FM support channel This Bluetooth Car FM Transmitter lets you enjoy your music phone while driving and has a louder, clearer phone than the car stereo navigation voice. Hands-free calling support The built-in microphone supports the hands-free Bluetooth phone, and only needs to press the button to answer the phone, which is convenient to use and ensure safe driving. Maximum 3.4A smart  Built-in dual USB port, up to 5 V / 3.1A output, smart charging dock, automatic identification of various mobile / tablet / MP3 / MP4, providing and output charging current in the best and fastest way. TF card / U music player disc Support TF card to read music, can play music files on MP3 / wma. (excluding TF card) Independent power switch The built-in power switch turns the transmitter on/off for one second, eliminating the need to connect or disconnect each time, preventing the battery from discharging and making it easier to use. Large LCD display The large screen can display the FM frequency and the name of the connected device. It also displays the song name and plays the time in TF card/USB flash drive mode. Support voltmeter function The screen shows the voltage when the car battery is lit. Rotating design The display rotates 80 degrees and is suitable for cigarette lighter plugs in different positions on most different models. Commonly used in various vehicles DC 12-24 V input voltage for most cars, trucks, off-road vehicles, etc.