(EN) The invention inter alia relates to a data transmission system comprising a transmitting and/or receiving unit (120) on the track side and a transmitting and/or receiving unit (10) on the vehicle side. According to an embodiment of the invention, the transmitting and/or receiving unit on the vehicle side comprises at least one transmitting and/or receiving element (20-26) on the vehicle side which is mounted in the region of a track vehicle door (30), said unit being covered by the same and separated from the rail track (110) when the track vehicle door is closed and remaining uncovered by the same when the track vehicle door is open.