2 USB Ports & Safe Charging: Supports charging two devices simultaneously with overcharge protection. One USB port with a music icon (5V/1A) supports USB disk reading, and the other USB charging port (5V/2.4A) efficiently charges your smart device. Enjoy in-car stereo streaming while charging your smartphone. 3 Music Playback Modes: This car FM transmitter allows clear stereo music playback through three methods: A. Bluetooth connection; B. USB flash drive (up to 32GB); C. TF card (up to 32GB). Supports MP3, WMA, FLAC, WAV, and APE audio formats. Ambient Blue Ring Light: When powered on, the blue ambient ring light illuminates, providing visibility in dark environments and enhancing the in-car atmosphere. The LED display shows volume level, car voltage, and FM frequency for easy viewing. Hands-free Calling: Equipped with a built-in microphone and features echo cancellation and noise suppression (CVC) technology for clear hands-free calls. Answer, reject, end, or redial calls with a single multi-function button. Automatically switches from music playback to hands-free mode when a call is received. Wide Compatibility: Compatible with iPhone, iPad, Samsung, HTC, Sony, tablets, and other Bluetooth-enabled devices such as MP3 and MP4 players. Works with all cars and trucks operating on 12-24V electrical systems.