The current collector of an electric locomotive is called a pantograph, from its construction of slender links that move like a pantograph, although it is not a pantograph at all, but an example of lazy tongs. If s is the length of a link in lazy tongs of N sections, then they will extend a distance of x = 2Ns sin θ, where θ is the angle shown in the figure. It is easy to find the velocity ratio dx/dθ, and so the "leverage" of the tongs