1. Analog output (RP, RN, LP, LN), I2S output (BCK, LRCK, DATA), SPDIF output (DATA) 2. Function keys: KEYCOM, PLAY, VOL+, VOL -, PREV, NEXT, high level 3.3V is valid. Key functions are described as follows: PLAY: play/pause (short press); Re pair (long press 2.5S); Clear pairing list (long press 5S) VOL+: volume increase (short press, long press and continuous volume increase) VOL-: Volume decrease (short press, long press, continuous volume decrease) PREV: Previous song (short press) NEXT: Next song (short press) KEYCOM: key common terminal LED lamp: in pairing state, two lamps flash alternately; Pair successfully, single lamp flashes Always paired when there is no connection, no standby Control the mute pin MUTE of the external power amplifier (with sound: output high 3.3V) Support decoding format: Single output: support SBC/AAC/APTX/APTXLL Dual output: support SBC/AAC/APTX/APTXLL Single output with prompt tone, some external DACs do not play prompt tone, but do not affect music playing; Dual output without prompt tone Note:due to different production batches, the appearance printing is different, which does not affect the use. Specification:A:Analog Single Output/B:SPDIF Single Output/C:I2S Single Output Colour:As Shown Material:Plastic<br><br>Package Contents: 1 * Audio 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 picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.