So far all I've used for track laying (on my small practice HO layouts) is Atlas snap-switches (which equate to an 18" radius curve, that much I do know). Now, if I wanted to use 22" curves on my 4' x 8' spring layout (I'm planning the trackage now), do I need #4 or #6 switches?? I'm totally confused. And do I need to worry about this electro/intra/frog thing???? Is there somewhere on the web that would give me a quick lesson as to what all this means, in English???