This kit uses 3 separate two-digit digital tubes to display the time of hours, minutes and seconds respectively, and uses two small LEDs instead of colons for intervals, making the display of hours and seconds less compact and more natural. In addition to displaying time, it also expands the time calibration function, alarm bell function, countdown function, stopwatch function, and counter function. The realization of the function is mainly through programming and controlling the single-chip microcomputer, and using the internal timer of the single-chip microcomputer for timing. The kit is moderately difficult to make and highly practical. It can improve the understanding of the 51 series single-chip microcomputer and is suitable for electronic beginners to learn and practice welding. Note: This product is a DIY kit, not a final product! This soldering project requires basic electronics knowledge and hands-on skills. It is DIY kit Only. That is to say, all items are not welded on the pcb board. buyers have to weld them on the pcb board by themselves. Power supply voltage: DC5-12V Maximum operating current: about 5V 41mA, 9V 75mA, 12V 75mA (when the buzzer alarms) The printing/appearance may vary from batch to batch, but it will not affect the use; the actual product may have color difference due to different light or display. It's DIY kits, needs to finish by yourself. Colour:Green Material:PCB+Components Package Contents: 1 x DIY Kits Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.