| 摘要 |
PURPOSE:To allow the secondary station to discriminate whether or not it receives a normal frame in a short time by utilizing a characteristic that a frame sent by the primary station is returned again to its own station via the secondary station. CONSTITUTION:A primary station 1 sends a frame of a prescribed transmission frame format and secondary stations 2a-2c send the frame to the subsequent station in this order. The secondary stations 2a-2c send a frame different depending whether reception frame is normal or abnormal to the subsequent station by a transmission frame transmission means 51. The primary station 1 uses a reception data comparison means 52 to compare the received frame with the transmission frame to discriminate whether or not the secondary station receives the frame normally.
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