Hi Paul, if you keep in mind that the Ross switch machine, the same used by Gargrave and others throws due to a return, or system ground from the push button unit.
This return signal electrical potential is the same as the outside rail of your track. That is why if you use a separate transformer to drive your track switches make sure it is at the same electrical potential as your track.
The isolated track section mentioned above is simply a short section of track, usually on the inside of the switches turn approach that is not electrically connected to the return loop due to a insolated pin at each end of said section. Return is provided through the wheels of your engine, or car when it passes through this section and this return potential is passed onto the input of you switch motor via a 22 gauge wire placed in the same terminal as the command signal wire from your control button for that associated direction of travel.
What ever side of the switch motor you place it ( the wire) on will decide what direction the switch will throw.
IT is very important to remember that of the three motor screw terminals the center one is the + side, or the potential of the center rail of the track. Again that is why a separate switch motor power source needs to be phased with the track power as I stated above.
16 VAC is best to use for these motors, not the 18 VAC recommended for DCS, or TMCC, that is one of the best reasons for a separate Switch motor power source. Again, not to beat a dead horse please see my phasing warning above.
( At your transformers tie the return post or the outside track source together from one transformer to the other).
Have Fun.
