Hands-Free KitInsert the FM bluetooth transmitter car to your car cigarette lighter, it will open the FM function automatically. Through press/rotate the multi-function button, can achieve answer calling/hang up calling, switch last song/next song, adjust volume up/volume down. Turn the knob to change music, and turn a lot to decrease / increase the volume.Multi-Ports & MultifunctionBuilt-in smart IC chip, the FM transmitter max support 3.4A current output. It support Android and iOS system. The two USB ports are for charging, but the port with the music symbol does not charge the tablet, it supports external USB (32G) and automatically power-off memory function. It can also read TF card.Show Car Voltage & FM FrequencyThe FM transmitter for car can detect the car voltage and show in the LED screen 1-2 seconds when it insert to the car cigarette lighter. After 1-2 seconds, it will show FM frequency. It will show FM frequency when you adjust it.Intelligent Distribute Charging CurrentAdopt intelligent chip, can change charging current according to device's electricity saturation, without damaging the battery, more secure. It also have over-charge protection, over voltage protection, over current protectiom, over load protection, etc, protect car and device's safety.