Resistance type controllers can be used with either positive or negative track wiring, most electronic controllers can only be used with one Vintage ho scale slot car the other, although a few electronic controllers feature a switch that adapts them for either gate configuration. In the s, computer design and methods of printing on 3-D objects helped create much more detailed and authentic models than the simple shapes and rudimentary graphics of the slot car boom. HO slot cars work on a similar principle, but the current is carried by thin metal rails that project barely above the track surface and are set farther out from the slot. Later versions had an intermediate speed, Vintage ho scale slot car one late version used a buzzer mechanism to provide full-range speed control. Plastic tracks are made from the molded plastic commercial track sections. HO Slot Car Racing.