The function of the so called EPSU is to power the emergency lights and signs in case of emergency if the normal aircraft power is lost. No aircraft power is needed in such a case, as the units are equipped with an energy storage.Diehl Aerospace's EPSU is state of the art, designed with the latest charging and energy storage technology. Highest reliability is mandatory to fulfill all requirements and safety issues. The units are specially designed to the needs: input power and output power (115VAC; 28VDC or 6VDC); communication system (Bus, I/O); power.