- Emergency source of electrical power – A source of electrical power intended to supply the emergency switchboard in the event of failure of the supply from the main source of electrical power, (acc. to SOLAS Chapter II-1, Part A).
- Main source of electrical power – A source intended to supply electrical power to the main switchboard for distribution to all services necessary for maintaining the ship in normal operational and habitable condition, (acc. to SOLAS Chapter II-1, Part A).