On-Line UPS systems work very differently compared to Standby or Line-Interactive UPS systems. During normal operation, On-Line UPS systems continuously "remake" input power in a two step process: first, converting AC power into DC power, and then converting DC power back into AC power with a pure sine wave. This two step process allows On-Line UPS systems to supply connected equipment with the best quality output power available. During operation under blackout conditions, the UPS converts DC power from the battery into AC power to support connected equipment. Because its batteries are integrated into its normal operation, On-Line UPS systems take no time at all to transfer between utility power and battery power—0 milliseconds. Zero transfer time allows On-Line UPS systems to reliably support the widest range of devices, even those sensitive to slight transfer times. If an On-Line UPS experiences an internal fault or overload, it will automatically "bypass" its internal components and deliver power directly to connected equipment. In addition, On-Line UPS systems feature an external bypass switch that allows users to perform the same function manually for scheduled maintenance.