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IT Support & Hardware · Foundational

Brownout

A sustained reduction in line voltage below normal levels.

Definition

Brownouts can cause computers to reboot, freeze, or suffer hardware stress. They are distinct from blackouts (complete loss) and sags (brief drops). A UPS or line conditioner protects against brownouts.

Example

Lights dimming and PCs restarting when an elevator starts is a sag or brownout symptom.

Exam tip

Spike/surge = brief high voltage; sag/brownout = low voltage; blackout = no power.

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