The Decision Review System (DRS) in cricket explained

After an on-field decision, the batter or the fielding captain signals a review with a 'T'. The third umpire checks the replays and technology, then tells the on-field umpire whether to keep or overturn the decision. Markets usually suspend during the review.

DRS combines ball-tracking, which predicts the ball's path for LBW decisions, with edge detection such as UltraEdge, which uses sound to show whether the ball touched the bat. Slow-motion replays from several angles are used too, and some series add thermal imaging such as Hot Spot.

• Ball-tracking, which predicts the ball's path for LBW decisions.
• Edge detection such as UltraEdge, which uses sound to show whether the ball touched the bat.
• Slow-motion replays from several camera angles.
• Thermal imaging such as Hot Spot, in some series.

When ball-tracking shows the ball only clipping the stumps or the line, the evidence isn't strong enough to overturn the original decision. The on-field call stands, and the reviewing team doesn't lose its review. Bets settle on the final decision.

Markets are usually suspended while a review is in progress, then reopen once the decision is final. A wicket overturned by DRS can swing session and match prices sharply, so avoid trying to bet during a review. Wait for it to reopen.

Ball-tracking answers three questions in order. Did the ball pitch outside leg stump? If so, it can't be out. Did it hit the pad in line with the stumps, unless the batter offered no shot? Would it have hit the stumps? Only when all three point to out does the third umpire give it. Marginal answers to the last two fall into umpire's call.

Under ICC playing conditions, within 15 seconds of the on-field decision. That's why captains consult the bowler and keeper quickly. The batter or fielding captain signals with a T, and the third umpire then checks the technology before the on-field umpire confirms the final decision.

It was first trialled in a Test series between India and Sri Lanka in 2008, before becoming part of international playing conditions. Ball-tracking and sound-based edge detection now do most of the work. Reviews per innings are limited. Each side gets limited reviews.

Bettors should note that a team with no reviews left is more exposed to a wrong decision late in an innings, and that close LBW calls often end as umpire's call, so the original decision tends to stand. Markets settle on the final decision after any review, not the first on-field signal.

• A team with no reviews left is more exposed to a wrong decision late in an innings.
• Close LBW calls often end as umpire's call, so the original decision tends to stand.
• Markets settle on the final decision after any review, not the first on-field signal. See the betting rules.