Simplex, Half Duplex & Full Duplex

I was reading a book named Fundamentals of Telecommunications by John G Proakis and thought to share about the modes of channel operation.

Broadly there are three modes
1. Simplex
2. Half Duplex
3. Full Duplex or simply Duplex

Each suits to a particular purpose.

Simplex 

• One-way operation; there is no reply channel provided. 
• Ex. Radio and television broadcasting

Half Duplex 

• Two-way service. 
• Defined as transmission over a circuit capable of transmitting in either direction, but only in one direction at a time.
• Internet browsing is the best example where we send request first and then the content is loaded

Full Duplex/Duplex 

• Two-way service
• Defines simultaneous two-way independent transmission on a circuit in both directions. 
• Mobile communication is full duplex connection

An add-on illustration that i found somewhere on internet

GIF images credits - http://www.iec-usa.com/Browse05/DTHFDUP.html

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Satya Sravan