< As far as the -10 is concerned, there would be several hundred (if not < thousands) of modules and the backplane (for want of a better word) was < machine wrapped nest of identical (yellow) wires. I doubt that you coul < reliably follow a signal within a rack, let alone across the whole machi < However, as I said before, I've never attacked a -10 with a scope so I < can't be sure that this isn't possible. Never touched a 10 myself but... I've worked with those who had. Despite it's complexity most of it is the same thing x36 or some sub multiple. So troubleshoorting it would be like attacking and older straight 8 or 8I/L series with it's large number of modules. You follow a problem along a bit path to the point of failure. Usually with a handfull of know good common modules and a scope. Backplane problems were extermely difficult if there were any kind if damage to the wiring or connectors. Allison