Which component activates when power is lost and batteries are used, indicating that other alarms may not function without AC power?

Which component activates when power is lost and batteries are used, indicating that other alarms may not function without AC power?

• A. BMS
• B. PIR
• C. SMPS
• D. Tamper Junction Box

Answer: (C)

When mains power fails, the system must keep operating on its backup power. The switch-mode power supply is the component that handles this transition, delivering stable DC power to the control unit and sensors from the batteries. It detects the loss of AC voltage and automatically uses the battery to keep the alarm system alive, which is why you’d see it activate in a power-failure scenario. The other components have different roles: the battery management system monitors the health and charging of the battery but doesn’t take over power when AC is lost; a PIR is a motion sensor that needs power but doesn’t switch supply routes; and the tamper junction box handles tamper detection, not power switching.

When mains power fails, the system must keep operating on its backup power. The switch-mode power supply is the component that handles this transition, delivering stable DC power to the control unit and sensors from the batteries. It detects the loss of AC voltage and automatically uses the battery to keep the alarm system alive, which is why you’d see it activate in a power-failure scenario.

The other components have different roles: the battery management system monitors the health and charging of the battery but doesn’t take over power when AC is lost; a PIR is a motion sensor that needs power but doesn’t switch supply routes; and the tamper junction box handles tamper detection, not power switching.