Yep, it's a bit like TCP/IP, each packet of data is addressed, it just picks out the ones it wants. There are several other ways of sharing one transmitter. CDMA,TDMA,PDMA,DAMA,FDM.<br /><br />On a different note,<br />In the case of different frequencies on the same transponder, it's just like an FM radio. If you think of the whole FM band as one transponder, then the radio just tunes to the signal it wants.