Siemens TR300 Manual page 35

Functional safety
7.1 General safety information
Functioning of the system as shown in the example
The transmitter generates a process-specific analog signal. The downstream control system
monitors this signal to ensure that it does not fall below or exceed a set limit value. In case of
a fault, the control system generates a failure signal of < 3.6 mA or > 22 mA for the
connected positioner, which switches the associated valve to the specified safety position.
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SITRANS TR200/TR300
Operating Instructions, 06/2010, A5E01071992-03