The FM transmitter allows to play music from a microSD card, from a USB memory device or from a mobile device (using a line-in cable or via Bluetooth). The USB socket of the transmitter can also be used as a car charger. Its maximum current is 2.1 A. Thanks to the built-in microphone, the transmitter will also serve as a hands-free set. FM transmission frequency: 87.5-108 Mhz MicroSD card reading: up to 32 GB USB mass storage reading: up to 32 GB Bluetooth transmission range: up to 5 meters FM transmission range: up to 2 meters Effective microphone range: up to 2 meters