With DC isolation, 5V power supply (4.5-5.5V) With DC isolated power supply: suitable for modifying speakers, power amplifiers, and car-mounted Bluetooth functions to solve common ground current noise and noise AUX audio input, Qualcomm 5.0, /ATPXHD, power on, default volume is maximum, amp chip, better sound quality KCOM is the common terminal of the button, the other end of the button is connected to +, -, PREV, , PLAY, and the length of the button cable is within 5cm Key Description: "+": short press to increase the volume, long press to continuously increase the volume "-": Short press to decrease the volume, long press to continuously decrease the volume "": short press the song "PREV": short press the previous song "PLAY": short press to play/pause, long press for 3 seconds to force into pairing mode, long press for 6 seconds to clear the pairing list The appearance and color of different batches , which does not affect the use Colour:black Material:PCB Package Contents: 1 x Module 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.