Siemens SIRIUS 3RW5 Equipment Manual page 66

Connecting
5.2 Fieldbus
Terminating resistor for line termination (LT)
On the first and last device in the Modbus RTU segment, place a terminating resistor
between the positive and negative signal.
The 3RW5 communication module contains a built-in 120-Ω terminating resistor. You can
place this terminating resistor using a jumper as shown in the diagram below. If other
terminating resistors are required, use an external bus terminating resistor.
Line polarization
If devices in the Modbus RTU segment require line polarization, you can activate line
polarization in the 3RW5 communication module with a jumper between PU and PD. The
3RW5 communication module contains a built-in 560-Ω resistor pair that is placed by
activation of the line polarization.
Result
The 3RW5 communication module is now properly mounted and connected. You can
integrate the 3RW5 soft starter into the associated network environment.
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SIRIUS 3RW5 Modbus communication module
Equipment Manual, 03/2020, A5E43676481002A/RS-AC/003