RDS also carries other data on the FM band - like the name of the song being played, or the weather information that is sometimes shown on some FM stations. The MIB unit (the module that lives in the glove box on a mk7 Golf) combines this information with the GPS data to locate the TMC data on the map that you see on the screen. Snala: So - as I understand for the SUNA service (here in Australia, at east), the actual TMC data is transmitted over the commercial FM radio - it uses a harmonic of the stereo sub-frequency in the RDS signal (I think).
