History

• First adopted in a very limited capacity in 1986, the instant replay system began in earnest in 1999. It allowed coaches to challenge on-the-field calls by throwing a red flag onto the field before the next snap.
  
  

Replays

• Each team is allowed two instant replays per game. If both of the first two challenges are successful, a team is awarded a third instant replay.
  
  

Time Frame

• A play may be challenged by a coach at any time during a game, except within the last two minutes of the second quarter and the fourth quarter. At these times, challenges are issued by the officials.
  
  

Function

• Once a play is challenged, a referee has 60 seconds to watch the replay. A call can only be overturned if the referee sees "incontrovertible visual evidence" of the correct call.
  
  

Features

• If the call is overturned, the ball may be moved and/or time may be added or removed from the game clock. If a call is not overturned, the game resumes from the previous spot, and the challenging team is charged with one time out.
  
  

Types

• Challenges can be used on scoring plays, pass completions, out-of-bounds plays, forward passed, fumbles, down-by-contact plays, forward progress plays, touching of a kick and placement of the football.
  
  

Fun Fact

• Challenges used to be called by coaches through a vibrating pager linked to an official. Since 2004, red flags are used by coaches and pagers are used by officials in the booths within the 2-minute warnings.