WASHINGTON -- From the vantage point of the broadcast booth, there was little doubt about what was going on during changeovers of a third-round match at the Australian Open last January. TV cameras captured a player repeatedly reaching into his racket bag to use a BlackBerry-type device at the same time his coach, looking on from the stands, was captured on TV using his own BlackBerry-type device. After tournament officials were informed about the behavior, which smacked of a violation of the sport's ban on coaching during matches, the chair umpire ordered the player in question, Dudi Sela, to stop. Sela, who lost in four sets, told reporters afterward that he had only been trying to turn off his vibrating phone. But he was fined $1,500 for unsportsmanlike conduct -- in this case, according to Australian Open referee Wayne McKewen, using his mobile phone during a match -- and didn't appeal. It was never established that Sela's coach texted tactical advice. But if so, it would hardly have been the first time the sport's coaching ban was flouted. It simply would have represented the latest technological twist on an age-old ruse. Coaching is an integral part of nearly all stick-and-ball sports. NFL coaches bark elaborate instructions into quarterbacks' headsets from the first snap to the last. NBA coaches are celebrated for drawing up buzzer-beating plays. And caddies advise on club selection. But coaching has traditionally been banned in professional tennis -- a sport, at its essence, that pits one athlete against another in a test of skill, fitness, mental resolve and tactical guile. "It's part of the beauty of the sport," says former world No. 1 Jim Courier, who was in the broadcast booth for Sela's match in Melbourne. "The lack of coaching on court makes tennis unique, and it's something we should guard." But as the line between sports and entertainment has blurred in tennis, so, too, has the stance on coaching. Both the men's and women's tours have experimented with limited coaching during matches and, in some instances, broadcast the advice given. At the moment, coaching is banned in the men's game and in all matches at the four majors -- Wimbledon and the Australian, French and U.S. Opens. But it's allowed on the women's tour, as well as in Davis Cup competition and World TeamTennis. Veteran coach Nick Bollettieri, who has nurtured such champions as Andre Agassi and Maria Sharapova, can make a case for and against it. "Some say (coaching) takes away from the thought process and limits whether or not the player can make decisions for themselves," Bollettieri says. "On the other hand, if you're able to do some constructive coaching at times of difficulty, that might help the player get through it when they have to do it on their own." Bollettieri, for one, isn't ashamed to say he has taken liberties with the rules -- sometimes signaling advice by removing his sunglasses at a critical juncture; other times by scratching his head. At the French Open years ago, Bollettieri says he gave one of his pupils an index card listing several gestures and the corresponding tactic he wanted her to employ for each. But when she looked up at him for the signal during the first changeover, he realized he had forgotten to put his own copy of the index card in his shirt pocket. "I'd forgotten the card!" Bollettieri says, laughing. "So for the whole match, I never moved a muscle!" Policing the line between general encouragement that's acceptable ("Keep after him!") and specific advice that's not ("Attack his backhand!") can be difficult. Todd Martin remembers an exhausting five-set match at the U.S. Open years ago against a Spaniard whose coach sat directly behind the chair umpire and out of his line of sight so he could discreetly give advice in Spanish during changeovers. After falling behind two sets to none, Martin called for the supervisor of officials, who told him he couldn't do anything about it. So Martin asked him to sit beside his opponent's coach. The advice stopped. And after the momentum turned in Martin's favor in the final set, his opponent blurted out in Spanish, "Give me back my hands!" "You can't put duct tape over a coach's mouth and handcuffs around his wrists," Martin says. "You also can't ask them all to encourage their players in English. But it has to be monitored by the umpire and by the supervisor and referees, as well."