If a fire alarm panel loses primary power, it must switch to the secondary power supply within how many seconds?

• A. 5 seconds
• B. 10 seconds
• C. 20 seconds
• D. 30 seconds

Answer: (B)

Automatic transfer from the primary power supply to the secondary (battery) power supply after a loss of AC power is what this question tests. Fire alarm panels are designed to keep operating even when the main power fails, so they switch to backup power quickly to maintain monitoring, signaling, and control.

The standard transfer time is ten seconds. This short window ensures continuous operation without a prolonged power gap that could cause missed alarms, degraded supervision, or failed notifications. If the switch were slower, the system could run on empty battery power for too long; if it were much faster, it might strain the panel’s switching circuitry. Ten seconds provides a reliable, balanced interval for a seamless handoff.