As a followup to stevenh's excellent post
on DCC lighting without a decoder, I offer a counter-point:
DCC Lighting with a decoder, but when you can't modify the lightboard.
http://akihabara.artificial-science.org/2008/12/27/dcc-and-end-cars-the-no-cut-conversion/The upshot is that, if for whatever reason you can't cut up your existing lightboard, you can build an auxiliary circuit to sit between the decoder and the lightboard that emulates DC power on the track. This works with all sorts of mobile lighting applications, but it ends up being more complex than actually modifying the lightboard if that is a possibility.
