Amplifier board size: 5.7x3.3CM CSR8675 supports , -LL, ATPX-HD Power on, the default volume is maximum, just listen to music 3.6-5.5V power supply (compatible with lithium battery power supply or 5V power supply) VCC and GND are power supply pins, L, G, R are connected to the earphone DCOM is the common terminal of the indicator light, and the other end of the indicator light is connected to LED0 and LED1 respectively. KCOM is the common terminal of the button, and the other end of the button is connected to VOL+, VOL-, PREV, NEXT, PLY respectively Key Description: "VOL+": short to increase the volume, long to continuously increase the volume "VOL-": Short to decrease the volume, long to continuously decrease the volume "NEXT": short song "PREV": short the previous song "PLY": short to play/pause/answer/hang up, long for 1 second to reject incoming calls Special function description: "PLY": long for 3 seconds to force into pairing mode, long for 6 seconds to clear the pairing list Colour:blue Material:PCB Package Contents: 1 x Decoder 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.