Operating As An Rs-485 Interface; Figure 2: Rs-485 Bus Termination - WAGO Compact Controller 100 Manual

WAGO I/O System Compact
751-9301 Compact Controller 100

4.1.3.6.1 Operating as an RS-485 Interface

To minimize reflections at the end of the line, the RS-485 line must be terminated
at the end at a line termination of 120 Ohm. The RS-485 line is already
terminated in the Compact Controller 100 with a bus terminating resistor (120
Ohm). A bias network (pull-up and pull-down resistor) is also integrated in the
Compact Controller 100 to keep the bus lines at a defined level when no other
subscriber is active.
Attention — bus termination!
The RS-485 bus must be terminated at the end!
No more than two terminations per bus segment may be used!
Terminations may not be used in stub and branch lines!
Drop cables must be kept as short as possible!
Operation without proper termination of the RS-485 network may result in
transmission errors.

Figure 2: RS-485 Bus Termination

Version 1.1.0, valid from FW Version 03.08.07(20)
Properties 31
Manual