| 摘要 |
PURPOSE:To prevent the collision of a signal in an overhead earth line by providing a preceding carrier layer to a head of an outgoing signal, providing a reservation carrier layer and a non-carrier layer succeeding thereto to the head of an incoming signal and using the non-carrier layer so as to confirm the presence of the outgoing signal. CONSTITUTION:The outgoing signal has a format where a precedence carrier layer 10 by 20ms exists at its head station 4 and a data layer 11 follows the precedence carrier layer 10. Moreover, the incoming signal has a format where a reserved carrier layer 12 by 15ms exists at its head, the non-carrier layer 13 of 20ms follows the reserved carrier layer 12 and the data layer 14 follows the non-carrier layer 13. In sending the outgoing signal, it is sent when a carrier on a communication line is confirmed again after 15ms after the discrimination of the presence of the carrier and no carrier exists. The incoming signal is sent when the carrier on the communication line is confirmed again at 25ms after the discrimination of the presence of the carrier and no carrier exists. Moreover, when the incoming signal and the outgoing signal are sent at the same time onto the communication line, the transmission of the outgoing signal has priority.
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