When data flows in one direction at a time, it is known as _______. The channel of communications allows alternating transmission in two directions, but not in both directions simultaneously. Two-way radios, such as police or emergency communications mobile radios, work with ______ transmissions. When you press the button on the microphone to transmit, you cannot hear the person on the other end. If people at both ends try to talk at the same time, neither transmission gets through.