Emergency generator set
A generator set that is permanently available and intended to be brought easily into service when another supply has failed.
Note: 1 An emergency generator set that is brought into service when the regular supply has failed and that provides comparable service is called a standby generator set.
Note: 2 An emergency generator set that is brought into service when both regular supply and emergency supply have failed may provide a greatly reduced service.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM