There are three types of UPS systems that are designed to give you backup power in case of power failure or a blackout. Basically, what they do is that they act as a buffer between the utility power supply and your electrical equipment, providing power from batteries when needed. There are two types of standby systems: “offline or standby” and “line-interactive“. The difference between the two systems is in the power. As the name suggests, the online (or double-conversion) UPS power supply converts power twice (AC to DC and DC to AC) and stays always on. It also provides PFC (Power Factor Correction) within its rectifier module. As AC power gets drawn from the utility along.