The Caliber PMT557BT turns your car radio into a hands-free car kit. This transmitter connects to your smartphone via Bluetooth and wirelessly sends signals to your radio via a free FM transmitter. After installation you call hands-free via the built-in microphone and you hear your conversation partner over the speakers of your car radio. The transmitter is also a godsend if you want to listen to your own songs, but the radio has few connections. The design has inputs for aux and usb cables, usb sticks and SD cards. If you connect a smartphone or iPad via the second USB port, they are automatically charged.