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What Is an Ethernet Coupler?

An Ethernet coupler is a simple, yet essential device that connects two Ethernet cables together, extending the reach of a wired network. It's a cost-effective solution for seamlessly linking cables without sacrificing signal quality. Think of it as a bridge that unites distant devices. Ready to see how an Ethernet coupler can enhance your home or office network?
Carol Luther
Carol Luther

Ethernet cables connect computers, routers, modems and peripherals such as printers to networks and Ethernet communications boards. The cables carry signals that allow one to transfer data over a local or wide-area network. Ethernet couplers are plastic or metal connectors that one places between two Ethernets. The coupler allows one to join cables together and make a longer cable. This computer accessory makes it unnecessary for one to open an Ethernet cable and expose the wiring so it can be spliced into a second cable.

A standard Ethernet coupler is a small rectangular box that is open at both ends. The design allows the signal from the cable that one attaches at either end to travel to the cable that one inserts at the opposite side. Inside each open side of the Ethernet coupler are the appropriate wires that match those on the cable.

Cat 5 cable with RJ45 plug.
Cat 5 cable with RJ45 plug.

An Ethernet coupler has colored-coded wires inside the open end of the coupler box. When one properly inserts the end of an Ethernet cable that has connectors covered with a plastic sheath, the cable can make contact with the wires inside the coupler box. A coupler box also has a notch that matches a flexible tab on the sheath of the cable. This notch allows one to secure the cable and prevents inserting the cable incorrectly. To complete the coupling, one inserts the second Ethernet cable into the opposite end of the coupler box.

Ethernet cables are usually used to establish physical connections to routers.
Ethernet cables are usually used to establish physical connections to routers.

Before one purchases an Ethernet coupler, it is necessary to determine the type of Ethernet cable with which it will connect. The most common classes of Ethernet cables used by consumers are Cat 5, Cat 5e, Cat 6 and Cat 6a. Each of these cables has a different data transmission rate. These cables normally have their classification printed on their protective exterior sheath.

Cat 6 cables have backward compatibility with Cat 5 cables but, ideally, one should match cable types and couplers when connecting Ethernet cables. Retailers of Ethernet couplers have specifications that match Cat 5 or Cat 6 cables. Using an Ethernet coupler with an incorrect rating can result in data transmission signal loss or failure between the network card and the device to which one attached it.

The maximum length, including any Ethernet coupler used in the configuration, is different for each cable class. The upper limit for Cat 5 cables is 328 feet (100 meters). For Cat 6 cables, the maximum recommended cable length is the same; in mixed network wiring configurations, however, the recommended length drops to 180 feet (55 meters).

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Discussion Comments


I bet we have ethernet couplers all over our office. I know that our computers are all linked to one server, and there are cables clustered everywhere. There are bound to be dozens of couplers, because we work in several different rooms.


@giddion – Ethernet couplers can be very useful if you want to link two computers in different rooms of you home to one printer. My dad and I have computers on opposite ends of the house, but we are both linked up to one printer.

Good quality printers are expensive, so it is good that we didn't have to buy two separate ones. We have cables running up the wall and through a hole into the attic. This way, you don't see the cables all throughout the house.


Three-hundred and twenty-eight feet is way more than long enough for me! Wow, this kind of coupler must mostly be used in big offices. I can't imagine anyone needing this length of connection in their home.

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    • Cat 5 cable with RJ45 plug.
      Cat 5 cable with RJ45 plug.
    • Ethernet cables are usually used to establish physical connections to routers.
      By: vladimirs
      Ethernet cables are usually used to establish physical connections to routers.