Figure 1 depicts the trend as seen in communication architecture found in process automation.
The dotted line represents an optional wireless link, whereas, the solid lines represent wired communication links. As can be seen from the figure, the move from 4-20 mA current loop (i.e. commonly used analog sensor signaling standard) to the fieldbus technology offered considerable reduction in required cabling, and this next phase of transition using wireless technology further eliminated most of the cables.