A referee raised a phone-sized electronic device to caution a player during a ?Uruguayan cup match this week, replacing the familiar flash of ?a yellow card with a digital screen ?in ?a trial aimed at modernising one of football's oldest rituals. Match official Eduardo Varela used the device during Nacional's Copa Uruguay match against Rentistas on Thursday, testing a system designed to simplify referees' ?administrative work by recording disciplinary decisions digitally."We are looking to bring technology to the only thing in football that is still analogue," said Mauro Sacco, director of REFe, the company behind the project, in an interview…