This on-line double-conversion UPS system maintains perfect output by converting AC input to DC, then reconverting UPS output to fully regulated sine wave AC. Constant on-line operation completely isolates sensitive equipment from every power problem on the AC line. The SmartOnline® SU2200RTXLCDN provides the highest level of power protection and battery backup for education, healthcare, military, government and other mission-critical IT applications where space is limited, but premium power reliability is essential.The field-replaceable, hot-swappable VRLA battery modules allow you to work through short power failures and give you enough time to safely save files and shut down your system in case of a prolonged blackout. Zero transfer time between on-line and battery modes maintains continuous operation of connected equipment without interruption or rebooting. Extra runtime is available by connecting up to four optional extended battery modules (BP72RT, sold separately).