Use of a full duplex line improves efficiency as the

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Unformatted text preview: smitted. 2. A medium, which carries the message. 3. A receive (sink), which receives the message. For example, when you speak to your friend on the telephone, you are the sender. The telephone line through which your voice is transmitted is the medium and your friend is the receiver. This is a simple example of voice communication. The same concept holds good for data communication also. Data communication is the function of transporting data from one point to another. In this case, the sender and the receiver are normally machines, in particular, computer devices (computers, terminals, peripheral devices like line printers, plotters, disks, etc.) and the transmission medium may be telephone lines, microwave links, satellite links, etc. However, the messages that are transmitted are data, not voice conversations. Thus, the electronic systems that transfer data from one point to another are called data communication systems. Unlike computers that process and rearrange data, data communication systems transmit data from one point to another without any change. DATA TRANSMISSION MODES There are three ways, or modes, of transmitting data from one point to another. As shown in Figure 17.2, the; are simplex, half-duplex, and full-duplex. Simplex If transmission is simplex, communication can take place in only one direction. Devices connected to such a circuit are either a send-only or a receive-only device. For example, a data collection terminal on a factory floor (send only) or a line printer (receive only). At first thought, that might appear adequate for many types of applications in which flow of information is unidirectional. However, in almost all data processing applications, communication in both directions is required. Even for a "one-way" flow of information from a terminal to a computer, the system will be designed to allow the computer to signal the terminal that data has been received. Without this capability, the remote user might enter data and never know that it was not received by the computer (due to some problem somewhere). Hence, simplex ci...
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This document was uploaded on 04/07/2014.

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