Siemens TR300 Manual page 37

Functional safety
7.1 General safety information
According to IEC 61511-1, Section 11.4.4, the hardware fault tolerance (HFT) can be
reduced by one (values in brackets) for sensors and final controlling elements with complex
components if the following conditions are applicable for the device:
● The device is proven-in-use.
● The user can configure only the process-related parameters, e.g. control range, signal
● The configuration level of the firmware is blocked against unauthorized operation.
● The function requires SIL of less than 4.
The device fulfills these conditions.
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direction in case of a fault, limiting values, etc.
SITRANS TR200/TR300
Operating Instructions, 06/2010, A5E01071992-03