Quoted from http://www.pinrepair.com/sys1/

"Every System1 pinball has two relays mounted under the playfield. These are the Game Over Relay (Q), and the Tilt Relay (T). The Game Over relay activates and stays energized all during a game. This turns the 24 volt power on for the flippers, pop bumpers and slingshot coils. It also turns off the Game-Over light in the backglass."