STEREO MUSICUnlike other cheaper models on the market, our TYKEVO car FM transmitter will allow you to stream stereo music from an external device such as a smartphone, tablet or other Bluetooth device directly to your car radio. You can also play music stored on a Pen Drive or TF card by connecting them directly to the device. Also you can access Siri/Google Assistant functions and answer/refuse calls BATTERY VOLTAGE The USB bluetooth 5.0 adapter for the car cigarette lighter socket (12/24V) has a screen that displays the battery voltage in real time, as well as an icon that indicates the Bluetooth status (pairing/paired) and the chosen FM frequency. It is very easy to install and adjust. Includes instructions in French QUICK CHARGING USB PORT The car mp3 player has different input and output ports: QC 3.0 fast charging USB port, USB port for Pen Drive to play music, Type-C PD fast charging port and a micro SD reading slot. The device can automatically change the play mode when inserting the USB or SD card, also by pressing and holding the "M" button we can switch between modes HANDS-FREE FUNCTION The hands-free function is easy to use, just pair the mobile with the device. By pressing the central dial once we can answer calls, twice in succession to hang up, if we leave it pressed while we have an incoming call we can reject the call. If we press twice (without an incoming call) it will call the last number and if we leave it pressed we will access Siri or the Google voice assistant IMPROVES SOUND QUALITY Attention, this device is a transmitter FM, so it is necessary to have a radio in the car. The sound quality will largely depend on the FM frequency chosen. The cleaner and freer the station is, the cleaner and clearer the sound will be. Continue reading below in the description the section on how to improve sound quality. The advice detailed there can resolve the vast majority of problems.