How long must a secondary rechargeable battery provide trouble signals?

The correct answer is that a secondary rechargeable battery must provide trouble signals for a duration of 7 days. This requirement ensures that in the event of a power failure, the alarm system has adequate time to alert users to any issues or faults within the system. The 7-day timeline is a standard reference in alarm system regulations, reflecting the necessity for robust backup capabilities to maintain security and safety. Ensuring that the system can communicate trouble signals over this period provides a safeguard for users, allowing them to address any potential failures before they become critical. This standard supports the overall reliability and effectiveness of alarm systems, underscoring the importance of having a dependable power source in emergency situations.