Dual USB Port & Safe Charging: Features two USB charging ports to charge two devices simultaneously with overcharge protection for safer charging. Built-in smart chip automatically adjusts voltage based on device requirements. Hands-free Calling: Bluetooth 5.0 technology ensures fast pairing and stable signal transmission. Automatically reconnects to previously paired devices when powered on. Rotary button allows easy FM channel selection and control for play/pause, answering, and ending calls. Easy to Use: Plug the Bluetooth FM transmitter into the cars cigarette lighter socket. Tune the car radio to an unused FM frequency between 87.5 and 108 MHz, then set the transmitter to the same frequency. Pair the device with your phone or tablet via Bluetooth to play music or make hands-free calls. Wide Compatibility: Supports music playback via Bluetooth, TF card, and USB drive. Automatically detects and plays MP3, WMA, FLAC, WAV, and APE format files. Compatible with most smartphones, tablets, and other Bluetooth-enabled devices. Excellent Stereo Sound: Equipped with built-in noise-reducing microphone for clear full-duplex audio, enabling clear hands-free calls and navigation voice prompts. Provides clear and uninterrupted quality during use.