Siemens SIMATIC S7-400 Reference Manual page 351

Select the cable length
You select the cable length with the selector switch on the front plate. Set the range
corresponding to the line length. Make the settings on the IM 463-2 only when the CPU is in
STOP mode.
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
S5 interface IM 463-2
7.4 Installing and connecting the IM 463-2
351