Chess clock

A chess clock is a device that comprises two adjacent clocks with buttons to stop one clock while starting the other, so that the two clocks never run simultaneously. The clocks are used in games where the time is allocated between two parties. The purpose is to keep track of the total time each party takes and prevent delays. Parties may take more or less time over any individual move.

Chess clocks were first used extensively in tournament chess, beginning with a competition at the London 1883 tournament. They are often called game clocks, as their use has since spread to tournament Scrabble, shogi, Go, and nearly every competitive two-player board game, as well as other types of games. Various designs exist for chess clocks and different methods of time control may be employed on the clocks, with "sudden death" being the simplest.