I have battery powered mine, I may have gone to far for some but I ripped everything out and installed all the radio gear, disconnected (and removed) the track power pickup plungers, mine had the Massoth sound which was below par as far as I was concerned, I fitted a Sierra sound card with 2 magnets glued to a tender wheel to activate the sound (gives 3 1/2 beats per revolution but nobody has picked that up).
At present I have an Aristocraft R/C unit installed, that is about to be changed to a Deltang unit, when I can figure out how to trigger the whistle.
Wayne from Oz