Unless i'm missing something here, the old TAS TMCC Whistle Controller Board provided the DC offset in both a command and conventional environment needed to operate an existing whistle or horn. It was p/n TAS 1308.
Here is a reprint of the intro on their instruction sheet,
"The TMCC Whistle Controller Board is designed as an add-on upgrade to any of TAStudios’ command control upgrade boards without sounds. The Whistle Controller is designed to receive and decode the serial data stream from the R2LC command receiver and generates a positive DC offset to activate a conventional whistle or horn soundboard. This board only activates the whistle or horn, not the bell. Once the TMCC Whistle Controller is installed it will operate in both a command and conventional environment."
I used them with both the Digital Dynamics DC Deluxe and the ERR DC Commander. Never tried it with the old Lionel LCRU. They have been out of production for as long as TAS has been gone; seems they used to retail for about $25 and they still can be found in some hobby shops. In fact i may still have dead one in my junk box.
As far as a station bell, i simply recorded one on a chip, powered it with a battery, mounted it and a speaker under my station platforms, and wired it to a push button for realistic sounds when trains are entering the station.
jackson, CEO of the Not-So-Great-Eastern R.R.
aka The Never Done Lines
http://www.youtube.com/watch?v...&feature=channel