Smart QC 3.0 fast charging]:The Bluetooth FM transmitter has two USB ports to charge two devices at the same time. One of them is a QC 3.0 USB port for fast charging, 4 times faster than a standard charger. (Compatible with: QC 2.0, FCP Huawei, Samsung and HTC.) At maximum power, charging efficiency exceeds 80%, so your device can be fully charged in no time. [Passive Bluetooth]:Advanced Bluetooth 4.2 technology provides a more stable connection and faster transmission. When connected to Bluetooth, the built-in microphone with CVC noise reduction technology provides you with clear hands-free calls. Accept/end/reject calls/set last call with the press of a button. Drive in complete safety. Multiple music playback modes Enjoy lossless stereo music transmission. Allowing you to play music via Bluetooth/USB Key (64G)/TF Card (64G) connection, this Bluetooth FM transmitter will provide more stereo and dual channel sound with its high fidelity system. It supports MP3/WMA/WAV/FLAC/APE format files. It gives you great car music to make your trip more enjoyable. Easy to use]:- Plug it into the cigarette lighter socket. Turn on your car's FM radio and select the empty frequency. Set the same frequency as the transmitter (87.5-108.0MHz). - Connect your mobile phone to the transmitter (called C57) via Bluetooth.You can then listen to music without interference. The multi-protection Bluetooth FM transmitter is equipped with over-current protection, over-voltage protection, short-circuit protection and intelligent temperature control.