TT, N Gauge, N009 and Z gauge

N gauge or N scale is a well know gauge. TT scale is a niche scale, whose name stands for Table Top. It is almost halfway between HO scale (1:87) and N scale (1:160). Its original purpose, like the name suggests, was to make a train small enough to be able to assemble and operate it on a tabletop. Z scale (1:220) was introduced by Marklin in 1972, and is one of the smallest commercial model railway scales with a track gauge of 6.5 mm/0.256 in. Z scale trains operate on 0-10 volts direct current (DC).