Siemens SCALANCE M812 Operating Instructions Manual page 46

Connecting up
4.4 Digital input/output
Digital input
The 2-pin terminal block has the following assignment:
DI+
DI- (input ground)
If there is an adequate switching voltage at the digital input, the digital input is active and the
"DI" LED is lit.
46
24 VDC
-
Operating Instructions, 08/2018, C79000-G8976-C331-06
SCALANCE M812, M816