Ron, now we are getting someplace.
One thing you want to know is how to wire that atlas piece.Southern gave the explanation but it would help to see it wire up or find the instruction.Keep in mind that they are a three way switch.
Have fun get 4 pieces of track.Attach one transformer. Run the train back and forth. Then place a pair of insulators in the midddle. Run the train.Notice what happens. Then attach a second pair of wires from the track to the transformer on the other side of the insulators with each lead the same as the first set.RUn the train and notice what happens. This is all optional. Now the next step run the train to one side stop it. the reverse the wires to that side. What happens. Warning!!! Stay on that sidewith the engine.
You just created a block and reversed the current.
The engine will not run on the other side because one side is reversed the engine will go in reverse when it crosses over. THIS is NOT GOOD. You can break the motor. It is like shifting a car in reverse when you are still going forward it just doesn't work.
Next step is to show you how to use that atlas piece and wire it to your four pieces of track
This is a general diagram the 3 way swiches (DPDT)are in the middle, track on top, and transformer on the bottom.
Atlas? I need a book on how to wire. Many switches selectors and controllers available. Hopefully they come with a diagram. Feel free to modify my attempt.
Ron showes an atlas 215 selector.