I did not know that the super base B unit had one operating electro coupler. It is just my opinion but I would think that no B unit with the exception of AB sets have a operating coupler. Dummy couples are the way to go on any B unit that is a separate sale item as the non operating couplers are cheaper as well as closer coupling. In fact on my TMCC ABA Alco FA engines I replaced the dummy couplers on the B unit with non operating couples from a E unit as they were even shorter which allowed for real close ABA coupling set. By having a operating coupler on the super base B units you are forced to set up your lash up as a train not a engine in Legacy or TMCC.