What type of components does the hot battery bus provide power to with the battery switch off?

The hot battery bus is designed to supply power to critical components even when the battery switch is turned off. One of the main functions of the hot battery bus is to ensure that essential safety systems remain operational in case of an emergency. The components that are traditionally powered through the hot battery bus include the firewall shutoff valves, which can prevent fuel from flowing in case of a fire, and the engine fire extinguishing control switches, which allow the crew to activate fire extinguishing systems if a fire is detected.

This capability is crucial because it enhances safety during situations where power may otherwise be unavailable. The ability to access these systems regardless of the battery switch position ensures that crews can react promptly to fire emergencies, directly safeguarding both the aircraft and its occupants.

In this context, while other systems may require power for normal operations, they do not share the same level of urgency that the firewall shutoff valves and fire extinguishing control switches provide in emergency situations, making them less appropriate answers in relation to the hot battery bus's critical role.