| 摘要 |
PROBLEM TO BE SOLVED: To enable a plurality of slave transmission devices to autonomously establish one-to-multiple communication with one master transmission device without confirming use states of lines and manually operating switches of the slave transmission devices. SOLUTION: The slave transmission devices 2A, 2B, and 2C each generate an alarm signal to be transmitted to the master transmission device 1 through an up line 210 of a bidirectional line when there is not a request-to-send to the master transmission device 1, which transmits a prescribed notice signal to be sent in response to the reception of the alarm signal to a down line 120 of the bidirectional line while receiving the alarm signal through the up line 210. Further, the slave transmission devices 2A, 2B, and 2C each judges the use state of the up line 210 from whether the notice signal is received from the down line 120. COPYRIGHT: (C)2008,JPO&INPIT
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