I was reading a book called "Building A Model Railroad With Personality" (the saga of a western layout named the Jerome & Southwestern) and at some point, the author points out a small handbuilt walkaround control built from an article in an out of print book (ar at least I assume it's out of print, considering the dates). I always wanted one of these handheld contraptions to run my trains, but I want to build it myself for a number of reasons. Has anyone ever attempted this? Would it be practical to transplant the contents of an older transformer to a small handheld unit?