The Smart-UPS On-Line products are based on field proven, industry leading Smart-UPS functionality but offer a double conversion on-line topology that delivers tight voltage and frequency regulation, zero transfer time to and from battery, and input power factor correction. While offering advanced performance and high availability features, the Smart-UPS On-Line can be managed using APC's PowerChute plus software as well as an array of SmartSlot accessories. Smart-UPS On-Line UPSs provide battery back up to the load through the use of internal batteries. An unlimited number of external battery packs (part # SUOL48XLBP) can be added to scale the runtime to desired levels. All UPSs and battery packs ship as a tower, but can easily be converted to a 19" rack-mount configuration with the addition of a Rail Kit (part # SUOLRK). Smart-UPS On-Line is a high performance UPS for servers, networking equipment, telecommunication systems, industrial and medical equipment, and other mission-critical applications.