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The most comprehensive RJ45 plugs introduction



You guys may have seen the RJ45 modular plug. Why do people call it rj45? What are its types? This article will explain in detail the knowledge about RJ45 plug.

What is RJ45 modular plug?


RJ45, also known as Registered Jack 45, is a connection plug used in electrical signal transmission systems, commonly used in wiring systems. The RJ45 modular plug is composed of a connector and a socket. The connectors consisting of these two components are connected between the wires to achieve electrical continuity of the ethernet cables.


Figure: RJ45 plug


Registered jack consists of the modular connector and the 8-pin miniature ribbon connector. RJ45 plug is an 8-position, 8-contact (8P8C) modular plug, applied for Ethernet-based local area networks (LAN). 


In 2021, RJ45 plugs can be seen in almost all work and life scenarios. From the RJ45 interface of the nic card in each office or the RJ45 interface of the home router, we rely on the use of this type of interface to transmit data.


The structure of RJ45 modular Plugs


According to the hole position and contact point, the crystal head type is 4P2C, 4P4C, 8P8C in the data and voice system. P (Position) stands for the vacant position of the crystal head, and C (Contact) is the electrical contact position with a gold-plated phosphor bronze surface. The type adopted by RJ45 is 8P8C, while the RJ21 plug has two types, 4P2C and 4P4C.






Telephone line, used for voice applications

Data communication










Less than 24Mbps

Less than 40Gbps(Cat8)


Compact, square-shaped

Longer, more rectangular


T568A and T568B,what is the difference?



                                                                                                                               Figure: T658A VS T658B


T568A and T568B are the two color code schemes used for wiring eight-position RJ45 modular plugs. As you can see in the figure below, the only difference between the pin assignments of the two is that the positions of the orange and green wires are interchanged. The ANSI-approved Telecommunications Industry Association (ANSI/TIA) defines the color code scheme.


There is almost no difference in performance between the two, except that the US government contract requires the use of T658A. In most cases which one to choose depends entirely on your preferences. But remember that the same color scheme must be used at both ends of the cable. It is also necessary to maintain a scheme of RJ45 cables to implement the entire project in the actual project. In most cases, T658B is the more common choice.

The application of RJ45 connectors


RJ45 is mainly used for data transmission on Ethernet networking. Standard equipment includes PC network cards, data switches, WiFi access points, and routers. Since the transmission distance of the RJ45 network cable is limited to less than 100 meters, its application is often in indoor scenarios. The most significant advantage of RJ45 network cable over other cables is that it can be used for POE power supply, which is not possible for fiber optic cables. This critical advantage is reflected in the wiring of the monitoring system.

RJ45 modular plug types you should know.


RJ45 connectors types including cat5,cat5e,cat6,cat6a.cat7,cat8. Following paragraph will introduce them.


cat5 vs cat5e


Cat5e is a performance-enhanced version of CAT5. CAT5 can transmit 100MBbps of data at a distance of 100M, while CAT5E is ten times that of it, reaching 1000Mbps. In addition, CAT5e cables have stricter requirements on the tightness of wire stranding than CAT5; tighter stranded wires are equal to less crosstalk interference. In 2021, it can say that CAT5 network cables are relatively rare, and everyone will choose higher specifications such as Cat5e or Cat6.


cat6 vs cat6a

Cat 6a cable

     Figure: Cat6a rj45 connector


The transmission rate of cat6 and cat6a has reached 10Gbps. The main difference in performance between the two is that the maximum transmission distance of Cat6 under 10Gpbs is 55m, while Cat6a is 100m. From the appearance point of view, Cat6a is much thicker than Cat6. The wire diameter of Cat6 is 22~24AWG, while Cat6a is 16~20AWG. Cat6a doubles the bandwidth frequency of data transmission from 250 MHz (Cat6) to 500 MHz. Higher bandwidth allows for more reliable data transmission, including over greater distances. In addition, Cat6a is a shielded cable, dramatically improving its anti-electromagnetic interference performance and is suitable for industrial environments.

RJ45 cat 7


The working frequency of Cat7 has been further improved based on Cat6a, reaching 600Mhz. The shielding performance has also been further improved. Each of the four pairs of twisted pairs of Cat7 provides separate shielding.

Cat 8 RJ45 connector

 Cat 8 cable

     Figure: Cat8 rj45 connector

The operating frequency of Cat8 has reached an astonishing 2000Mhz. Thanks to the extremely high operating frequency, cat 8 ethernet cable speed has reached 25G/40Gbps, but its transmission distance is only 30m. The Cat 8 cable price is not expensive, about 15% higher than the price of cat6a. Due to the 25G/40Gbps copper cable network applications are relatively rare, Cat8 is not very common in our life. Cat8 is generally used in the TOR structure of enterprise-level data centers.



After reading this article, you have a deeper understanding of RJ45 modular plugs. As a copper core cable, the RJ45 ethernet cable also has shortcomings: high cost, heavier weight, short transmission distance, and other flaws. If you have any questions about RJ45 or network cables, please get in touch with QSFPTEK for more knowledge.



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