General description BT5.0 Audio PRO continues the excellent basic functions of M28, including long-distance transmission, Bluetooth 5.0 backward compatibility, and lossless sound quality. It features a user-friendly design that allows for charging while in use, solving the common issue of devices being unusable during charging. Technical specifications Bluetooth version: V5.0 Decoding formats: HFPV1.7, A2DPV1.2, AVRCPV1.5, AVCTPV1.2, AVDTPV1.2 Input voltage: 3.7V-5V DC Signal to noise ratio: 90dB Harmonic distortion: -70dB Crosstalk: -86dB Transmission distance: 15m Supported audio formats: WAV, APE, FLAC, MP3 Size: 42.85 x 39.8 x 16.76mm Material: ABS + plate Color: Black Package Contents 10 x Bluetooth Audio Receiver (without battery) Usage To use the incoming voice call function, connect via Bluetooth and enable call audio mode in the Bluetooth settings. You can answer or end calls using the PLAY/STOP button. Choose to use the headset microphone (if it has a call function) or the