The secondary power supply for an emergency voice/alarm communications system must operate for how long in normal standby mode and then for at least how long in a fire or other emergency condition?

The secondary power supply for an emergency voice/alarm communications system must operate for how long in normal standby mode and then for at least how long in a fire or other emergency condition?

• A. 12 hours / 30 minutes
• B. 72 hours / 2 hours
• C. 24 hours / 15 minutes
• D. 48 hours / 60 minutes

Answer: (C)

Secondary power must keep an emergency voice/alarm system operable under two conditions: while in normal standby and during a fire or other emergency. It should provide power for 24 hours in standby, ensuring the system stays ready even if the main supply is unavailable for a day. In a fire or emergency, it must sustain operation for at least 15 minutes, giving time to issue alarms, coordinate with responders, and guide occupants to evacuate. This combination aligns with standard life-safety requirements for emergency communications systems (NFPA 72). The other duration pairs either place too short or too long a window for emergency operation or don’t match the code’s timings.

Secondary power must keep an emergency voice/alarm system operable under two conditions: while in normal standby and during a fire or other emergency. It should provide power for 24 hours in standby, ensuring the system stays ready even if the main supply is unavailable for a day. In a fire or emergency, it must sustain operation for at least 15 minutes, giving time to issue alarms, coordinate with responders, and guide occupants to evacuate. This combination aligns with standard life-safety requirements for emergency communications systems (NFPA 72). The other duration pairs either place too short or too long a window for emergency operation or don’t match the code’s timings.