S4K2U-C and S4K2U-5C Industrial On-Line UPSs are single phase, online (double conversion) UPS available in 500-3000VA, 120V and 230V. 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.