Referees have been wearing armband radio receivers which emit a bleep when activated by a button on the shaft of each linesman's flag. The armband also vibrates to act as a signal when the referee is unable to hear the bleep over the noise of the crowd.
The optional extra for referees has been used in Swiss League matches for the last two seasons. "This is an invaluable help during moves when the referee has his back to the linesmen, when the bench is trying to make a substitution, or when a linesman wishes to attract his attention to something which has happened behind his back," a Uefa spokesman said yesterday.
Meanwhile, Uefa has denied that it has ordered a referees' clampdown at the tournament - despite the large number of yellow cards so far. Uefa's spokesman added: "Officials have only received two printed sheets of technical instructions, much of which is devoted to details such as the provision of drinks to players during matches.
"The Uefa referees' committee stresses that, in a tournament lasting a whole month, the important thing is to apply the laws of the game as uniformly as possible.
"However, the instructions urge referees to be strict with players who push or hold back opponents, in penalising fouls which could cause injuries and in penalising with a free-kick and a red card violent tackles which offer no opportunity to play the ball.
"Euro 96 referees are also urged to caution players who feign a foul, especially inside the penalty area. Clear cases of diving will be punished with a yellow card." Jurgen Klinsmann had better rethink his goal celebration routine.