Want to play audio from an MP3 player or smartphone through your car radio? Belkin has a solution. The Belkin F8Z439-P Tune Cast Auto Universal Hands-Free Auxiliary Transmitter Cable has 1 end that plugs into your car’s 12 volt accessory port to power it and 1 end that plugs into a 3. 5 mm aux port on your device for audio playback. It then uses smart-scanning technology to automatically locate the clearest FM station in your area then transmits your audio into the FM radio for playback through your car’s audio system. 2 programmable preset buttons on the Belkin Tune Cast Transmitter let you quickly find your saved stations. For a safe, hands-free way to listen to music through a car radio, choose the Belkin Tune Cast.