Siemens SIPART PS2 Manual Del Usuario página 20

Connecting device with type of protection intrinsic safety "Ex i"
Basic device "Ex i" (HART)
Note
As auxiliary power, control, and signal circuits, only certified intrinsically safe circuits may be connected.
Figure 9 Two-wire connection, Intrinsic safety "Ex i"
Figure 10 Two-wire connection for 2-, 3-, 4-wire version, Intrinsic safety "Ex i"
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SIPART PS2 (6DR5...)
A5E03436620-01, 03/2011