Major League Baseball (MLB) is introducing robots to spring training this year on a trial basis in the form of the ABS (Alternate Ball-Strike System). ABS will peer over the home plate umpire’s shoulder to provide the right call if a team challenges the ump’s ball or strike call.

ABS is MLB’s name for an automated strike zone — also known as robot umps. In a full ABS game, there will be a human umpire behind the plate, signaling the calls communicated through ABS. We won’t be seeing that full system in action this spring. Instead, teams will have a limited amount of challenges.

Starting Thursday at Camelback Ranch, where the Dodgers and Cubs will open Cactus League play, the ABS challenge system will begin being implemented.