South Jackson yardmaster Bill, a guest operators, prepares to send train 200 on its way after a block swap. South Jackson is a bit cramped and it's easy to get yourself jammed up, especially if the blocking order of trains arriving isn't correct. Bill is doing a great job. There are two holes in the backdrop. The one on the left is the mainline leading to Toh Junction and the helix down to main staging. The one on the right is for the South Jackson switch lead. It is fairly long and has detectors on the end. When there are 4 cars of room left the detection circuit will beep. When there are two left, it will beep twice. When there's one car left, it will beep three times.