Wireless Bluetooth FM Transmitter Car Kit Radio Receiver with 5V/2.1A USB Charger output Support USB Flash Driver and Micro SD Card AUX output and inputUsing FM Transmitter function:1. Plug the FM transmitter into your vehicle's cigarette lighter or power port.Tune your radio to an unused FM frequency, then match the same frequency of this unit.2. Insert a USB flash drive or SD card which containing MP3 files into USB port or memory card slot of this unit accordingly. It will play and transmit the MP3 files automatically.3. Line-in function: Use the provided audio cable to connect an MP3/MP4 players or another external device to the AUX input of this unit. When using this function, please stop playback of USB or memory card, and all functions will be controlled by the external device.Using Bluetooth function:Using Bluetooth for the first time, you need to pair your mobile phone with this unit. Activate your mobile phone\'s bluetooth function, then search new device. When the mobile phone detects this unit, please pair and connect by using the password \""0000\""In the music playing mode, when there is an incoming call, this unit will automatically switch to telephone mode.