An Automatic Rescue Device (ARD) or Emergency Rescue Device (ERD) is a critical safety feature installed in elevators to ensure passenger safety in the event of a power failure or blackout in a building. These devices are designed to prevent passengers from becoming trapped inside an elevator during such situations. Here’s how they work and their importance:

1. Backup Power Supply: ARD/ERD systems are equipped with a backup power source, such as batteries or a generator, to ensure that the elevator can continue to operate when the main power supply fails. This backup power allows the elevator to return to a designated landing and open its doors, facilitating the safe exit of passengers.

2. Automatic Operation: When a power failure occurs, the ARD/ERD takes control of the elevator. It uses its stored energy to move the elevator car to a pre-determined level, usually the nearest floor, and align it with the corresponding landing.

3. Emergency Communication: In addition to the automatic rescue operation, ARD/ERD systems typically include communication devices such as intercoms or emergency phones. These allow passengers to contact building management or emergency services for assistance or reassurance.

4. Lighting and Ventilation: Elevator cars equipped with ARD/ERD systems often have emergency lighting and ventilation to provide a minimum level of comfort and visibility while passengers wait for rescue.

5. Safety Regulations: Many jurisdictions and elevator safety codes mandate the installation of ARD/ERD systems in elevators to ensure passenger safety during power outages.