Smart QC 3.0 quick charging: The Bluetooth car transmitter has dual USB ports and can charge two devices at the same time. One is a QC 3.0 USB port for quickly charging, 4 x faster than standard chargers. (Compatible with: QC2.0, HUAWEI FCP, Samsung and HTC). At maximum power, the charging efficiency is more than 80%, so your device can be fully charged in a short time. Bluetooth hands-free system: Advanced Bluetooth 5.0 technology allows for a more stable connection and faster transmission. The built-in high-performance microphone with CVC noise reduction technology offers you a crystal clear hands-free function after connecting via Bluetooth. With just one touch of a button you can easily set up answer / end / reject / call the last number functions. Drive safer. Multi-music playback mode: Enjoy lossless stereo music transmission. The FM transmitter can play your favourite music from Bluetooth devices via FM signals to car radios. A USB stick can be used to transfer and play MP3 / WMA songs. This Bluetooth FM transmitter offers you wonderful car music and makes your journey more fun. Easy operation: Plug this Bluetooth FM transmitter into the cigarette lighter socket. Turn on the cars FM radio and select an empty frequency. Then set the frequency to the FM transmitter (87.5 - 108.0 MHz). Connect your phone to the transmitter (name as C57) via Bluetooth. With a wider frequency from 87.5 MHz to 108.0 MHz, you can get a more stable and consistent music experience without interference. Multiple protection and wide compatibility: comes with built-in smart IC, over current protection, over voltage protection, intelligent temperature control and short circuit protection. This car Bluetooth FM transmitter can be paired as a hands-free kit with any Bluetooth device for iPhone, iPad, iPod, Tablet, Samsung, HTC, Sony and other Android smartphones. Built-in microphone with CVC technology for clear conversation. Wirelessly transfer music as FM signal to the car stereo. A music USB port for connecting a USB flash drive (max. Capacity 64 GB). A USB port for charging QC 3.0 and quickly charges the phone. LED Display: Displays FM frequency and battery voltage. Provide hands-free function and a safe driving experience. Multi-music playback modes:Music playback via Bluetooth enabled device or USB stick, excellent built-in microphone with echo cancellation noise reduction (CVC) technology, enjoy lossless stereo music transmission when driving. Bluetooth hands-free kit:With more stable FM signal, built-in microphone with echo cancellation noise reduction (CVC) technology, this FM transmitter allows you to talk clearly. Drive safely. Smart QC 3.0 Quick Charge:Bluetooth car transmitter has dual USB ports and can charge two devices at the same time. One is QC 3.0 USB port for fast charging, 4x faster than standard chargers. This will fully charge your phone at high speed. How to use:Plug the Bluetooth FM transmitter into the cigarette lighter. Then this FM transmitter automatically turns on and shows the voltage of the car battery. Then you can easily know the car battery condition. 1.12 V means that the battery must be replaced. 2.12.0-12.8V will indicate the normal voltage if the car does not start. 3.13.0-14.8V will indicate the normal voltage when the car is started. Note: If the voltage when starting the vehicle is less than 12V, replace the battery as soon as possible. How to reduce static interference when playing music? Please understand that when using the FM transmitter in certain situations, static interference may occur. Please take the following steps to fix the problem. 1.Please try with another "clean" radio frequency. 2.Please adjust the volume of the car speaker, normally 40% is enough. 3.Please make sure the volume of your phone is maximum. How to adjust the volume? The volume of the car speaker, usually 40% is enough, not exceed 60%. The volume of the FM transmitter could reach 2/3 or 4/5. But please do not try to reach the most volume. The volume of the mobile phone could reach 2/3 or more.