... built in, 1G / 2G /4G optional.2) Built-in FM wireless transmitter, transmitting range: 87.5MHz ~ 108.0MHz,total206 frequencies optional.3 ... format music in the built-in Flash memory,transmits music signal over car FM tuner, then enjoys music via car stereo ... frequency directly. Car MP3 Player T88 (car mp3 player with wireless fm transmitter/car mp3 transmitter) (GF-T88)