Line position function: (button + 12V power line) Black line (key LED light negative control) Yellow line (positive trigger output control of key switch) 3-wire function description: + Positive trigger output control. After pressing the start button, the yellow wire outputs + 12V power; the black wire is connected to the key lamp to control the negative output wire, and the key lamp lights. Product Specification: Type Car Engine Start Stop Button Fitment Only for DC 12V models colour: black Material ABS size: 53.8mm x 10mm Package Contents: 20x Engine Start Stop Button 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.