The Reality Reports

An elevator car may carry several people upward, yet its motor does not lift the entire load by brute force. In many buildings, another heavy object travels in the opposite direction and shares the work. This object is the counterweight. It remains out of sight inside the hoistway, moving down as the car rises and up as the car descends.

Automatic sliding doors appear to perform one simple task. A person approaches, and the entrance opens. Behind that familiar movement is a coordinated system of sensors, controls, motors, tracks, and safety features. The system must notice approaching users without opening for every distant movement. It must also protect someone who pauses in the doorway. These abilities make automatic entrances especially useful for wheelchair users, older adults, parents with strollers, and people carrying packages.