Important Note: How to Adjust FM Frequency from Transmitter: 1.The calling button is a multifunctional button,please press the calling button at first to enter frequency mode 2.And then rotate the calling button to adjust fm frequency. Bluetooth-compatible 5.0: Advanced Bluetooth-compatible 5.0 technology, Faster and more stable than BT4.1 or BT4.0. Our Bluetooth FM transmitter is capable of streaming wonderful music and keeping you connected when you are driving. Supoort Music Format: WMA,APE,FLAC,WAV Hands-free Calling: It is built-in Mic with Echo Cancellation and Noise Suppression (CVC) technology offer you a clear talking. Just one click when receiving a call, the Bluetooth FM transmitter will provide you with the hands-free function and safer driving experience. Mutil Play Mode Support TF card and U disk extended playback,noise and wind suppressed by CVC technology will create full duplex sound quality, lets you enjoy the lossless music whilst driving. Dual Ports Charger: Support charge both devices simultaneously, Smart output current pairs all cellphone and tablet, safely charging to your device without damage to the battery. Battery Voltage: Automatically detect car battery voltage, voice reminder, support instant voltage viewing. Specifications: 1. Working voltage: 12V-24V 2.USB output voltage: DC/5V 3. Dual USB :5V/3.1A (Max),2.1A+1.0A 4. Version: Bluetooth 5.0 5. Effective distance: 0-8M 6. Launch distance: 0-3M 7. Support TF card / U disk capacity: 64GB 8. Voltage detection range: 6-30V 9. Power mode: cigarette lighter power supply 10. Bit rate: 64-320KBPS 11. Harmonic distortion: