NFL referee Pete Morelli reviews a play during a preseason game between… (Jamie Squire / Getty Images )
Examples of how other pro sports use replay:
Officials can use replay to see if a shot was released before time expired. Replay also determines which players should be ejected after a brawl or flagrant fouls. Replay can determine if a shot is worth two or three points, or to decide possession on balls that go out of bounds. It may also be used if the game clock malfunctions to determine the correct amount of time left. Beginning this season, it can be used to review a block/charge play to see if the defender was inside or outside the restricted area. Also this season, it can determine if an off-ball foul occurred before or after the ball is released.
The video goal judge reviews replays of disputed goals. Examples include if the puck crosses the goal line completely before time expired or if a puck is in the net before it is dislodged. Replay can also be used to determine if a puck is directed into the net by a hand or foot or if it is deflected into the goal by an official or high stick.
Each coach is allowed two challenges on certain reviewable calls as long as it is not in the last two minutes in a half and the team has one timeout left. If the challenge fails, the team loses a timeout. Calls that can be reviewed include scoring plays, pass completions, if a player is out of bounds, quarterback pass or fumble and if a player is down by contact. It can also be used to determine forward progress and number of players on the field.
In tennis, computer systems process the input of several video cameras to determine if a ball is in or out. Players can make up to three unsuccessful challenges per set, and a fourth in a tiebreak. Television broadcasts may use the footage to replay points even when not challenged by a player.