Tennis: Technology poised to call all the shots: Tennis may be revolutionised by an electronic line-calling system which is being pioneered at the US Open starting on Monday. John Roberts reports

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A 23-stone linesman was banned from officiating at the United States Open last year because of his bulk. Now even flyweight judges are an endangered species as technology calls the shots.

The human element would have been reduced almost to the bones at this year's US Open, which starts on Monday, but for protests by the players. These prompted second thoughts by the organisers about relying solely on an electronic line- calling system installed on the four main courts.

Initially, the US Tennis Association intended to dispense with the customary 10 linesmen and use only an umpire and three judges, two for foot-faults and one for service net-cords. Instead, a full crew of linesmen will be on duty, if only to accompany the system's beeps with token gestures.

Technology will rule, except when a ball lands beyond the extensive range of the TEL (Tennis Electronic Lines) system. 'The decision of TEL will not be overruled under any circumstances,' stressed Brian Williams, managing director of the manufacturers. 'The linesmen are there as a compromise for the comfort of the players.'

This is the first occasion a major championship has not depended upon the accuracy of the human eye, and while some traditionalists will lament further diminution of the personality of the sport, critics of the power-dominated modern game might find it appropriate that robotic players are to compete on computerised courts.

TEL was tested during the men's over-35 event at the US Open last year and was also used on an experimental basis, with human line judges, in the over-45 competitions. Of 2,956 balls within 300mm (12 inches) of the lines, there were 301 instances of the electronic system disagreeing with the judges. If we accept the accuracy of the computer this means that more than 10 per cent of line calls were wrong.

The system is electromagnetic and is operated by the umpire with a hand-held computer. An instrument box, containing 13 computers, is placed next to the umpire's chair. Antennae beneath the court surface monitor an area 300mm wide each side of the lines. Metal particles embedded in the rubber core of the balls enable the antennae to start transmitting data when a ball is approximately four inches above the surface. The 'footprint' of a ball striking the surface produces an electronic signal. The system then records the ball's speed, angle and where the outer edge is in relation to the outside of the line.

TEL was developed in Australia, though this is not the reason why the players feared a kangaroo court. A Grand Slam tournament, they argued, is not the place for experimentation. 'I can't imagine why they should try it at the US Open,' Andre Agassi said. 'I would prefer them trying it out in other tournaments and seeing how players and people respond to it.'

Tim Mayotte, president of the ATP Tour's player council, wrote to the USTA objecting to the use of the system at Flushing Meadow. 'We do not question the accuracy of the TEL system,' Mark Miles, the ATP Tour's chief executive, said. 'What we don't know is how players' performances will be affected when exposed to it during match conditions and how tennis fans will respond. We have not yet seen adequate plans to train officials or procedures to deal with contingencies like system failure. The Tour and players believe the Challenger circuit is an appropriate level for introducing an electronic system.'

The Women's Tennis Association expressed similar misgivings. 'I think overall it's a great idea,' Martina Navratilova said. 'I just don't think trying it out at the US Open is such a hot idea. I don't know how well the umpires will be schooled in dealing with the system.'

A service line machine, 'Cyclops', has been in operation at major tournaments since it was introduced at Wimbledon in 1980. Players have tended to be ambivalent towards 'Cyclops', which occasionally beeps before they strike the ball. There have been times when suspicious competitors have persuaded an umpire to disconnect 'Cyclops' and there was John McEnroe's memorable reaction in a match at Madison Square Garden: 'I don't want to sound paranoid, but that machine knows who I am.'

McEnroe failed to unsettle an Australian umpire, Richard Ings, with a tirade at the US Open after 'Cyclops' failed to react to a serve which the official considered to be about 18 inches long, beyond the machine's range. 'We'd need a good back-up system and an early warning if anything went wrong with the technology,' Ings said. 'What would happen if the system failed in the middle of a match at a major tournament, with so much at stake and millions watching on television?'

Pete Sampras, whose serving won him the Wimbledon title in July, considers that 'machines take a lot of personality out of the game. People come to watch for the way players react to different situations.' An ATP Tour survey of 520 spectators at a tournament in Atlanta supported this view: 70 per cent said players should be permitted to object to line calls and a plurality of 47 per cent thought that an electronic system would make the game less enjoyable.

Navratilova disagrees. 'You still have the drama with the players out there,' she said. 'You don't need to add to it by questionable line calls. Nothing ruins a good tennis match more than bad line calling. Any time you can eliminate human error I think is a good thing.'

TEL point out that they have been 'shadowing' line-calling with the electronic system at tournaments since 1990. They maintain that the accuracy of the system is approximately five times better than can be achieved by the best line judges and that it is consistent over the whole court.

Their sales pitch contains impressive data: 'The speed of a ball when striking a court surface can be as high as 50 metres per second. At this speed a ball can cross a line in less than two milliseconds. The time a ball is in contact with the court surface can be less than five milliseconds and is rarely above ten milliseconds. The human eye cannot separate two events less than 15 to 20 milliseconds apart, as illustrated by the fact that a fluorescent light produces a series of flashes approximately 20 milliseconds apart, but, to the human eye, the light appears to be continuous. In 20 milliseconds a ball from a fast serve can approach a service line, contact the court surface, squash and skid 160mm and rebound 300mm. These details cannot be observed by a human line umpire, who must judge where the ball landed largely by observing the blurred images of the arrival and departure paths.'

The same applies to those other mere mortals, spectators and players, who may be inclined to dispute that TEL is infallible and that everything they see is an optical illusion.

It was intended to monitor line calling on the show courts at the Australian Open in January, but this was abandoned after rain seeped under the surface of Court Two while the electronic system was being installed and made it unplayable. TEL has been safely embedded in the concrete at Flushing Meadow for months and has been in use during qualifying matches this week.

The manufacturers say the system also can be installed in cushioned surfaces, clay and synthetic grass courts and that designs for indoor courts and natural grass are being developed. Wimbledon will follow the experiment at the US Open with interest, though there are no immediate plans to computerise the lawns.