When I was talking about switch decoders, I was talking about radio modules that radio manufacturers make but are add ons depending on what you want to control. Switches, motor control, proportional, etc. Most people are probably familiar with this in the Futuaba/Robbe F-14 that you can still get from some RC boat sites. Robbe radios not sold here still have this as well the very popular in Germany, Brixl. If you have seen the leiberrmodelle site and look that is one of their radio options.
Problem is once you spend so much on a radio, you want to use for al your models, but then you only have 1 Tx.
That is why the cheapo Hobby Kings are nice if the functions for the radio suit your build.