Data Transmission Modes: The term ‘transmission mode’ is used to define the direction of signal flow between two linked devices.
There are three ways or modes for transmitting data from one point to another. These are:
1. Simplex
2. Half-duplex
3. Full-duplex
1. Simplex: If the transmission is simplex, communication can take place in only one direction. Devices connected to such a circuit is either a send-only or a receive-only device. For example, broadcasting of signals to the television. In this case, TV can receive signals only, it cannot send back signals to satellite or any other device.
In data processing applications, communication in both directions is required. Even for a ‘one-way’ flow of information from a terminal to a computer, acknowledgement from the terminal to the computer is required. Thus, simplex circuits are seldom used in data communication.
2. Half-duplex: Signals can be transmitted from both sides but hot at a time. In halfduplex transmission, you can transmit signals in both directions, but not simultaneously. If the communication line is busy, then the message will be in a wait state. The buffer transmits that signal first, which is accepted first. Example of this kind of transmission is Email. When we send a message from our inbox to an Email address then the following message appears: Your message has been sent to the following recipient: chan- dress-5 @ Indiatimes. com. This is an acknowledgement, confirming that the message has reached to its recipient.
3. Full-duplex: Some applications require simultaneous transmission in both directions. In such cases, a full-duplex system is used that allows information to flow simultaneously in both directions on the transmission path. Examples of these transmission techniques are telephone system and signal transmission between different computer hardware devices. One common example of full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time.
