Function: This chess clock are 42 timing rules in 8 categories, including single/multiple countdown, reward, time limit, delay, seconds, and forward timing. Timing parameters can be changed for each timing rule(except positive timing). Different timing parameters can be set on the left and right sides. During the race, the timing parameters of both sides can be changed.<br> Portable and Durable: The digital chess clock is made of electronic components and ABS shell, environmentally friendly and durable, which is lightweight and portable, convenient for carrying.<br> Large Seesaw Button: Feel good, quick response, convenient control, more suitable for fast chess. Simple and intuitive to operate, comprehensive design to make your chess playing more enjoyable .The toggle button on top is easy to access and accurate, bright button color scheme indicates whose turn it is.Large LED display easy to read the time , non-slip pads at the bottom prevent accidental moves.<br> Keep Parameters: Power back on after power off, you can keep the rules and parameters of the race before power off. DC 3V power supply (two No. 5 batteries are not included).