Friday's tilt between the Red Sox and White Sox marked the first use of instant replay at Fenway, which christened the start of this three-game set between two American League pennant contenders.
A locked box, equipped with a television monitor and phone, sits in a room just behind the home dugout down the first-base line. If there is a question about home run calls -- such as if a hit is fair or foul, over the fence or not, or a fan potentially interfered -- the crew chief umpire has the ability to check the replay.
During the course of a game, if there is a disputable call stemming from a borderline home run ball, the umpire crew chief would have the option to go into the room with the instant replay box and view what happened.
He would review the play in question by using a television monitor and a secure telephone link to MLB Advanced Media's headquarters in New York.
The crew chief would call a MLB technician using the secure line, who would transmit the most appropriate video footage back to the stadium.
The reviewed play should take two to three minutes before judgment is finalized.
No additional cameras are in place at Fenway to help aid the instant replay, Red Sox spokesman John Blake said.
Instant replay made its Major League debut in three series on Thursday, due to each being a case of a four-game set over the weekend: Cubs and Phillies, Rangers and Angels, Twins and A's, but the technology wasn't used in any of the series.
The remaining clubs began using instant replay on Friday for the start of the remaining three-game sets.
Mark Remme is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.