Siemens SIMATIC S7-400 Reference Manual page 211

M :
I+
M
V+
M +:
M -:
U :
H
(1)
(2)
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
Measuring current (positive)
: Measuring voltage (positive)
Measuring line (positive)
Measuring line (negative)
Auxiliary voltage
Sensor, for example, pressure gauge
4-wire transducer
Analog modules
5.11 Connecting current sensors
211