The game is administered by two umpires whose duties are to enforce the rules as written in the current rule book. The umpires will blow the whistle and then use hand signs to signal their ruling.
The field hockey umpire's equipment includes a whistle, a 2-inch ring to check the legality of the sticks, and umpire cards. There are three cards, green, yellow, and red, which are used for misconduct violations. The green card is used for warnings, the yellow card is used to remove a player from the game for a minimum of five minutes, and the red card disqualifies the player from the game.
Understanding the hand signals of the umpire makes the game more enjoyable for the spectators. The following diagram shows a few of the hand signals used by the umpire during the game.
Umpires' Hand Signals