Door operators are used to open and close all types of doors and gates. They use electric, hydraulic, or pneumatic power. Door operators are used to open garage doors and overhead doors, to automatically open doors in high traffic-areas such as grocery stores, and to provide access for wheelchairs. Door operators for commercial applications must be durable and strong to handle repetitive use. They are configured for a variety of door types, including overhead doors, swing doors, and sliding doors. In the United Sates, door operators must comply with the Americans with Disabilities Act (ADA). Overhead door operators and door actuators can lift and lock. Overhead door operators lift a door to allow access. They are used on commercial garages, firehouses, loading docks, and warehouses. Door actuators are a type of door operators can also be used to lock an exterior door. These types of door operators are used to close and lock aircraft cargo and inlet doors by using a motor-driven or hydraulic shaft. Door actuators are also used to secure car doors, and can be programmed to sound an alarm when the door is opened. Door operators are used in commercial settings such as retail stores. Two options for these applications are sliding door operators and swing door operators. Sliding door operators are used to close emergency fire and explosion doors, or to part sectional doors of larger retail businesses. These types of door operators are electromechanical or pneumatic devices that are used in grocery stores, hospitals, and other public places. Typically, swing door openers use a sensor to detect when people approach the door and then close it after a short waiting period. Some models may include a mounted button for activation in case of a malfunction. Swing door operators are another type of door operator for commercial use. Typically, swing door operators are used for smaller retail businesses. Like sliding doors, swing door operators can use a radar sensor to detect a user, or be activated by a push-button. There are three basic types of swing door operators: full energy, low energy, and power assist. Full energy devices open and close the door at full speed. Lowe energy devices open and close the door at a reduced speed. Power-assisted door operators let the user open the door manually at a reduced force.