and the data signal return devices B1-Bn, which designate a data signal return device to return the check data, receive the check data returned from the designated data signal return device via an incoming channel, monitor the data communication quality, return the check data sent from the center equipment and received to the center equipment via the incoming channel when the device is designated by the center equipment. |
