Shamus, et al Shamus, I tried to send you a private note so as not to take uop space here, but was notified your box is full and what the heck, maybe others are struggling with this sort of thing just like me. I am back to my loop wiring problem. I have in front of me your wiring diagram. I also have an Atlas #220 controller. Is this the kind of controller you reference in your diagram, or something similar? My other question is: what makes it necessary to have more than one power pack. Is it simply based on the number of cabs you wish to operate? I am block wiring which I know makes a difference Bob Anyone else who wants to add their 2 cents worth please jump in. I can always use all the help I can get!!