- Integrate handsfree calls, Bluetooth FM transmitter, USB charger and MP3 player. Support hands-free phone calling via its built-in microphone. Built-in FM transmitter, 87.5-108MHz of full frequency. Built in microphone allows you to speak to callers without picking up the phone. CVC technology for noise and wind suppression, full duplex sound quality. Mobile phone can be connected automatically when the device turns on. With 3.5mm AUX jack, support line in and line out. Offers two 5V-2.1A USB ports for cellphone and tablet charging. Well positioned buttons for quick music and call control, volume adjustment knob. Support MP3/WMA music format. Screen display, easy operation.