What powers lights, doors, and controls when the main power is offline?

• A. Battery system
• B. Inverter
• C. Multimeters
• D. Clamp meter

Answer: (A)

When main power is lost, essential systems need a separate, reliable source of energy. The backup battery system is designed to supply that energy to critical functions like lighting, door operation, and control circuits. It stores energy and feeds the emergency power bus so these systems keep working long enough to maintain safety and allow safe shutdown or restoration of normal power.

An inverter can convert stored DC to AC, but it still needs a DC source (often the same battery bank) and isn’t by itself the primary power source. Multimeters and clamp meters are measurement tools; they don’t provide drive power to loads.