This tutorial explains the difference between simplex, half-duplex, and full-duplex. Learn what the data transmission modes are and how they are used.
A data transmission mode describes how two devices in a network communicate or exchange data. It specifics the direction in which signals travel over the media and the number of signals that can traverse the media at any given time.
There are three types of transmission modes. These types are Simplex, Half-duplex, and Full-duplex. Let's discuss these methods in detail.
Simplex is also called one-way or unidirectional. It allows communication in one direction only. Since signals travel in only one direction, the sender device uses the entire communication channel or all available bandwidth. The receiver device only receives signals. The receiver can't reply to the sender by using the same communication channel. TV remotes, garage door openers, and smart speakers are some examples of Simplex.
You can use the remote to control TV programs and functions, but you can't use the TV to control the remote in any way.
Half-duplex allows communication in both directions but not at the same time. Signals travel in both directions over a medium but in one direction only at a time. Since signals travel in only one direction, a device can either send or receive data at a given time. A network card set to Half-duplex cannot receive data when it is sending data. To receive data, it needs to change the direction of data flow. To change direction, a special signal is used and acknowledged. The time required to turn over control to the other side is called the line turnaround time.
Railway tracks and walkie-talkies are examples of half-duplex. Only one train can run on a railway track at a time. If a train is on the track, the second train has to wait until the first train leaves the track.
Full-duplex is also called two-way or bidirectional. It allows communication in both directions simultaneously. It divides the available channel into two parts and uses one part to send data and the other part to receive data. Since there is a separate path for sending and receiving data, a device can simultaneously perform both tasks at a given time.
A two-lane highway is an example of a full-duplex. A two-lane highway uses dedicated lanes for incoming and outgoing traffic.
A network interface card can operate in both half-duplex mode and full-duplex mode. All modern NICs run in full-duplex mode. Some older NICs only support half-duplex. Auto-sensing is a feature that allows a NIC to automatically detect whether the remote NIC supports full-duplex.
| Simplex | Half-duplex | Full-duplex |
| It provides one-way communication. | It provides two-way communication but one way at a time. | It provides two-way communication at the same time. |
| A device can only send data, but it cannot receive data. | A device can send and receive data but one at a time. | A device can send and receive data at the same time. |
| It utilizes less bandwidth than half-duplex and full-duplex. | It utilizes more bandwidth than simplex but less than full-duplex. | It utilizes more bandwidth than simplex and half-duplex. |
| It uses one channel to transmit data. | It also uses one channel to transmit data. | It uses two separate channels to transmit data. |
| Keyboards and scanners are examples of simplex. | Hubs and old NICs are examples of half-duplex. | Switches and modern NICs are examples of full-duplex. |
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