OPTICAL AUTO-REVERSING SYSTEM - Large "G" Scale. The Bachmann Large Scale Optical Auto-Reversing System brings automatic point-to-point train or streetcar operation to your railroad. Set up your system, add your train, and watch as it operates back and forth at your specified speed and stopping intervals between two destinations up to 20' apart. Indoor use only. Features include: Large Scale Auto-Reversing Speed Controller and wall power pack, power connector with track clip, two optical sensors with track clips, 3' red power wire, 20' green sensor wire, black double-ended sensor-to- controller wire, works with Large Scale 45mm Track