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 ...

The Atlas N Alco RSD5, a six-axle road switcher, is a Classic line model now offered with an ESU LokSound V5 sound decoder.

In his September 2015 article "American history on an N scale diorama" Mike Blumensaadt listed sources for the 1:160 model ...

For those working in the N scale, there’s now an easy way of observing your project as the train driver would see it: [Vassily98] managed to squeeze a wireless camera into an N-scale railcar.