BT5.0 Audio PRO continues the excellent basic functions of M28 (long-distance transmission, Bluetooth 5.0 backward compatible, lossless sound quality, etc.), and adds more user-friendly performanceCharge while putting: This product has a circuit of charging and discharging, which can directly charge the battery through the USB power supply, and Bluetooth can continue to work normally during the charging process, and truly realize the function of charging and discharging. Solve the pain point that some products can not be used during the charging process.When powered by USB alone: The red light flashes, indicating that the power supply is normal. When powered by a separate battery: The yellow light is always on, indicating that the battery power supply is normal; the yellow light flashes, indicating that the battery is low.When the USB and battery are connected at the same time: The red light flashes to indicate that the battery is charging; the red light always indicates that the battery is fully charged.(Note that if the USB input is suddenly disconnected during the charging and discharging process, there will be a few seconds of interruption due to the charge and discharge mode switching at this time, after which Bluetooth will automatically restart, automatically connect and maintain the previous playback state) Incoming voice call function: After the Bluetooth is connected, turn on the call audio mode in the Bluetooth settings.If the phone calls, you can answer or hang up the phone through the PLAY/STOP button. You can choose to send from the microphone of the headset (provided that the headset has a call function, which is a 4-segment type) or from the onboard microphone (default)Bluetooth version: Bluetooch V5.0Decoding format: HFPV1.7, A2DPV1.2, AVRCPV1.5, AVCTPV1.2AVDTPV1.2POWER IN: 3.7V-5V DCSignal to noise ratio :90DBApplication: MP3/MP4 PlayerType: Voltage RegulatorModel Number: BT5.0 MP3 PRO Bluetooth Audio Receiver boardTotal harmonic distortion: -70dBCrosstalk: -86DBSupport configuration file :HFP/A2DP/AVRCP/AVCTPV/AVDTPVTransmission distance :15MDecoding format: WAV+APE+FLAC+MP3Colour:blackMaterial:ABS+ plateSize:42.85 x 39.8 x 16.76mmPackage Contents:5 x Bluetooth Audio Receiver(Without battery)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.