S4K2U-C and S4K2U-5C Industrial On-Line UPSs are 1 ph, online (double conversion) UPS available in 500 to 3000 VA, 120 VAC and 230 VAC. Online design means zero transfer time from external to internal power, so when utility power fails, your critical load remains supported by a seamless flow of power. Housed in a slim 2U package, the rack or tower configurable S4K2UC offers a higher power factor, longer battery life, higher reliability and reduced cost of ownership.