The 1500AVR model has an innovative form that allows the unit to be used as either a free-standing unit, or to be rack mounted. The unit features 2 built in serial ports to allow for control of two computers during a power failure. This model features Automatic Voltage Regulation to insure that your connected equipment receives only regulated, consistent power. The battery-pack has four (4) 7AH batteries for extended runtime and is hot-swappable to minimize downtime. This model is ideal for corporate servers, departmental servers, Unix servers, as well as mission-critical network components.