RJ45 Connector for Ethernet Cable Termination

It is known that fiber optic cable is often used fiber optic connector, like LC, SC, to achieve termination. How about Ethernet cables? That is RJ45 connector or RJ45 plug, which is a common component terminated with Ethernet cables to achieve the connection between computer and Ethernet-based local area network(LAN). The letter “RJ” means registered jack, which is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by local exchange carrier or long distance carrier. This post aims to introduce this type of Ethernet connector and offers some simple guidance for terminating Ethernet cable with RJ45 connectors.

What Is RJ45 Connector?

RJ45 is the commonly used twisted-pair connector for Ethernet cable and networks. It is usually made of a transparent plastic piece with eight pins on the port as shown below. Four of the pins are used for sending and receiving data, and the other four are used for other technologies or power networking devices. So this type of connector is also called as 8P8C (Eight Position, Eight Contact) modular connector. It can be inserted along a fixed direction and automatically prevent shedding used for most applications, such as Ethernet networking, telecommunications, factory automation and so on. The RJ45 is originally invented to replace the bulkier connector for connecting modems to telephones in the telecommunication industry, but nowadays, it is most commonly applied for networking devices including Ethernet cables, modems, computers, laptops, etc.

RJ45 connector

Differences Between RJ45 and RJ11

Besides RJ45, there are many other types of RJ-style connectors on the market, RJ11 is one of them. RJ11 connector has similar appearance as RJ45, so people often mix them together. Actually, these two connector types have their own specific purposes. The biggest difference between them is in where they are actually used. RJ45 connector is used in networking, where you connect computers or other network elements to each other, while RJ11 is the cable connector that is being used in telephone sets.

Aside from the application, there are also differences that an individual can easily see and identify. The first of which is in the number of cables that are accommodated in each connector. If you look closely at both connectors, you would see that there are only four wires inside the RJ11, while eight wires inside an RJ45. As a consequences of having to accommodate more wires, RJ45 is a little bit bigger than RJ11. You should keep in mind although it is possible to physically fit an RJ11 connector into an RJ45 receptacle, this will never function for an actual Ethernet connection, or you will damage the device that has the RJ45 slot. We can see their differences in the image below.

RJ45 vs. RJ11

RJ45 Wiring Diagram For Ethernet Cable

According to ANSI, TIA & EIA, there are two variations of RJ45 wiring diagram: T568A and T568B. Both T568A and T568B provide wiring schemes for terminating twisted-pair copper network cable to RJ45 connectors. The pairs in these cables consist of four colors (blue, orange, green, and brown), with each pair includes a solid-colored wire twisted with a wire of the same color, with white stripes.

When looking closely at the two wring diagrams below, the only visual difference between T568A and T568B is that the pin positions for the green and orange pairs are flipped as shown below. Besides the color placement variances, there are a couple of compatibility factors that can affect the choice of an RJ45 wiring scheme. T568B is a more up-to-date scheme and also the most widely chosen wiring schematic, because it matches AT & T’s old 258A color codes, meanwhile, T568B accommodates for current and future needs.

T568A vs. T568B

When building a new network, one may technically pick any one of the wiring schemes. No one scheme is better than the other, or is better suited for specific things. Both schemes are perfectly fitted for any installation type. But when an existing network is being expanded, it is crucial to use the scheme in place.

How to Terminate Ethernet Cable With RJ45 Connector?

Step1: Using a crimping tool, trim the end of the cable you’re terminating, to ensure that the ends of the conducting wires are even. Then strip off approximately 1 inch of the cable’s jacket.

Step2: Separating the 4 twisted wire pairs from each other, then unwind each pair, so that you end up with 8 individual wires. Flatten the wires out as much as possible, since they’ll need to be very straight for proper insertion into the connector.

Step3: Holding the RJ45 connector, so that its pins are facing away from you. Moving from the left to right, rearrange the wires according to the wiring scheme.

Step4: Holding the connector, and carefully insert the wires into the connector, pushing through until the wire ends emerge from the pins. Check to make sure that the wire ends are in the correct order. If not, repeat the steps2 to step3 again.

Step5: Inserting the prepared connector/cable assembly into the RJ45 slot in your crimping tool. Firmly squeeze the crimper’s handles together until you can’t go any further.

Step6: Carefully cut wire ends to make them as flush with the connector’s surface as possible.

Step7: To make sure you’ve successfully terminated each end of the cable, use a cable tester to test each pin.


The RJ45 plug, with easy plug-and-play style, reducing the difficulty of installation, is one of the most popular connector type nowadays. A lot of people have begun to place RJ45 connectors on wall outlet inside their houses in order to reduce the number of visible wiring. Hope this post can help you better understand RJ45 connector and how to use them to terminate Ethernet cables.


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