[Hands-free car kit] The built-in microphone will automatically switch from playing music to hands-free calling when answering a call. Answer/hang up/reject/redial calls or activate Siri/Google Now by clicking the multi-function button. [Dual USB ports and QC3.0 fast charging] The Bluetooth radio frequency modulation transmitter has 2 USB ports for charging. QC3.0 fast charging interface is 5V/3A, charging speed is 4 times faster than traditional car charger. The other USB interface is 5V/1A, which can read music files in the U disk, such as MP3, WMA, WAV format. [3 music playback modes] Support Bluetooth playback, microSD card playback (maximum 32GB), U disk playback (maximum 32GB). Note: To avoid any noise, please remember to adjust the frequency of the fm transmitter to be the same as the frequency on the car radio (choose a blank radio station to avoid signal interference)[Crystal clear sound] The latest Bluetooth V5.0 car radio adapter and CVC noise reduction technology ensure that the fm transmitter can be connected to your device faster and more stably, bringing you CD-like sound quality. [LED voltmeter display and 7-color light change] When the FM transmitter is inserted into the car cigarette lighter, the car voltage will be displayed. Thanks to the memory function, the last paired mobile phone can be automatically connected. In addition, the colorful LED lights can switch between 7 different colors or enter the breathing lighting mode.