In soccer, you can wear a cap. Soccer laws enable a player to wear a hat as long as it fits the standards outlined in the Laws of the Game. During a soccer game, protective headgear, hats, and headscarves are all authorized. The only time a player is prohibited from wearing a helmet is if he or she is on the ground receiving medical attention. There are three types of helmets used by soccer players: goal-line technology, full face masks, and mouth guards. Goal-line technology uses sensors that detect when a ball has been kicked into the air near the goal line and sends a signal to the referee's booth alerting him to check for goals. Full face masks are worn by defensive players in order to protect their faces from foul plays directed at the opponent's players. Mouth guards are used by offensive players to protect their mouths while they're receiving balls during free kicks or corner kicks. Mouth guards are not required by law but are recommended by most coaches. Coaches may allow players to wear headbands as long as they are made of leather or synthetic material and do not contain any materials that could affect visibility such as silk or rayon. Headphones are allowed during soccer games but are not permitted during play. Hearing protection devices such as earplugs or headphones must be removed before entering an official soccer match.