American Jamea Jackson created tennis history on Wednesday when she became the first player to challenge a line call using Hawk-Eye technology.
Jackson went on to beat Harkleroad 7-5 6-7 (3-7) 7-5
The system has been introduced on the men's and women's tours for the first time at this week's Nasdaq-100 Open.
Jackson used one of her two allowed challenges to question a call of "out" in her match against Ashley Harkleroad.
A close-up of Jackson's shot and the word "OUT" was flashed onto a large screen, confirming the call.
"I loved it, I thought it was great," Jackson said afterwards. "It takes a lot of pressure off.
"You don't get angry. You just play and don't worry about the line calls. I wanted to be the first (to use the system), that's what it was really all about."
Hawk-Eye has been tested at other events but is making its tour debut at the ATP and WTA tournament in Miami.
This year's US Open will be the first Grand Slam event to feature the system but every tournament, including Wimbledon, now has an option to use it.
Under the new rules:
- Each player will receive two challenges per set to review line calls.
- If the player is correct with a challenge, then the player retains the same number of challenges.
- If the player is incorrect with a challenge, then one of the challenges is lost.
- During a tie-break game in any set, each player will receive one additional challenge.
- Challenges may not be carried over from one set to another.