The energy reversal beam was a device fitted to Sarah Jane Smith's computer, Mr Smith. It was operated by a lever on a panel. It could be used in conjunction with the sonic lipstick to reverse the effect of an energy restraint device that rooted someone to a floor, so that it would affect the person who activated the device.
While Sarah Jane, Clyde, Rani, and Luke were running a routine check of the computer and about to calibrate this beam, they were interrupted by the arrival of a man calling himself Ambassador Rahnius, who presented them each with headgear. When they and K9 expose him as a member of the Slitheen family, he locks down K9 and freezes the rest of their feet to the ground, using his gifts. With a little teamwork, Sarah and the children use the uncalibrated energy reversal beam in conjunction with the sonic lipstick to reverse the effect, then they returned Rahnius to his point of origin. (TV: From Raxacoricofallapatorius with Love)