Does anyone know of a place, or magazine article(s) that discusses the various ways steam locomotives are wired for power pick-up? I have 7 or 8 narrow gauge (HOn3) steam locos by various manufactures (PFM, Tenshodo, etc.) from the late 60's and the 70's. One or two have sound capability. Now, most are "plug and play", meaning connect tender to loco by way of a stud on the tender to the loco drawbar, which usually has a thin spring wire for continuity. Some have very small wires which need to be connected to the tender along with the drawbar connection, otherwise the loco won't run..... Are there any diagrams which show all the possible wiring techniques in magazines or on the internet, perhaps in this forum? It is very confusing trying to understand how these various wiring situations work! I wonder if sound units have loco power going thru them, hence, rewiring standard drawbar connections. Any info will be greatly appreciated! Thanks.