Ethernet Video Series

Episode 02, Segment 03 of 03

Ethernet Evolved (continued)


To do that, they invented what we call an "Adapting Ethernet Hub" that has an old-style connector on one side, and a new style of connectors on the other side. It clipped into a coaxial segment like this...

(Click on above image for enlarged view)

A few years ago, if you had purchased an Ethernet hub, it would have looked like this, with two different styles of Ethernet connectors – one for the collision domain on a coaxial cable, and others for these newer, higher-speed cables that are more convenient and less expensive. This kind of configuration actually became quite popular with mixtures of the old-style Ethernet and their old connectors, and the new style, where the collisions could occur either on the coaxial cable or on a small collision domain segment, inside this little hub.

Once these collision segments were reduced in size from several hundred feet down to just a few inches, engineers were able to detect and manage collisions, even if the data rates were far greater. At that point, Ethernet speeds really took off, and we began to hear about 100 megabit per second - “Fast Ethernet,” - and later even - “Gigabit Ethernet". Eventually they started building these little hubs with clever circuits so that you could disconnect and remove the old-style coax, and the more modern connectors would still work, and where all of the collisions were occurring within a small little collision domain or Ethernet segment inside the box.

Over a period of a few years, the coaxial cable style of Ethernet gradually disappeared, and it became more and more commonplace to see these new kinds of networks where you just have an arrangement of new, more modern, less expensive Ethernet cable. You could think of these hub devices as just a little short collision domain with connectors, allowing a kind of fan-out, and you can learn a lot more about this kind of equipment elsewhere here on

Dual-mode hubs facilitated a gradual migration of connector types from the round BNC coaxial to the modern, keyed square RJ45 twisted pair-style. Of course, every kind of Ethernet-compatible equipment had to make the same transitions during those same transition years. Desktop computers became equipped with dual-mode, or even triple mode Ethernet adaptors. These are often called “Network Interface Cards,” (N I C), and sometimes the word is abbreviated as “NIC.”

(Click above image for enlarged view)

Here’s an example of a network interface card that adapts one computer's Ethernet interface to any of three different connector styles. (The D-shaped connector in the middle is an even older style that predates everything we’ve discussed.) For most users today, you will just identify the keyed rectangular connector using twisted pair, RJ45 cables that look a lot like fat telephone wires, and you’ll just ignore the other connector types, because they are relics of a by-gone day.

End of Episode 02. Continue with Episode 03.

Episode 03, Segment 01 of 04