[Product Description]: The answerer can perform 4-way priority answering at the same time. When a button is pressed the buzzer sounds. At the same time the number of priority answerers is displayed on the digital tube. After successful answering the display will not change by pressing other keys. Until the reset key is pressed the display clears at which time the next round of rush answer can be carried out. [Presupposition]:Please read the product instructions carefully and compare the parts and component list which can be obtained from customer service. Remember to attach your order number or full name of the product to avoid confusing the instructions. Manufacturered by DDIY. [Applicable Crowd]:1. Student of circuit and electronic soldering 2. Interested in soldering and assembly 3. Strong hands-on ability 4. Experienced in solderingetc. [Warning]:This product needs to be soldered by yourself. If you have no soldering experience please read the soldering instructions and use soldering tools carefully in order to avoid safety problems.If you need instructions or have any questions about the product please consult customer service. [Product Parameters] 1. Working Voltage: DC 5v 2.Size dimension: : 60MM*70MM 3. PCB Material: 1.6mm RF-4 Plate 4. Installation: DIY welding assembly 5. Type: Logic ICs Operating 6. Temperature: -30-85.