Siemens SIMOCODE pro C System Manual page 203

Power supply to the inputs of the basic unit
There are three possibilities for powering the inputs:
a): 24 V DC internal
b): 24 V DC external. Input 3 is the reference potential, i.e. three inputs are available.
c): 24 V DC external. Only possible for a basic unit with 24 V DC supply voltage!
Figure 12-14 24 V DC for powering the inputs
All inputs work reaction-free, i.e. the signal statuses on neighboring inputs do not influence
each other.
SIMOCODE pro
System Manual, 05/2019, A5E40507475002A/RS-AD/004
Mounting, wiring, connecting, system interfaces, configuration guidelines
12.2 Wiring, connecting
203