The steps of an escalator ride on a rotating chain assembly.

­Escalators are one of the largest, most expensive machines people use on a regular basis, but they're also one of the simplest.

At its most basic level, an escalator is just a simple variation on the conveyer belt. A pair of rotating chain loops pull a series of stairs in a cons­tant cycle, moving a lot of people a short distance at a good speed.

In this article, we'll look inside an escalator to find out exactly how these elements fit together. While it is exceedingly simple, the system that keeps all the steps moving in perfect synchrony is really quite brilliant.

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