Siemens SIMATIC PCS 7 Function Manual page 21

Basics of increased availability
Increased availability in PCS 7 is based on the following principles:
● Duplication of a component
Example:
Use of duplicate signal modules
● Duplication of a component and a software component that performs an automatic fail-over
from active and passive components in the case of malfunction.
Example of redundant components:
A signal is acquired with two signal modules and the redundancy software. The failure of
one module remains non-critical for operation of the plant.
● Technical solutions for configuring components that prevent the failure of a sub-component.
Example:
Configuration of a network in a ring topology with redundancy manager component. If part
of the ring is disrupted (by a defective cable, for example), the operation of the network is
maintained.
Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA
Basics of Fault Tolerance
2.4 Overview of the PCS 7 redundancy features
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