With DC isolation power supply: suitable for refitting speakers, power amplifiers, and vehicles to add Bluetooth function to solve common ground current sound and noise. AUX audio input, Qualcomm 5.0, APTX/ATPXHD(Please make sure that your mobile phone, Bluetooth headset, Bluetooth speaker, and Bluetooth audio device support ATPXHD, otherwise this function cannot be used and it will be automatically downgraded to APTX.), power on, the default volume is maximum. TI amp TPA6132A2, better sound quality. KCOM is the common end of the button, and the other end of the button is connected to VOL+, VOL-, PREV, NEXT, PLAY, and the button cord is within 5cm. Key Description: "VOL+": Short press to increase the volume, long press to increase the volume "VOL-": Short press to decrease the volume, long press to decrease the volume continuously "NEXT": short press a song "PREV": Short press the previous song "PLAY": Short press to play/pause, long press for 3 seconds to force enter pairing mode, long press for 6 seconds to clear the pairing list Style:A DC isolated 5V power supply (4.5-5.5V) Colour:green Material:PCB+Plastic+Metal Size:3.6 x 3.3CM Package Contents: 1 * QCC3031 Bluetooth Audio Module Only the above package content, other products are not included. Note: Light 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. With DC isolation power supply: suitable for refitting speakers, power amplifiers, and vehicles to add Bluetooth function to solve common ground current sound and noise. AUX audio input, Qualcomm 5.0, APTX/ATPXHD(Please make sure that your mobile phone, Bluetooth headset, Bluetooth speaker, and Bluetooth audio device support ATPXHD, otherwise this function cannot be used and it will be automatically downgraded to APTX.), power on, the default volume is maximum. TI amp TPA6132A2, better sound quality.