1. Functions: device, , voice intercom, , learning assistant, network time synchronization 2. Applications: clock, ID card, counter, memory game, talk, sports management, compass 3. Diversified wear: watch wear, arm wear, waist wear and hanging wear 4. Built in clock chip: it can be saved in case of power failure, and accurate timing 5. Rechargeable battery: Compared with button battery, it has capacity, long endurance, environmental protection and recyclable charging 6. Loaded speaker: Compared with the buzzer used in other audio circuits, it can play sound files and record and play 7. Programming platform: graphical programmer, Python language programmer 8. complete supporting materials and manuals, and devote to complete teaching solutions Product name: for : bit K-Watch (without board) Model: K-Watch Small Hole Diameter:2.0mm Power Supply:5V ( USB power supply ),3.7-4.2V ( 18650 Lithium battery ) Operating Voltage:3V / 5V Functions: Accurate time, data when power off ( based on DS1240 ) Network communication,intelligent control (connect to 2.4g hotspot) Intercom function (communicate between two boards should be 10m) Size:78 x 53 x 23mm color:Black+beige Material:PCB+metal Package Contents: 1 x K-Watch expansion board 1 x Lithium battery (with adhesive back) 1 x Watch strap 1 x Waist strap 1 x Screwpack+screwdriver 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.