APC Back-UPS XS 900VA 120V Battery Backup The APC 900 VA Back-UPS XS offers high performance protection for your business and office computer systems. It provides abundant battery backup power, allowing you to work through medium and extended length power outages. It also safeguards your equipment from damaging surges and spikes that travel along utility, phone and network lines. A distinguishing feature of the Back-UPS XS is automatic voltage regulation (AVR). AVR instantly adjusts both low and high voltages to safe levels, so you can work indefinitely during brownouts and overvoltage situations, saving the battery for power outages when you need it most. Award-winning shutdown software automatically powers down your computer system in the event of an extended power outage. Additional features like audible alarms, LED status indicators, user replaceable battery.