Chess clock

A chess clock is a device with two independent clocks and mechanism for ensuring that only one of them is running at a time. They are used for the game if chess (and other games such as Scrabble), to ensure that neither player overly delays the game.

The players must make a predetermined number of moves in a certain amount of time, depending on the nature of the game. In tournament play, for example, players are allotted approximately three minutes per move; high-profile championships allow longer time limits; local club matches and informal games allow shorter ones. A particularly popular variant in informal play is "speed" or "blitz" chess, in which each player is given five minutes on the clock for the entire game.

The players may take more or less time over any individual move, which means that whilst the start of the game is a relatively quick succession of moves, the players can spend a large period of time thinking over the more complex moves later. The players are permitted to leave the table during their opponents turn--but there is nothing stopping their opponent from deciding on their move and pressing the button to restart the opponent's clock.

Standard Time Controls

In tournament Chess, the most common time controls for professionals are at 40/2, SD/1 time controls which means that the first 40 moves must be made in two hours and then the remaining moves be made in an hour. Any extra time from the originally 2 hours carries over to the sudden death time.

In tournament Scrabble, the time control is standardized to 25 minutes per side with a 10 point penalty for each minute that is used in excess.

In tournament Shogi, players generally have a set limit for all of their moves and then the byoyomi rule goes into effect. When a player runs out of time, this will mean that all moves must be made in a set time limit. For example, in fairly fast games, a game will be played with 30 minutes per side with a 30 second byoyomi. This means each player will have 30 minutes for their moves and then after that they must make every move within 30 seconds.