Under normal operation, how long can a central station fire alarm secondary power maintain functionality without interruption?

The correct answer reflects industry standards which dictate that a central station fire alarm's secondary power supply should be capable of maintaining functionality for a specific duration during a power outage. In this case, the standard duration is 24 hours.

This is critical because, in the event of a power failure, it is essential for the fire alarm system to remain operational to ensure safety and prompt response to emergencies. The 24-hour requirement ensures that during a power disruption, the system can continue to monitor for alarms and communicate with emergency services, thus minimizing risk to life and property.

Other durations listed do not align with common industry standards for central station fire alarms in terms of backup power capabilities, demonstrating that while longer durations may seem favorable, they are not the set requirement for ensuring compliance and reliability of fire alarm systems in practice.