An uninterruptible power supply (UPS) is an electrical device that provides near-instantaneous emergency power to connected equipment when the main power source fails. A UPS differs from a generator in that it responds instantly — it continuously supplies power from its internal batteries, with no gap when the mains fail. Most UPS units are sized for short run times (typically 5–20 minutes), enough to allow equipment to be gracefully shut down or for a generator to start. They also condition the power, protecting connected devices from voltage spikes and sags.
A UPS connects between a wall outlet and the devices it protects: it plugs into the AC wall outlet, charges its internal batteries from that supply, and provides its own AC outlets for downstream devices.
In This Home
The [APC UPS](50-Devices/Home Network/APC UPS.md) in the lab protects the network and server equipment from brief power outages. It is part of the [Home Network](30-Systems/Home Network/index.md) system.