| 摘要 |
PURPOSE:To reduce the deterioration in the transmission characteristic and to prevent the increase in the delay time by providing a transmitter, a receiver, a relay switch and a loopback control circuit to a line coupling section of a loop transmission line, applying non-recovery relay normally and applying loopback via a relay circuit. CONSTITUTION:The relay switches 31, 32 are thrown to the contact (b) by loopback control circuits 51, 52 at each line coupling section LC at normal operation and the relay switches 31, 32 of a station (ST) for data transmission are thrown to the contact (a). In such a state, a data of the station ST sending the data is sent to the next station ST via the relay switches. When the control circuits 51, 52 detect the interruption of the transmission line in charge at loopback, the relay switch 31 (32) is thrown to the contact (c) to form the loopback state. In such a state, the data received in a receiver 12 at the line coupling section at the end is subject to loopback to other transmission line via the switch 32, a recovery relay circuit 42, the switch 31 and a transmitter 21.
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