Also in the 1960s Eldon Industries, Inc. produced 1/32 scale slot cars and sets with a very modern lane change system for analogue cars branded Selectronc that used lane change sections with a dedicated lane change controller. The cars and transformer used diodes to separate the control signals from the hand controllers that allowed for both cars to run independently in the same lane. In the mid and late 1970s several manufacturers including Aurora, Lionel and Ideal (USA) introduced slotless racing systems that theoretically allowed cars to pass one another from the same lane. Most used a system of multiple power rails that allowed one car to speed up momentarily and move to the outside to pass. Though briefly successful as toy products, none of these systems worked well enough to be taken up by serious hobbyists. In 2004, a number of traditional slot car manufacturers introduced digital control systems, which enable multiple cars to run in the same lane and to change lanes at certain points on the course. Digitally coded signals sent along the power strips allow each car to respond only to its own controller. In addition, imaginative manufacturers have used the slot track system to allow the racing of a variety of unusual things, including motorcycles, boats, airplanes, spacecraft, horses, fictional and cartoon vehicles, snowmobiles, and futuristic railroad trains. Slot car tracks The first sectional slot tracks from Scalextric and VIP were molded rubber and folded metal, respectively, but modern slot tracks fall into two main categories: plastic tracks and routed tracks. Plastic tracks are made from the molded plastic commercial track sections. Sectional track is inexpensive and easy to assemble, and the design of the course can be easily changed. The joints between the sections, however, make a rough running surface, prompting the derisive term "clickety-clack track". The many electrical connections cause voltage drop and contribute to more frequent electrical problems. For a permanent setup, the joints can be filled and smoothed, and the power rails soldered together or even replaced with continuous strips, but the surface is seldom as smooth as a good routed track. Routed tracks have the entire racecourse made from one or a few pieces of sheet material (traditionally chipboard or MDF, but sometimes polymer materials) with the guide-slots and the grooves for the power strips cut directly into the base material using a router or CNC machining. This provides a