Emergency lighting devices for generator systems switch lights to a building's backup generator or central inverter system to keep light fixtures lit for a specific amount of time if the main power supply to the fixtures goes out. This lets people in the surrounding area see where they're going as they evacuate. Also known as generator transfer devices, or GTDs, these devices will turn on light fixtures during a power outage even if the switches that control the fixtures are in the off position. Emergency lighting devices for generator systems help building owners meet code requirements for emergency lighting without having to install separate emergency lighting fixtures. They are used with lighting systems in hospitals, universities, and other large facilities that have backup generators or central inverter systems that kick in to supply power to the facilities in the event of a power outage.