The APC Back-UPS Pro BR900MI is a line-interactive uninterruptible power supply (UPS) for PCs, workstations, NAS systems, routers, modems, external storage devices, game consoles, and other electronics in home offices and small office environments. It offers an apparent power of 900 VA and an active power of 540 W at a nominal voltage of 230 V. The device is designed as a tower UPS and can be flexibly placed on the floor or on a work surface.

The UPS operates in line-interactive mode and provides a stepped approximation of a sine wave at the output. The typical transfer time in the event of a power failure is 10 ms (maximum 12 ms). It features automatic voltage regulation (AVR), which corrects voltage fluctuations in the mains without resorting to battery mode. The LCD display shows operating status, load, battery status, and other information directly on the device.

The BR900MI offers six IEC C13 output sockets (all with battery and surge protection) as well as a USB interface for connecting to a PC and RJ45/RJ11 ports for protecting network, DSL, and telephone lines. It supports PowerChute software for safe system shutdowns and easy management. The battery is hot-swappable, so the UPS can continue to operate during a battery replacement.