Yes. Well, the decoders, throttles, command stations and so on do. Anything with a microcontroller fast enough to do useful work would fall under FCC certification requirements. Technically, a loco sold with DCC installed would (probably) have to be tested as a complete locomotive "system", but I don't think an aftermarket install into a locomotive would count -- especially not a DIY job. But the rules are a bit tricky with lots of ins and outs, especially when looking at modules intended to be installed in other things.
Generally the requirement is to keep emissions below a certain level so as not to cause interference, and the unit tested must accept any interference from other compliant devices. I believe the emissions requirements are similar (if not the same) as computers and similar items.
DCC equipment is a Class B Digital Device under the FCC Part 15 testing standard. The FCC does not do the testing. Manufacturers do their own testing to assure their equipment meets the technical standards. If we use or operate the equipment according to the manufacturer's instructions, we as consumers do not have to do any testing. - Jeff
