Siemens SIMATIC PCS 7 CPU 410-5H System Manual page 265

The following figure shows such a configuration.
Figure 15-12 Example of redundancy with fault-tolerant systems and a redundant bus system with
Response to failure
Double errors in the fault-tolerant system (i.e., CPUa1 and CPa 2) or in the standard system
(CPb1 and CPb2), and single errors in the standard system (CPUb1) lead to a total failure of
communication between the systems involved (see previous figure).
CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB
redundant standard connections
Supplementary information
15.9 Communication via S7 connections
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