Instant replay, which makes its Grand Slam debut at the U.S. Open today, is no longer the endless source of controversy that it once was.

After a full summer of challenged calls, there have been no tirades by players, linespersons, or chair umpires, no curses or damnations of its very existence. We have yet to see a ball so obviously out that was deemed good, or vice versa. The rhythm of matches is not upset. A few times, a chair umpire had to announce that the array of cameras that digitally map the court had been blocked or otherwise disturbed, and could not be used for a point in question. Even the players who objected to its use, Roger Federer chief among them, have either grudgingly (or happily) accepted their two challenges a set, plus a third in the event of a tiebreaker.

“If it’s there, it’s there,” Federer said. “If it’s not, it’s not. I don’t mind it anymore.”

For Jay Snyder, a chair umpire for 26 years and the former tournament director at the U.S. Open, the painless incorporation of instant replay into tennis’s repertoire is a source of amusement. Near the end of his umpiring career, Snyder witnessed the U.S. Open’s last experiment with instant replay, in 1992. It was a disaster.

The first replay technology went by the name TEL, for tennis electronic lines, and was manufactured by an Australian company (TEL Pty Ltd.). Installation proved a bit more cumbersome than the cameras of today. Engineers had to dig trenches the length of the court, on both sides of the lines. Wires were laid down, and then the trenches filled. The court was resurfaced.Wilson had to change its balls, too, blending iron filings into the rubber beneath the fuzz, while carefully subtracting the right amount of rubber to maintain the proper weight.A computer at the other end of the wires measured the velocity and trajectory of an incoming, iron-filing ball, and instantly signaled — via a red light, a beep, or a robotic call of “Ow-oooot!”— the chair umpire that a ball had landed, in accordance with the laws of physics, out of bounds.

“The system was really designed to replace the line umpires,” Snyder said this weekend. He was sitting in the bowels of Arthur Ashe Stadium, in a room behind the press center where ventilation systems and gears hum and clatter, the sort of place where old chairs are discarded and recycling is carted. The perfect place to reminisce about a technological failure.

The TEL experiment began in 1991. A year later, the U.S. Open used it during its qualifying tournament and hoped to rely on it, without any line umpires, during its senior event.

From the beginning, Snyder said,”We started getting all these stray beeps.”

The players were to blame.Several of them wore K-Swiss sneakers, still a popular brand of tennis shoes. In 1992, KSwiss fitted its shoes with metal eyelets, or rings, around the lace holes.The metal threw TEL for a loop.

Snyder said the manufacturer suggested banning K-Swiss shoes — an impossible solution. The experiment was put on hold until the senior’s event.More beeps occurred for various reasons, including knee braces and Bob Lutz’s racket, whose composition was not to TEL’s liking. In a match played on the Grandstand without line umpires, Ilie Nastase, the comedic and demonstrative Romanian, walked over to an empty sideline umpire’s chair and began to argue with it about an errant call, Snyder said.

TEL tried again at the 1993 Australian Open, but rain seeped into the trenches before they were properly sealed.The second-most important court at the tournament began to bubble up and could not be used for the second week, Snyder said. That was the end of instant replay.

Snyder still has fond memories of TEL. The problem, he said, was that it was rushed into action, rather than debated, tested on television, and then tested at tournaments, as was the current Hawk-Eye system, which is owned by the Television Corporation, based in England, and claims to measure the ball’s place of landing within three millimeters. Snyder said today’s umpires are not threatened by Hawk-Eye.

“We’re getting calls right,” he said. “I think that a substantial part of the umpires would like to see an unlimited challenge system. But there would be so much gamesmanship possible with that.”

At this weekend’s conclusion of the U.S. Open Series (11 tournaments), players had made 839 challenges and succeeded on 327 of them, a rate of 39%. Men averaged 3.2 challenges a match and were correct 41% of the time; women averaged 2.3 a match and were correct 36% of the time.

Perhaps the most interesting aspect for casual fans, however, is having a digital representation of what “in” means in tennis: any part of the line, even a glancing blow.

“If it’s 99% out, it’s 100% in,” Snyder said. At last, he can say this with certainty.

tperrotta@nysun.com