Direction of Data Transmission

Besides the previously mentioned ways in which data may travel, there are three directional modes of travel in data transmission.

• Simplex Communication: Simplex communication is a mode in which data only flows in one direction. Because most modern communications require a two-way interchange of data and information, this mode of transmission is not as popular as it once was. However, one current usage of simplex communications in business involves certain point-of-sale terminals in which sales data is entered without a corresponding reply.

• Half-duplex Communication: Half-duplex communication adds an ability for a two-way flow of data between computer terminals. In this directional mode, data travels in two directions, but not simultaneously. Data can only move in one direction when data is not being received from the other direction. This mode is commonly used for linking computers together over telephone lines.

• Full-duplex Communication: The fastest directional mode of communication is full-duplex communication. Here, data is transmitted in both directions simultaneously on the same channel. Thus, this type of communication can be thought of as similar to automobile traffic on a two-lane road. Full-duplex communication is made possible by devices called multiplexers. Full-duplex communication is primarily limited to mainframe computers because of the expensive hardware required to support this directional mode.