Micronics UF3300 Manual Del Usuario página 90

UF3300 Modbus
For reliable operation of a Modbus network the cable type and
installation must comply with requirements in the Modbus specification
document:
"MODBUS over Serial Line Specification & Implementation guide
V1.02".
This output is suitable for SELV circuits only.
For full immunity to electrical interference the screen of the Modbus
cable should be connected to Earth.
Three wire Weipu plug/
socket or block
connector
Figure 23 - Recommended Modbus Network Toplogy
Page 2