A:Answer Only the battery side work, which is the way it is designed. The battery side guards against surges, AND will bridge the power outage, if short, or give you time to shut down if it is one of a longer duration. You can also use software with a computer to get it to automatically shut down your computer if it is on and unattended. The battery side will also kick in to correct Voltages below about 96V and above 140V, keeping it more steady.
The surge protection side only guards against surges and sags, I'm guessing either cutting off the power to keep your equipment from being damaged, OR leveling out the power.