How does it work?
Human line judges call each shot in a tennis match and players to have a limited
number of challenges available to them. The current rules allow 3 “incorrect”
challenges per player per set and an additional 1 if the play moves on to the tie-
break. Players must challenge a particular point in a timely manner. This includes
the stopping of the current point, approaching the net or indicating the chair umpire
that the player wishes to challenge the call.
Above: Alexander Zverev indicating the chair he wishes to challenge the call
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