Elevator Emergency Automatic Rescue Device (also known as ARD) is a special device installed in an elevator which is only used during an event of a power failure or blackout in a building. An Elevator Emergency Landing Device (also known as ELD) is useful for preventing passengers from becoming trapped inside an elevator during a power failure. All newly-installed elevators must have elevator emergency automatic rescue device implemented before an elevator examination can pass. However, some countries may not require this device.