MH MX8 Module Wireless for Bluetooth Audio Receiver Board Lossless Decoder Kit M18 M28 M38(M38 with 5W Amplifier Type ) Item Type: Module Function / model M18 M28 M38 MICRO power supply No Yes Yes Audio headphone Interface No Yes No Built-in amplifier No No Yes(5W+5W) Lithium battery powered Yes Yes Yes Support USB sound card, free drive No No Yes Volume memory/adjustment Yes No No MUTE mute interface Yes No No Button extension Yes No No for Bluetooth version For Bluetooch V4.2 Support for Bluetooth protocol HFPV1.7, A2DPV1.2, AVRCPV1.5, AVCTPV1.2, AVDTPV1.2 Format support Support WAV/WMA/FLAC/APE/MP3 un-decoded, stereo two-channel output Operating Voltage 5V/3.7V-4.2V Not connected Broadcast state  5.5MA Connection work state 20MA Deep sleeping 3UA Transmission distance 20 meters (empty or low interference environment) Operating temperature -40C to +85°C Sensitivity -87dbm MH-M18: Number Pin Description 1 KEY Button control terminal (4 button functions, additional resistance required) 2 MUTE Mute control terminal (output high level 3.3V when muting, output low level during playback) 3 VCC Positive power supply 5V (lithium battery 3.7V power supply requires short circuit diode) 4 GND Negative power supply 5 L Left channel output 6 R Right channel output MH-M28:  Number Pin Description 1 5V Power positive 5V 2 GND Negative power supply 3 VBAT Lithium battery positive 3.7-4.2V 4 L Left channel output 5 R Right channel output 6 AGND Audio ground MH-M38: Number Pin Description 1 5V Power positive 5V 2 GND Negative power supply 3 VBAT Lithium battery positive 3.7-4.2V 4 L+/L- Left channel output (direct speaker) 5 R+/R- Right channel output (direct speaker) Blue Module: The light blinks when for Bluetooth is not connected The indicator light usually lights up when for Bluetooth is connected For Bluetooth appears during playback, slow flashing