Siemens Simatic PCS 7 Function Manual page 16

Basics of high availability
3.1 Motivation for using high availability process control systems
Legend for the above illustration:
Note
The following short designations are commonly used in this documentation.
Short designation
Engineering sta‐
tion
OS server
16
PS CPU CPCPCPCPCP
PS PS IM
PS PS IM
Meaning
Engineering station, PC
Operator station, PC project data station in the project form "WinCC Server"
PS CPU CPCPCPCPCP
IM SM SM SM
IM SM SM SM
High Availability Process Control Systems (V9.0)
Function Manual, 05/2017, A5E39221836-AA
SM SM SM
SM SM SM