SPS
Short for Standby Power Supply, a SPS contains a circuit that has the capability of telling if and when a disturbance in electricity occurs. When a disturbance occurs, the SPS switches to battery power. Unfortunately, however, if the SPS switch time is not fast enough, all power may still be lost. Higher quality SPS systems offer a ferroresonant transformer that offers a small amount of power while switching takes place.
Also see: Power definitions, UPS