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The Difference Between Full Duplex & Other Network Transmission Modes

Network administration courses used walkie-talkies vs. telephones as examples to explain the difference between half duplex vs. full duplex in how data is transmitted.

For years network administration courses used walkie-talkies and telephones as prime examples to explain the difference between half duplex vs. full duplex in how data is transmitted.

This is the point where a Millennial raises their hand and asks,”what’s a walkie-talkie!”

If you are old enough, however, to understand ‘over and out’, then the walkie-talkie/telephone analogy makes sense.

A half-duplex connection allows information to flow in only one direction at a time. Like a walkie-talkie, you can send or receive, but not both at once.

In a full-duplex connection information flows in both directions at the same time, like a telephone conversation.

There is a third mode, simplex, where data only flows in one direction.

Simplex: A One-Way Street

Traditional television and radio transmission modes are simplex examples with the signal travelling in only one direction.

Simplex fiber optic cables have only one fiber with one end the transmitter and the other end the receiver.

Modern examples of simplex transmission modes include garage door openers, baby monitors, and loudspeakers.

Simplex uses the full capacity of communication channels during transmission and has no data traffic issues as information flows only in one direction.

The downside is no back-and-forth communication between devices.

Half Duplex: Two-Way Traffic on a One-Way Street

In a half-duplex transmission, information can now travel in both directions, but only in one direction at a time.

If a network were half-duplex, it could only send or receive data, leaving one side to wait for an opening to transmit while an existing data stream was being received.

You could stream a video file over a half-duplex connection, but you could not carry on a phone or real-time conversation.

Half duplex has the advantage of being bi-directional but two-way communication cannot be established simultaneously. Delays in transmission may occur as communication can only go in one direction at a time.

Full Duplex: Two-Way Traffic All the Time

Full-Duplex is the bi-directional data transmission mode in which the data can flow in both directions at the same time.

This two-way communication is simultaneous and the fastest mode of sending data between devices as it eliminates the collisions and overheads associated with reversing half-duplex connections.

Another advantage of full duplex is that bandwidth is, in theory, doubled as data in both directions can take advantage of the connection.

For example, with a bandwidth of 10 Mbps, in full duplex each direction can achieve up to 10 Mbps at the same time for a total of 20 Mbps.

True doubling is rarely achieved, but the throughput is always greater in full duplex vs. half duplex.

Another bonus of full duplex is that upload and download rates are consistent—optimal for remote offices or cross-office collaboration.

Full duplex also eliminates virtually all data collision on properly configured network and results in fewer network bottlenecks.

For a network to flow at optimum speed all devices should be linked in the same mode. A mismatched duplex between a switch and a router or firewall, can cause packet loss in your network.

In the age of Zoom meetings and remote work, mismatched duplex can slow traffic to a crawl and kill voice quality.

Rise of Full Duplex

Full Duplex has been around since the first 19th century telephones and 100 years later the patent for the first cordless phone termed the device a “full duplex communications apparatus”.

In the early Internet days duplex fiber optic cables were created by joining two fibers together, with one strand transmitting in each direction for bi-directional movement. Later, single-strand duplex fiber, which can send data in both directions, emerged to fuel growth of full duplex networks.

As early as 1998, Cabling Installation and Maintenance magazine proclaimed: “No matter what the networking game, full-duplex transmission will be a winner. [IS] managers looking to leap into twenty-first century technology should give careful consideration to full-duplex networks.”

Today, all PS LIGHTWAVE services are exclusively full duplex. Our expansive all-fiber optic footprint across the Greater Houston can take full advantage of your 21st century technology.

Contact PS LIGHTWAVE today to find out how a full-duplex network can help grow your business.

PS LIGHTWAVE provides high-speed, fiber Internet for public and private commercial entities in the Greater Houston and surrounding areas.

Through our high-quality infrastructure, innovative technology and expert, locally based support, we deliver not only the best in connectivity and reliability but in scalability and redundancy. We invite you to learn more about our services, our history and our dedicated team.

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PS LIGHTWAVE, a leading telecommunications service provider headquartered in Houston, Texas, provides managed Ethernet Data Circuits, Internet, private network solutions and Voice over IP (VoIP) over one of the nation’s largest facilities-based private Metropolitan Area Networks (MANs). The switched Layer 2 network, backed by 24/7/365 Network Operations Center (NOC) support, encompasses approximately 5,500 route miles and 1,400 on-net locations and connects 100+ fault-tolerant multi-gigabit Ethernet rings for built-in redundancy, security, low latency, and high-availability. At PS LIGHTWAVE Great Connections Happen Here™.

For more information, please visit or call 832-615-8000.