Siemens SIMATIC S7 Functional Safety Manual page 204

Glossary
Proof-test / Proof-test interval
A proof test is a verification that a safety component or system operates as expected.
Immediately after each successful proof test, the safety component or system is considered
to have a minimum probability of dangerous failure. The probability of dangerous failure
increases with time until the next proof test. The maximum probability of dangerous failure is
calculated assuming the component or system is tested or replaced within the proof test
interval.
Quality bit
The data bit accessible to the user program indicating whether or not a safety I/O channel is
passivated. If the quality bit is "0", the channel is passivated or deactivated. For a 1oo2 input,
the low numbered quality bit is effective, and the high numbered quality bit is always 0.
Reintegration
The procedure that allows a passivated channel or module to become active again after
diagnostics indicate that faults are removed or corrected.
Safe state
The basic principle behind the safety concept is the identification of a safe state for all
process variables. The value "0" (de-energized) represents this safe state for digital fail-safe
signal modules (SM). This applies to both sensors and actuators.
Safety Administration Editor (SAE)
A view in the TIA Portal, for each PLC, allowing the user to configure safety program
scheduling and time out parameters, identify the safety blocks and data types, and set
protection for the safety program.
Safety function (context: PLC internals)
The term "safety function" can refer to PLC system internal features, including program block
elements, that contribute to the development of your safety program and the assurance that
your user or application safety function is executed as designed.
Safety function (context: user or application level)
One specific action of a safety system. While the term can be used for general goals (for
example, "Protect the operator from the saw blade"), safety system analysis typically
includes decomposing the general goal into elemental specific actions designed to minimize
risk (for example, "When the hand control is released, turn off the motor" or "Keep the
access guard locked until the motor has been deenergized for at least 60 seconds"). Each of
these items can be considered a safety function.
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S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA