It is a AD584JH reference voltage board. It can be used to calibrate the multimeter. It uses the copper terminal,and the multimeter pen can be inserted directly. It can select the output voltage value through the short-circuit cap. The input power can use the power of the router and plug it directly into the DC socket. Parameter: 1).Product Name:AD584JH Reference Voltage Board 2).Input Voltage:DC 12V-24V 3).Output Voltage:DC 2.5V/5V/7.5V/10V 4).Work Temperature:-25~85 5).Work Humidity:5%~95%RH Instructions for use: Input the DC 12V-24V voltage on the left side, you can connect it from the terminal, or you can directly use the router power supply to insert the DC socket, and use the multimeter test lead to insert it directly on the right side. If you can't insert it, adjust the screw. Just plug the shorting cap into the corresponding jumper. Depending on the batch, the color of the jump cap on the board is random, don't accept the specified, and the number written on the board may be different, but it does not affect the use. Colour:green Material:PCB Size:45 x 35 x 15mm Package Contents: 1 x AD584JH Reference Voltage Board 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.