Hmmmmm, this is an interesting question! I have 3 sets of rails, 2 main lines and 1 yard rail. They are all approximately 150 feet long, plus a 6 shelf display cabinet that takes up entire wall and all are powered by a single unit with a 8 amp booster, that I only use when I fire up my MTH HO train, which likes 16 volts. Included are 16 lighted passenger cars and 12 lighted caboose. I found out that if I keep all units a minimum of 8 feet away from section where the track wires are attached, when I shut down, I have no start up problem. My display connection is between power supply and rails and I had to install a disconnect switch to correct the problem there. Once I am powered up, I can throw the switch and power the display to demonstrate those units. All units, 17 trains and all with their own cars, are DCC with sound. I soldered all my joints, however, and developed an expansion problem resulting in loosing connections. I corrected this by my own invention of an expandable soldered connection! I used extra small phosphor bronz wire, bent it in shape of a square horse shoe and placed at connections that came loose. This allows a small expansion crack with no power lose. But I have a camera train to help me find them, however. It is powered from the track and will let you know when you have a bad rail connection. I didn't learn all of this overnight, however, as it was a 6 year trial and error method. But anyhow, that is part of the fun of railroading. I don't have much fun anymore, as it all runs trouble free now! Happy motoring!