Mechanical chess clock

A mechanical chess clock combines two dials and two timing mechanisms. When a player presses the clock, their side stops and the opponent’s starts, so only one mechanism runs at a time.

Each dial uses a physical flag or equivalent device to show that a period has expired. Technical standards require a clear indicator, a non-glare surface, and quiet controls.

Unlike a digital clock, a purely mechanical model normally cannot add automatic increments, which add time after each move, or apply programmed delays, which postpone the use of the main time. It also usually cannot display an electronic press count. The time control, meaning the rule that sets how much time each player receives, must fit what the mechanism can represent.

The handling rules remain the same: make the board move first and press the clock afterward, using the same hand that moved. The clock technology does not change the one-hand rule.