Fire alarm, 'Hawk-Eye' system shutdown briefly halts play at U.S. Open

The U.S. Open is the biggest tennis event in the country but even it isn't immune from hiccups.

Monday afternoon, while several matches were in the middle of play, a fire alarm sounded at the building that houses the tournament's automated line calling system — dubbed "Hawk-Eye."

According to ESPN's broadcast, the building was evacuated and the "Hawk-Eye" shut down, resulting in chair umpires suspending play until the situation played out.

After a five to six minute delay, the alarm was turned off and staff allowed back into the building so matches could resume.

"Hawk-Eye" replaced human line officials at the U.S. Open in 2022 and according to CNBC , was invented in 1999 and acquired by Sony in 2011.

All tennis majors except the French Open use automated line calling, which is "millimeter accurate" Hawk-Eye Innovations director of tennis Ben Figueroa told CNBC.

Electric line calling goes back as far as the 1980s when Wimbledon trialed a system called "Cyclops" to judge calls on the grass surface.

It's unclear if the U.S. Open has back-up human line judges in the event the "Hawk-Eye" system goes down entirely or if Monday's episode persisted past a few minutes.