I think the difference is, SC2 accepts the TMCC/Legacy signal without being hard wired into the layout? The ASC2 is hard wired and daisy chained with the ability to add others. My layout is all Cab 1/Cab 2 controlled, I utilized the ASC’s, BPC’s which are hard wired into the layout and daisy chained together. These are the first ones offered, a little different from the ASC2, BPC2. Now, the SC2 and the ASC2 can be a great electronic switch to operate your switches/turnouts, and most accessories via Cab 1 or Cab 2. Simply read the directions on each. Good luck and have fun with these helpful alternatives to powering our layouts.