Mitsubishi Electric MELSEC iQ-R Series User Manual page 156

Communication method
Communication via the modem function is performed using full-duplex communication.
Connections to devices designed for half-duplex communication is not available.
Data communication to target devices
• Data communication with target devices is performed using the public line or electric wave transmitted from the electric
wave transmission base.
In some conditions, normal data communication may not be carried out due to the system installation environment,
electric-wave transmission status, error in the target device, or other reasons.
Perform a connection test beforehand, and confirm that connection is possible.
7 COMMUNICATIONS BY THE MODEM FUNCTION
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7.2 System Configuration