The batter, pitcher or catcher simply tap their helmet or cap to challenge — but they only have two seconds. If they challenge, the pitch graphic appears on the scoreboard and broadcast, and the umpire updates the count. The MLB says this takes about 17 seconds.

A computerized system that calls balls and strikes is being tested during Major League Baseball spring training exhibition games starting Thursday after four years of experiments in the minor leagues.

This year's MLB spring training could prove more consequential than any in years past as MLB will experiment with ABS, the Automated Ball-Strike Challenge System, to ensure the home plate umpire gets as many ball and strike calls correct as possible. On Thursday, the league announced how exactly this new challenge system will unfold.