Editing Uninterruptible power supply (section)

===Offline/standby===
[[Image:Standby UPS Diagram SVG.svg|thumb|350px|Offline/standby UPS: The green line illustrates the flow of electric power. Typical protection time: 5–20 minutes. Capacity expansion: Usually not available.]]

The offline/standby UPS offers only the most basic features, providing surge protection and battery backup. The protected equipment is normally connected directly to incoming utility power. When the incoming voltage falls below or rises above a predetermined level the UPS turns on its internal DC-AC inverter circuitry, which is powered from an internal storage battery. The UPS then mechanically switches the connected equipment onto its DC-AC inverter output. The switch-over time can be as long as 25 milliseconds depending on the amount of time it takes the standby UPS to detect the lost utility voltage. The UPS will be designed to power certain equipment, such as a personal computer, without any objectionable dip or [[Brownout (electricity)|brownout]] to that device.