Four video assistant referees (VAR) will be present during every game at the 2018 FIFA World Cup in Russia with replays to be displayed on the giant screens inside the stadiums, FIFA said.
"Everything will be centralised in a single location in Moscow and all referees will be based in Moscow," explained FIFA's referees' chief Pierluigi Collina during a training seminar organised at Coverciano, near Florence.
Two groups of 36 referees and 63 assistants will be trained over the next two weeks for the World Cup, with workshops being organised on the VAR system which is set to be used for the first time.
Former Italian referee Roberto Rosetti explained how VAR system would work during the mega event.
"There will be four VAR officials. The VAR principal will communicate with the main referee and can suggest that he comes to verify images on the sidelines," explained Rosetti.
"The VAR assistant number one will be in charge of following the match live while the review is taking place. VAR assistant number two will be specially in charge of off-side."
Whereas to watch out for off-side players, two specially-adapted cameras will be used during the World Cup.
There will be four additional technicians in charge of screens and camera angles, with a FIFA representative ready to pass on the decisions with explanations on giant screens.
"We have to remember that the the very clear objective and the success of VAR will also depend on how it is understood," said Collina.
"It's about avoiding clear and obvious major errors. It's not a question of refereeing the match with technology. The goal has never been to check every minor incident."