What types of UPS are available?

 There are three major types of UPS available in the market, each with their own advantages and cost.

Off-Line Units: Off-line units switch from the regular power source to an internal battery when there is a power drop. There is a brief delay between the time the power drops and the time the battery starts supplying power. However this downtime should be brief enough to avoid causing the computer to shut down. On-Line units are normally the cheapest UPS products available.

Line-Interactive Units: Line-interactive units add a transformer to minimise the need for an internal battery to be used with every power fluctuation. These units monitor the line voltage at all times and active the power transformer when the voltage falls below certain parameters. The battery is only ever activate when lower voltages are recorded. There is a brief delay between the time the power drops and the time the battery starts supplying power. However just like the Off-line units this downtime should be brief enough to avoid causing the computer to shut down.