FM TRANSMITTERCar FM transmitter will allow you to stream music from an external device such as a smartphone, tablet or other bluetooth device directly to the car radio. You can also play music stored on a Pen Drive or TF card by connecting them directly to the device. We can also access the functions of Siri / Google assistant and answer / reject callsBATTERY VOLTAGEThe bluetooth 5.0 adapter with USB for the car cigarette lighter socket (12/24V) has a screen that shows the battery voltage in real time, as well as an icon that shows the bluetooth status ( pairing/pairing) and the chosen FM frequency. It is very easy to install and adjust.FAST CHARGING USB PORTSThe bluetooth car mp3 player has different input and output ports: one QC 3.0 fast charging USB port, one USB port for Pen Drive/U disk input to play music, one USB port Type C PD fast charging and an SD card reading slot. The device can automatically change the playback mode when inserting the USB or SD card, also by pressing and holding the M button we can switch between modesHANDS-FREE FUNCTIONThe hands-free function is easy to use, we only need to pair the mobile with the device. By pressing the central wheel once we can answer calls, twice in a row to hang up, if we leave it pressed while we have an incoming call, we can reject the call.UNIVERSAL COMPATIBILITYThe cigarette lighter fm transmitter has universal compatibility with all vehicles with a 12/24V cigarette lighter as well as smartphones, tablets and bluetooth devices. It is a quick, easy and cheap way to have a hands-free and a music player in any vehicle