Now make your Car SMART with this all-in-one Roboster Bluetooth FM Car chargr What you can do with this car bluetooth fm transmitter? Fm transmitting Adjust this bluetooth fm transmitter for car to the same frequency with car audio, music from cell phone or TF card can be played through car audio. Handsfree calling When cell phone matched with the bluetooth fm transmitter car kit, hands-free talking will be realized, which can improve driving safety effeciently. Type C Car phone Chargng Type C usb ports for your convenince. Two phones can be CHG.d at the same time with two usb ports, the maximum output is 2.1A. Aux input 3.5mm aux input is supported, connect your phone or mp3 with the audio cable to transfer voices to the device, then to the car stereo Note: Audio cable need to be linked to the external audio device first, and then insert into Audio input socket, otherwise it will not play music of the device. Car Battery Voltage/ Overcurrent Display car battery voltage display mode: The switch to the U / I, car battery voltage display. (Voltage display range: 9-30V, over range display HHH; error ± 1V) Load current display mode: The switch to the U / I, insert the load, the load current display. (Load current is less than 0.13A does not display error ± 0.1A) Technical Parameters Rated working voltage: 12V-24V USB output: 5V/2.1A Play format: MP3 Battery voltage display accuracy Error: ±1V Load current accuracy Error: ±0.1A Frequency response: 20Hz-15Khz Resolution of right and left channel >60dB Bluetooth version Version: 3.0 Bluetooth sound processing A2DP function supported Bluetooth transmission distance: 10M Effective distance of Bluetooth microphone: 0.5-2M FM frequency: 87.5~108Mhz Package include: 1x Bluetooth car chargr.