The ATEN Professional Online UPS is an exceptional and innovative electrical apparatus that provides emergency power to a load when the input power source, or the mains, fails. The basic technology of an online UPS is the same as in a standby or line-interactive UPS, however, the ATEN Professional Online UPS provides a much greater current of AC-to-DC battery-charger/rectifier where the rectifier and inverter are designed to run continuously with improved cooling systems.