SIMATIC S7-400F/FH safety-related automation systems are used in plants with increased safety requirements. They control processes where immediate shutdown presents no danger to personnel or the environment. Two designs are available and they differ as follows:

• S7-400F:
  Safety-related automation system with a single CPU (AS Single Station). If a fault occurs in the control system, the production process is brought to a safe state and interrupted.
• S7-400FH:
  Safety-related and high-availability automation system with two redundant CPUs (AS Redundancy Station). In the event of a fault in the control system, redundant control sections intervene and continue control of the production process.

The additional use of standard modules makes it possible to establish a fully integrated control system for a plant where non-safety-related tasks and safety-related tasks co-exist. The overall plant is configured and programmed with the same standard tools.