Help with wiring

[Russ]

My 6-year-old home is prewired with coax, with a jack in every room. There's a central panel in the master bedroom with an assortment of loose coax ends and four that are connected by a splitter.

The ideal spot for my (C5) antenna is just outside this master bedroom. I plan to use an under-eave mount just outside the bedroom wall, add some mast, and run coax into the attic and down to this panel so as to tie in to the prewired system. (There's a "TV" box on the opposite exterio wall of the house, for incoming cable or dish, I imagine, but I think it's too far to run coax way over there from my antenna.) I'll probably have 3 TV's in the home.

Problem is I'm ignorant about all the cables. They're in two bundles.
Bundle "A" has 5 coax cables labeled N, N, S, 2, and SDT. Bundle "B" has 7 cables labeled 1, 1, 3, 4, SDT, SDT, and S.

The splitter presently has an "S" cable from bundle B coming in on one side, with 3 outgoing cables - N and N from bundle A, and 1 from Bundle B. All the others are loose.

I'm assuming that "S" might mean "signal" and that my new cable from the antenna should be attached to the splitter where the "S" cable is now.

If anyone can help me sort out meaning of "N", "SDT", and S labels and the organization of the cables, I'd be most grateful.

Also, is it generally necessary to use a pre-amp for pre-wired homes like this? There must be a lot of cable in the walls.

Russ