That is up to the manufacturer. Company sites have plenty of information. I don't want to lead you astray. I understand they are, but some have more features than others. This is just a general answer for a general question.
Try this: http://cs.trains.com/trccs/forums/744.aspx
A forum community dedicated to model train owners and enthusiasts. Come join the discussion about brands, various scales, repairs, storage, displays, reviews, accessories, classifieds, and more!