The Power Booster
Power Booster is Buffalo’s name for the little auxiliary power box that comes with the external hard drive. Think of it as a kind of "mini UPS". Both the input and output USB cables are integrated into the device and cannot be removed. The box is plugged between the computer’s USB port and the external hard drive, and helps to ensure adequate power supply to the drive. Should your USB port be incapable of supplying enough peak current for spinning up the hard drive, the Power Booster comes into action.
It will start buffering energy from the USB connection into a built-in battery as soon as it is plugged to an active computer system (powered on or in standby). It also terminates power to the drive until it is sufficiently charged for the hard drive to start. This took only few seconds with our test system, as the USB port obviously was capable of powering the drive itself. As soon as the drive is powered up, the Power Booster will only keep charging its own battery.