A system comprised of alternate sources of power and all connected distribution systems and ancillary equipment, designed to ensure continuity of electrical power to designed areas and functions of a health care facility during disruption of normal power sources, and also to minimize disruption within the internal wiring system.
Want to learn more? Visit NFPA 70 here: https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=70