An uninterruptible power supply, also called a UPS system, combines a power cord, outlets, power protection, and a built-in battery. The UPS system plugs into your wall outlet, and your devices - such as computers and audio/video components - plug into the UPS system's outlets.
Although a UPS system is sometimes called "a battery in a box," it's actually much more. UPS systems can protect and support equipment ranging from a small desktop computer to an entire data center filled with advanced servers and network equipment.
As long as the electricity stays on, the UPS system passes utility power to the devices connected to its outlets and keeps its internal battery charged. It also protects your devices from power problems it detects, such as power surges and abnormal voltages.
If the power goes out, the UPS system provides connected devices with backup power from its internal battery. This allows your equipment to stay on during a power outage, which is especially useful for devices like computers and DVRs that can lose data when they turn off unexpectedly.