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Reversing starter
A -> motor starter which determines the rotational direction of a motor. Consists of a circuit-
breaker and two contactors.
Safe state
The basic principle of the safety concept in F-systems is the existence of a safe state for all
process variables. For the digital F-I/O, for example, the safe state is the value "0".
Safety class
Safety Integrity Level (SIL) in accordance with IEC 61508. The higher the Safety Integrity
Level, the more rigid the measures for prevention of systematic faults and for management
of systematic faults and hardware failures.
The fail-safe modules support operation in safety mode up to safety class SIL3.
Safety function
The safety function is a mechanism built into the -> F-CPU and -> F-I/O that allows them to
be used in -> S7 Distributed Safety or S7 F/FH fail-safe systems.
In accordance with IEC 61508: A safety function is implemented by a safety system in order
to maintain or force a system safe state in the event of a specific fault.
Safety message frame
In safety mode, data are transferred between the -> F-CPU and the -> F-I/O in a safety
message frame.
Safety mode
Operating mode of the -> F-I/O which allows -> safety-related communication by means of ->
safety message frames.
ET 200S -> fail-safe modules can only be operated in safety mode.
Safety program
Safety-related user program.
Safety-related communication
Type of communication for the exchange of fail-safe data.
ET 200S Distributed I/O System - Fail-Safe Modules
Installation and Operating Manual, 08/2008, A5E00103686-07
Glossary
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