A sensor system developed in Germany has successfully completed a series of trials at tournaments on the men's international circuit, starting with the grass-court event in Halle in June and culminating at last week's ATP Tour Championship in Frankfurt.
Alan Mills, the Wimbledon referee, declared the system to have "worked beautifully" when officiating at the Eurocard Open in Essen recently.
Small sensors are placed at each end of the net and a cable is fitted to a hand control operated by the umpire, who presses a button when the server tosses the ball and releases it after the ball has crossed the net. A beep sounds if the ball touches the net cord.
Devised and manufactured by the Brauer brothers, who moved from east Germany to the Black Forest region, the machine has been fostered for the past two years by their compatriot Rudi Berger, one of the world's leading umpires.
The system is called Trinity, Berger explained, because of the three parties it was designed to help: "The umpire, the players, and somebody else who sits at the net and gets hurt."
Monitoring a net cord can be a high-risk pastime, especially when serves timed at up to 137mph induce reflex returns of a similar velocity. Helmets were used at the United States Open last year, but obviating the need for a person to put his or her neck on the line is a preferred option.
The absence of a human presence at the net has raised not the slightest protest from the players during the experiments conducted so far. "When the machine beeps the players seem to accept that the ball has made contact with the net cord," Berger said. "They don't raise their hands to show that the ball was at least a foot above the net, like they used to."
Wimbledon and the three other Grand Slam tournaments are showing a keen interest in Trinity, which could become as commonplace as Cyclops, the "magic eye" service-line machine invented 15 years ago by a Briton, Bill Carlton.
Cyclops, while prone to phantom beeps if the control button is pressed at the wrong moment, has prevailed, although John McEnroe once said to an umpire, "I don't want to sound paranoid, but that machine knows who I am."
Berger emphasised that Trinity's bleep is not as loud as Cyclops's and that the tone is different. "We wouldn't want any similarity. The players might become very upset if they heard a sound which reminded them that they had just served a fault."
Not all technological innovations have proved successful. TEL, an electronic line-calling system, was abandoned on the eve of the 1993 United States Open after metal objects caused the device to beep.
Player pressure persuaded officials to revise their original plan to use a skeleton crew of only three judges with an umpire on the four wired courts instead of the customary 10. One of the trinity would have monitored service net cords.