When the building is a Class A high-rise building, the two power supplies are the main power supply and the emergency power supply. Emergency Power System: NEC Article 700 specifies electrical safety requirements for circuits and equipment that must operate to enable the evacuation of buildings where large numbers of people assemble, such as hotels, theaters, areas, and healthcare facilities. Circuits and equipment that provide. plan and implement an emergency lighting installation, that satisfies all the legal requirements, and ensures safe evacuation in the event of an emergency. This guide is based on common European standards and practices.