Product description Features: 1.Transmit the music from TF card to U disk to car stereo via FM signal. 2.Transmit the music of your Bluetooth enabled smart device to car stereo via FM signal. 3.Transmit music to car stereo via 3.5mm AUX port. 4. Answer phone calls during driving. 5. Two USB ports for charging devices, one of which can read U disk. 6. It supports IOS Siri voice software. Specifications FM Frequency: 88.1MHz - 107.9MHZ Product Input: 12-24V USB Charger Output: 5V/2.1A (Max) Read U-disk (max capacity): 32GB Read TF card (max capacity): 32GB Audio Input: 3.5mm stereo jack FM operating distance: 16.4ft NOTE 1.The transmitter will connect to the pre-set phone automatically when turns on. (Keep mobile phone’s Bluetooth activate). 2. For the best audio quality, please turn the volume of the cell phone and FM transmitter into the max level. 3. For the best sound quality, please tune it to an unused frequency; if there is interference when listening to music, please tune to another frequency. 4. The transmitter will power off automatically without any operation in 5 minutes, you need to press the multi-function button for 2 seconds to turn it on. 5. Do not dismantle the product.