Simplex transmission: data can travel in only one direction
Example: a traditional TV broadcast, in which the signal is sent from the transmitter to your TV antenna
Half-duplex transmission: data travels in both directions but only in one direction at a time
Example: Police radio, in which both parties must take turns talking
Full-duplex transmission: data is transmitted back and forth at the same time
Example: Telephone talking and listening simultaneously, in a software that support truly interactive collaboration using products like Ms. NetMeeting