Item Type: Module_x000D_ Function / modelM18M28M38_x000D_ MICRO power supplyNoYesYes_x000D_ Audio headphone InterfaceNoYesNo_x000D_ Built-in amplifierNoNoYes(5W+5W)_x000D_ Lithium battery poweredYesYesYes_x000D_ Support USB sound card, free driveNoNoYes_x000D_ Volume memory/adjustmentYesNoNo_x000D_ MUTE mute interfaceYesNoNo_x000D_ Button extensionYesNoNo_x000D_ for Bluetooth versionFor Bluetooch V4.2_x000D_ Support for Bluetooth protocolHFPV1.7, A2DPV1.2, AVRCPV1.5, AVCTPV1.2, AVDTPV1.2_x000D_ Format supportSupport WAV/WMA/FLAC/APE/MP3 un-decoded, stereo two-channel output_x000D_ Operating Voltage5V/3.7V-4.2V_x000D_ Not connected Broadcast state 5.5MA_x000D_ Connection work state20MA_x000D_ Deep sleeping3UA_x000D_ Transmission distance20 meters (empty or low interference environment)_x000D_ Operating temperature-40C to +85C_x000D_ Sensitivity-87dbm_x000D_ _x000D_ _x000D_ MH-M18:_x000D_ NumberPinDescription_x000D_ 1KEYButton control terminal (4 button functions, additional resistance required)_x000D_ 2MUTEMute control terminal (output high level 3.3V when muting, output low level during playback)_x000D_ 3VCCPositive power supply 5V (lithium battery 3.7V power supply requires short circuit diode)_x000D_ 4GNDNegative power supply_x000D_ 5LLeft channel output_x000D_ 6RRight channel output_x000D_ _x000D_ _x000D_ MH-M28: _x000D_ NumberPinDescription_x000D_ 15VPower positive 5V_x000D_ 2GNDNegative power supply_x000D_ 3VBATLithium battery positive 3.7-4.2V_x000D_ 4LLeft channel output_x000D_ 5RRight channel output_x000D_ 6AGNDAudio ground_x000D_ _x000D_ _x000D_ _x000D_ MH-M38:_x000D_ NumberPinDescription_x000D_ 15VPower positive 5V_x000D_ 2GNDNegative power supply_x000D_ 3VBATLithium battery positive 3.7-4.2V_x000D_ 4L+/L-Left channel output (direct speaker)_x000D_ 5R+/R-Right channel output (direct speaker)_x000D_ _x000D_ _x000D_ _x000D_ Blue Module:_x000D_ The light blinks when for Bluetooth is not connected_x000D_ The indicator light usually lights up when for Bluetooth is connected_x000D_ For Bluetooth appears during playback, slow flashing