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Introduction to RJ45 Connector

Introduction to RJ45 Connector

Posted by NavePoint on May 12th 2021

What is “RJ45”?

RJ45 is a type of connector commonly used for Ethernet networking. The "RJ" in RJ45 stands for "registered jack." Registered interfaces were first defined in the Universal Service Ordering Code (USOC) system of the Bell System to comply with the mandate by the Federal Communications Commission (FCC) in the 1970s. The Registered Jacks were subsequently codified in title 47 of the Code of Federal Regulations Part 68. The "45" in RJ45 simply refers to the 45th code of the interface standard.

Although we often see the RJ45 as a connector, technically, RJ45 is a wiring standard that does not have a physical form.

8P8C vs. RJ45

8P8C stands for “8 position 8 contact” modular connectors. RJ45 describes a wiring standard that uses an 8P8C connector. In other words, the "RJ45 connector" should be called the "8P8C connector with RJ45 wiring." However, to keep the blog post concise, we will continue to use the phrase "RJ45 connector" with the understanding that it is technically incorrect

TIA-568A vs. TIA-568B

TIA-568 is a set of telecommunications standards from the Telecommunications Industry Association (TIA). Standards T568A and T568B are the pin-pair assignments for eight-conductor 100-ohm balanced twisted-pair cabling to the 8P8C modular connectors. Each RJ45 connector has eight pins, which means an RJ45 cable contains eight separate wires. If you look closely at the end of an Ethernet cable, you can see that four of them are solid colors, while the other four are striped.

Note, between the pinout for T-568A and the pinout for T-568B, the colors green and orange are flipped. If you are connecting into existing ethernet networks, it is important to figure out whether the male or female that your connector is plugging into is T-568A or T-568B. The rule of thumb is to follow the existing pinout schematic because they should not be used interchangeably. However, in the instance where the previous reference does not exist, use T-568A for installing in a residential or a government contract setting.

Wire Diameter

Not all RJ45 connectors are the same and they are not a one size fit all CAT cables type of solution. When buying RJ45 connectors, always check the connector's fitment specifications, or the Cable Jack Diameter, and the Conductor Insulation Diameter allowed. Cable Jack Diameter refers to the outer diameter of your ethernet cable, and the Conductor Insulation Diameter refers to the outer diameter of each individual wire inside your ethernet cable. Make sure both the cable and the wires fit into the connector of choice.

Shielded vs Unshielded

To install a shielded system, you need to pair shielded cables with shielded connectors. In our previous blog FTP vs UTP: Cutting Through the Noise, we discussed the different types of shielding in cables. Fortunately, there is only one type of shielding in connectors, so make sure you buy shielded connectors for your shielded system. In future posts, we will discuss the importance of a shielded system. Make sure you sign up for our newsletter to stay up to date on our latest blogs!

To Boot or Not To Boot

The boot cover is a rubber component that protects the connector from bulk cable snags while providing strain relief. It can be slid over or molded over the RJ45 connector. Strain relief that is molded over the connector provides the best snag protection. The two main advantages of boot covers are dust protection and to decrease the risk of an accidental disconnect.

There are three main types of boots in the market:

  • Dome type boot

  • Hook type boot

  • Ears type boot

The dome-type boot provides the most resistance when you try to disconnect the connector, making it the best choice for connections that should stay as-is for a long period.

The hook-type boot offers the least resistance when you try to disconnect the connector, making it the best choice for connections that requires frequent reconnections.

The ears-type boot falls in between the two other types in terms of the difficulty to disconnect while offering a good amount of protection from accidental disconnects.

Note, boots for shielded and unshielded RJ45 connectors are not interchangeable, so make sure you buy the right boot for your shielding need.


In summary, RJ45 is a wiring standard and 8P8C is the type of connector used for our RJ45 ethernet connections. T-568A and T-568B pinouts should not be used interchangeably. Make sure you buy a connector that will fit the diameters of your cable, and if you have shielding needs, buy a shielded connector. Boots are not required, but they are recommended. Different types of boots will generate different levels of resistance when disconnecting the cable. So, decide what type of boot best fits your needs. Molded strain reliefs are better at protecting from snags than assembled strain reliefs. Check out NavePoint’s selection of patch cables!

Contact NavePoint’s sales or customer service team at 888-505-1363 to learn more about how we may be able to help with your specific need!

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