Larry,

Thank you for your response. That all makes sense.

Just allow me to display my ignorance further.

So, I have a transformer plugged into the wall. and on it our 4 towers that come off. 2 sets. One is adjustable voltage and the other is for the max. I connect my white and black feeder wires, that are soldered to the inside and middle track. Trains run just fine and the switcher lights up.

Where I got confused is the use of the term power terminal and common terminal. All I have is black and white feeder wires that connect the transformer to the track. I see a single wire in the diagram attaching to the fixed voltage plug on the switcher, what one wire is that?

Much appreciated and assume I know less than you expect.