Digital chess clock

A digital chess clock has two linked displays, with only one side running at a time. After making a move, the player presses their button to stop their display and start the opponent’s. That press normally turns the move into a completed move.

Its main advantage over a mechanical clock is precise programming of time controls, meaning how much time each player receives and how it is divided into periods. It also shows a digital clock flag when time expires and may display seconds, periods, and a press count.

Increment and delay

• Increment: a fixed amount of time is added before each move, including the first, according to the clock setting.
• Delay: each turn begins with a fixed interval during which the main time does not decrease. If the clock is pressed before that interval ends, the main time remains unchanged.

The clock follows its programmed setting, but it does not decide whether moves were legal. If a display, time, or move count appears wrong in a competition, the proper response is to pause the clock and ask the arbiter, the official who applies the rules, rather than reprogram it unilaterally.