Thank you for your advice!

I have a Crown Edition Williams F7 AA set that has 2 motors in both units, and no horn or bell because the older, larger reversing board that leaves insufficient room to add the True Blast unit.  However, I purchased a matching F7 B unit, and I plan to install the True Blast diesel sound module inside the interior of B unit.  I will need to install a set of central rail rollers for the dummy trucks.  (I've ordered the sound board and the center rail roller kits already.)   The question I have is this:  the True Blast board is set up to get its power from the reversing unit board.  Can it be direct wired from the AC power coming in from the track?  Or does it need something like a wave bridge rectifier (which would convert it to DC)?  I wasn't sure, but my understanding of how the horn and bell works is that a DC pulse is overlaid on the AC from the transformer when the horn switch is pressed.  Thanks for any help or advice you can provide.