Controls: Lionel type-ZW transformer with Lionel Legacy and MTH Digital Command System Accessories: Gilbert American Flyer, K-Line, Lionel, Z-Stuff for Trains Structures: Crescent Locomotive Works ...

He explains it in his own words in the demo video. The sensor was small enough for an N-gauge train, which translates to 1:148 scale or about 9mm from rail to rail. His idea was to build a tiny ...