In the event of a failure of the main electrical power supply on a ship, certain circuits must be fed from the emergency source of power to ensure the safety and operational capability of critical systems. These circuits are essential for maintaining the functionality of key equipment and systems that are essential for the safety of the vessel and its crew. The selection of these circuits is based on several factors aimed at prioritising important functions and ensuring the vessel's ability to respond to emergencies effectively.

1. Steering Gear Motor: The steering gear motor is essential for controlling the direction of the vessel, ensuring manoeuvrability and avoiding collisions, especially in emergency situations.
2. Emergency Fire Pump: The emergency fire pump is vital for supplying water to firefighting systems in case of fire onboard, helping to contain and extinguish fires to prevent them from spreading.
3. Emergency Air Compressor: The emergency air compressor provides compressed air for starting from a dead ship or if all the air from the main air bottle is lost.
4. Breathing air compressor: for filling SCBA bottles that can be used during fire fighting and entry into enclosed spaces.
5. Sprinkler/Hi-fog Pump: These pumps are responsible for spraying water for fire suppression to control and extinguish fires in different areas of the vessel.
6. Fire Detectors: Fire detection systems continuously monitor various areas of the ship for signs of fire or smoke, providing early warning to enable prompt response and evacuation if necessary.
7. Navigation Equipment: Navigation equipment, including radar, GPS, and gyrocompass systems, is essential for maintaining situational awareness, determining the vessel's position, and navigating safely, especially in adverse weather conditions or restricted visibility.
8. Communication Equipment: Communication systems, such as radios, satellite communication terminals, and distress alert systems, enable the crew to communicate with shore authorities, other vessels, and emergency responders in case of distress or emergencies.
9. Watertight Doors: Watertight doors are important in maintaining the vessel's watertight integrity and preventing the ingress of water in case of flooding or damage to the hull.
10. Lifeboat Davits: Lifeboat davits are used for launching lifeboats and rescue boat, providing a means of evacuation for the crew and passengers in emergencies such as abandon ship.
11. CO2 Room Exhaust Fan: The CO2 room exhaust fan is essential for ventilating the spaces where carbon dioxide (CO2) fire suppression systems are installed, ensuring that the room is safe to enter.
12. Engine Room Vent Fan: One of the Engine room blower power is supplied from the Emergency generator, which helps in air supply to E/R and provides safe entry to the Engine room.
13. E/R Pumps and Systems for First Start from 'Dead Ship': These pumps and systems are necessary for restarting the required pumps and systems in the engine room, enabling the vessel to restore power and propulsion from a state of complete power loss ('Dead Ship').
14. Emergency Lights: Emergency lights are provided in the Engine room, accommodation, upper deck, escape routes, stairwells, and muster stations, ensuring visibility during power outages or emergencies.
15. Battery Chargers: Battery chargers maintain the charge of essential batteries, including those for emergency lighting, communication equipment, and control systems, ensuring their readiness for use in emergencies.
16. E/R Alarm System: The engine room alarm system monitors various parameters and conditions in the engine room, providing early warning of abnormalities, malfunctions, or hazards that could jeopardise the safety and operation of the vessel.