The data flow between the two devices can be in simplex, half-duplex, and full-duplex modes.Simplex:In Simplex, communication is unidirectional. Only one of the devices sends the data and the other one only receives the data.The channel capacity is used by only one device all the time.Example: A CPU sends data while a monitor only receives data. Half Duplex:In half-duplex, both the stations can transmit as well as receive but not at the same time. When one device is sending others can only receive and vice-versaThe channel capacity is shared by both the devices but at a time only once the device uses the full capacity.Example: A walkie-talkie Full Duplex:In Full-duplex mode, both stations can transmit and receive at the same time.The channel capacity is shared by both communicating devices at all times.Example: Mobile phones