The way in which data is transmitted from one place to another is called data transmission mode.
Types of Transmission Modes
There are three types of data transmission modes:
1.Simplex Mode In simplex mode, data can flow only in one direction . It cannot be moved in both directions. It operates in a manner similar to a one-way street.The direction of flow never changes.A device with simplex mode can either send or receive data. It cannot perform both actions. An example is a traditional television broadcast. The signal is sent from the transmitter to TV antenna. There is no return signal.
2. Half - Duplex Traffic:
In half - duplex mode , data can flow in both directions but not at the same time. It is transmitted one - way at one time. A device with half- duplex mode can send or receive data but not at the same time.That is why the speed of half-duplex mode is slow.An example of half-duplex is a narrow bridge that can carry single vehicle at a time .The traffic from side A stops while the vehicles from side B cross the bridge. Similarly, traffic from side B has to stop so that the Vehicle from side A may cross.
3. Full-Duplex Mode
In full- duplex mode, data can travel in both directions simultaneously. Full duplex mode is a faster way of data transmission as compared to half duplex. Time is not wasted in changing the direction of data flow. A telephone is a full- duplex device . Both persons can talk at the same time.Another example of full- duplex communication is automobile traffic on a two- lane road.The traffic can move in both directions at the samwe time.
1.Simplex Mode 
