The Video Assistant Referee - or VAR - was set up for the first time in an English competitive game at the AMEX Stadium on Monday night for the FA Cup clash between Brighton and Crystal Palace.
Referee Andre Marriner was backed by assistant Neil Swarbrick, who was watching the game on television in the Premier League's west London studio.
They were able to use between 12 and 15 camera angles - plus four cameras in each goal - to try to ensure the right decision was made during Brighton's win over Palace.