P+F manual states that "Isolated barriers are a combination of an intrinsic safety zener barrier and a galvanic isolation network". What is the use of a galvanic isolation network? What components are used in this? Can someone explain the internal construction of a P+F STC (smart transmitter supply) barrier to get a better understanding of this concept? I cannot understand how the output terminal going to DCS from the barrier is connected to this network which connects power supply and field devices.