dbest, I'm glad my explanations so easy to understand.  I agree that trying to understand SCADA from a field/control engineer's perspective is daunting.  It reminds me of my college days taking EE courses.  They seemed to explain the simplest concepts in the most complicated ways.  But in a way, it makes sense.  They are trying to explain the concepts in the context they learned it, which is basically from the ground up with no per-conceived understanding.  My hopes were that I'd be able to shortcut this process and bridge concepts most of use are familiar, giving IT professional at least a basic working model of SCADA and Smart Grid systems.  I'm glad to see that it is working for at least one of the readers.  ;-)