The controversial line calling system Hawkeye was used for the first time in an elite-level tournament at the Hopman Cup on Friday and the shot tracker was called into play early in the opening contest.
As the Netherlands faced China in a playoff for a place in the eight-nation mixed team event, umpire Pascual Maria over-ruled a call in the third game but Dutchwoman Michaella Krajicek challenged and the replay supported the original decision.
Her opponent Shuai Peng then successfully challenged a call early in the second set but lost a subsequent appeal when the replay showed that a Krajicek serve had brushed the line.
The Hawkeye system, which had been tested for three years before being used in a seniors event in London recently, uses cameras to track the ball's trajectory.
Information is sent to a computer that generates a three dimensional animated image and the path of the ball is shown on large screens at the ends of the court.
However, rules have been put in place to prevent the system being abused, and the chair umpire can deny the challenge if it is thought the player is using it in an inappropriate or untimely manner.
The chair umpire also retains the right to make the final decision on a call.
Peng, who during the 2005 season claimed victories over Kim Clijsters and Elena Dementieva, was rewarded for her persistency when she put China ahead by overcoming the erratic Krajicek 6-3 4-6 6-3.
Half-sister of 1996 Wimbledon champion Richard, Krajicek often looked the better player, with her strong forehand and powerful double-handed backhand hit to the corners.
But she won only two of nine break points and struggled to find consistency. She produced 10 aces, including three in succession, but also 10 double-faults, and she crucially failed to convert a break point in the seventh game of the deciding set.
Two double-faults and finally a forehand error allowed Peng to break for 5-3 and the Chinese player successfully served out for the match.
The ITF-sanctioned event, now in it's 18th year, consists of eight teams split into two groups.
Group A is composed of Russia, the United States, Sweden and Serbia & Montenegro. The playoff winner will join Group B, which is made up of Argentina, Australia and Germany.
Teams compete in a round-robin format consisting of two singles and a mixed doubles, with the winning nation from each group progressing to next Friday's final.
