Hey, I just remembered! NAVS has a few Packs here in The f/L that has Sound Lines Targeted for Sound-Range Operation that Open-Rails Reads-Only. 2 I can think of are, The EMD 16-645 Roots & TE Sounds( has others within, It Explains ), & A Kit for Tyler's IC SD40 Sets. Each one has a built-in( so to speak ) added-on Bell Command With-in The Sound Lines. Maybe You could get Inspiration as to where The Bell Command(s) needs to be Located from there one of those?