LONDON -- If the play gets boring at the World Cup, watch out for the secret signals between the match officials running the game.

Although radio communications between the referee and his three assistants have been tested in top European competition this season, they will not be featured in Germany, although it appears inevitable they will soon play a part in elite soccer.

However, electronic devices are not the only way for match officials to communicate.

Over the years referees have developed discreet ways of passing or receiving messages, often involving the assistants helping out the man in the middle when he or she may not have seen an incident.

A player tumbles to the ground in the penalty area and the referee, his view of the play blocked by a crowd of players, looks quickly at the linesman. If he raises his flag to his chest briefly, then it's a penalty. If the linesman places his hand on his breast pocket -- where yellow and red cards are kept -- then he's recommending a yellow or red card.

The players have most probably not realized the assistant has given the decision and so do not charge at the linesman in fury, leaving the referee to take the flak, as is his duty.

Next example: The ball hits the crossbar, then bounces down. Did it cross the line? The assistant referee is best placed to see and the sight of him running back toward the halfway line for a restart tells the referee it's a goal.

If he stays where he is, then the ball has not crossed the line.

For years referees have run what they call a diagonal system to keep up with play, ensuring they are always looking across toward the linesman, with the run play in between. Now, however, as the game has sped up, referees are under instructions never to be more than 15 yards from play.

Sometimes, however, that's impossible and the linesman has to help out while the referee catches up. For those few moments -- and whenever he is closer to play than the referee -- the assistant has much more power than the spectator realizes.

At the elite level, the referee, unless he is absolutely convinced to the contrary, will accept the decision of the linesman faithfully. At the World Cup, the officials are a team, almost all from the same country, and a group that often officiates together in their national league, so they know and trust each other.

The latest trend in refereeing is for the 10-minute clampdown. Soccer games inevitably have flashpoints when the referee needs to be at his most alert and firm.

For the first 10 minutes of a match, especially if it's a grudge game, the referee will be tough on everything, blowing his whistle for every misdemeanor. As the game progresses and players settle down, the referee will also start allowing play to flow and speed up, ignoring some challenges. But when tension suddenly erupts, the 10-minute clampdown returns.

Look out in Germany for the referee holding his arm rigidly by his side with his fist clenched as he alerts his linesmen that they need to be on the same wavelength.

A few minutes later, as calm is gradually restored, the referee will make a similar signal with a rigid arm, only the fist is replaced with an open hand and the officials can relax a little.

While several other methods of communications exist between a referee and his linesmen, the most important remains eye contact. Every referee, in his prematch instructions to his co-workers, will stress how crucial it is for them to be looking at each other.

Ever wondered why it's not very often a referee points one way for a throw-in and the linesman points the other? Watch the hand of the linesman without the flag in it. If it's raised slightly, it's a signal for the referee to give the throw-in that way.

But the assistant will also be looking at the referee's left or right hand and will always opt for a majority decision rather than be seen to disagree with his boss.

It's also very rare that a referee does not see his linesman waving the flag. But if he doesn't, the final weapon in the assistant's armory is a button on the end of his flag which, when pressed, sets off a loud buzzer on a strap concealed under the referee's sleeve.

That's a surefire way of attracting the referee's attention.

Associated Press Writer Simon Haydon is a licensed referee in England and has been officiating games for five years.