Bluetooth FM transmitter built-in 10 functions: This device Receive Mobile’s Calls, Music, Google/Apple Maps Navigation Voice via Bluetooth and Wireless transmit the audio into carFM radio;Bluetooth Receive Mobile’s Calls, Music, Google/Apple Maps Navigation Voice via Bluetooth;Wired Receive audio signal from Mobile; MP3/MP4 Player; CD/DVD player via cable then FM transmit this audio into car FM radio; Play Micro SD Card’s Audio file and Wireless transmit the audio into car FM radio;Play Micro SD Card’s Audio file, then wired transmit the audio to the car stereo via cable.Play USB flash drive’s Audio file, then wireless transmit the audio to car FM radio;Play USB flash drive’s Audio file then wired transmit the audio to car FM radio;Dual USB charging port:5V/2.1A smart and faster Car USB charger for all portable devices;5V/ 1A Car USB charger (Same with the USB flash drive port) for all compatible devices such as mobileCar Voltage Measurement while the kit plugging in the Car socket.On/off switch function, press and hold multi-function button 5 seconds to active sleeping function if you do not use it (car charging function still work at this mode)Using Tips:Press and hold the multi-functional button for 8-10 seconds to shift languages (English or Chinese);Methods of eliminating noise:Try to turn the mobile’s volume at maximum position, then adjust the car audio volume, the car maximum volume is not recommended. (this will bring lot noise).Connect a Ground Loop Noise Isolator before the car Aux-in port.Remove it after using it.Bluetooth FM transmitter built-in 10 functions: This device Receive Mobile’s Calls, Music, Google/Apple Maps Navigation Voice via Bluetooth and Wireless transmit the audio into car