Easy, but I can't give a diagram right now. A single Atlas Selector 215, can control four different track sections by itself, many more if you "piggyback" them. Basically, you use the terminals on the left to input your two different throttles, and the terminals at the top to control selected track sections which are isolated from one another with insulated rail joiners. You use the green slide switch to toggle between the two power supplies. Only the (+) wire is used, the (-) or common from your two different throttles are wired together and to the common side of the track to complete the circuit.