Mitsubishi MELSEC-A Series Reference Manual page 325

10. TROUBLESHOOTING
When a MELSECNET/B data link system is used
In a MELSECNET/B data link system, since the link cables for both send and receive
operations are connected to the same terminal block, data link operations can be
continued even if power supply to one of the local stations is turned OFF.
Replace the link module of a faulty station as shown below:
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