n.
Moving staircase used as transportation between floors or levels in stores, airports, subways, and other mass pedestrian areas.
The name was first applied to a moving stairway shown at the Paris Exposition of 1900. Modern escalators are electrically powered, driven by chain and sprocket, and held in place by two tracks. As the treads approach a landing, they pass through a comb device; a switch cuts off power if an object becomes jammed between comb and treads.