Ball Strikes FoxTenn Sensor

Last weekend in a semi-final match in Estoril, a ball in play struck one of the on-court sensors used by the electronic line calling system. Sebastian Korda delivered a shot that tipped the net cord and went almost straight up. Before it struck the ground, the ball came into contact with one of the black boxes installed at the bottom of the net that houses the FoxTenn sensors/cameras. That unlikely occurrence presents an interesting case study of the rules.

FoxTenn uses devices that are installed at the bottom of the net at each sideline for singles and doubles. The camera/sensor boxes are only installed on one side of the net . That makes a total of four of these sensors on the court. The boxes themselves are unobtrusive, but larger than you might think. The following picture is a closeup screen shot of the device that was struck during that match. The ball careened off in what can only be called a bad bounce, even by clay court standards.

Korda’s shot was called in and he was awarded the point. That prompted his opponent, Francis Tiafoe, to challenge the call. Chair umpire Richard Haigh indicated that a challenge was not possible because the FoxTenn system is unable to make a call when the ball strikes a sensor. Haigh further explained that examination of a mark was not possible since the ball hit the box rather than the court.

After that brief protest by Tiafoe, the ruling was accepted by both players and play resumed. Tiafoe was down 2-5 in the second set and had already fought off a match point when this unusual event transpired. Interestingly enough, Korda later expressed frustration at the length of the delay, even though the call went in his favor. (Tiafoe went on to win the match. )

The following image captures the approximate moment that the ball struck the sensor. The impact point seems to indicate that it was the correct call.

Or was it…

Interestingly enough, neither Tiafoe nor Haigh discussed whether the FoxTenn on-court sensors are permanent fixtures . The fact that the lines are painted on the top of the devices implies that they are a part of the court, but that is not explicitly stated. The lines could just as well be present for cosmetic or alignment purposes.

The ATP Rulebook calls out the FoxTenn system by name and there are provisions in the rules that outline how the chair umpire communicates with the operators of the system. The ATP Rulebook is silent on whether line calling sensors are permanent fixtures. I suspect that the 2023 ATP Rulebook may be more clear on that point.

As an interesting side note, the ATP net signage is explicitly considered to be a permanent fixture. That may strengthen the case for that the FoxTenn sensors might also be a permanent fixture.

Case: The ball, while in play, hits the top of the ATP net signage and goes into the proper court.
Decision: ATP net signage will be considered permanent fixtures (other than the net, posts, singles sticks, cord or metal cable, strap or band) and will result in the loss of point.

ATP Official Rulebook, VII.S excerpt

Tiafoe could have asked for an interpretation of tennis law from the chair umpire on whether or not the FoxTenn sensor was a permanent fixture. If he was dissatisfied with the answer he could have then summoned the referee to the court for a second and final authoritative decision.

If the FoxTenn sensor was determined to be a permanent fixture, then Tiafoe would have been awarded the point since Korda’s ball struck the device prior bouncing on the court.

It is an unusual situation.

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1. ATP Official Rulebook, 2022, ATP.
2. WTA Tour Official Rulebook, 2022, WTA.

(By sheer coincidence, Haigh is also the umpire in “Calling the Lines: Court Officials” where he is the subject of a YouTube video titled “Worst Overrule Ever.”)