A Beginner’s Guide to RJ45 Interface

Cables play a vital role in transmitting information across distances. To ensure successful transmission, proper connection to an RJ45 interface or RJ45 connector is crucial.

The cable’s pathway requires termination with a connector, often an RJ45 jack, which can be plugged in.

RJ45 connectors are commonly associated with Ethernet network cables and are sometimes referred to as RJ45 cables. These cables are characterized by small plastic plugs at each end, designed to fit into the RJ45 jacks present on Ethernet devices.

If you’re unsure about what RJ45 is or the various RJ45 interface types, this article will provide insights into the RJ45 interface’s significance within Ethernet connections and its relevance to related devices.

What Is RJ45 Interface?

The RJ45 interface is a widely utilized connector for Ethernet cables and networks. The term “RJ” stands for “registered jack,” which refers to a standardized interface used for connecting voice and data equipment to telecommunications services provided by local or long-distance carriers. The “45” in RJ45 signifies the specific interface standard.

In terms of physical structure, registered jacks commonly employ modular connectors and 50-pin miniature ribbon connectors.

The RJ45 connector itself is an 8-position, 8-contact (8P8C) modular plug and jack, primarily employed in Ethernet-based local area networks (LANs).

The RJ45 cable plug typically consists of a plastic housing with eight pins on the port. Among these pins, four are dedicated to transmitting and receiving data, while the remaining four may serve other functions, such as supporting various technologies or powering network devices.


RJ45 Connector vs RJ11 Connector

Apart from the RJ45 interface, there are other connector types that might lead to confusion, such as the RJ11 interface. They look similar but have distinct differences.

RJ45 vs RJ11: Connector Configurations and Size

RJ11: RJ11 connector features a 6P2C or 6P4C configuration and is primarily employed for single phone line connections. It encompasses four wires and six pins, with a smaller size measuring 6mm by 9.5mm.
RJ45: RJ45 connector adopts an 8P8C configuration, offering a more comprehensive interface. It comprises eight pins and eight wires within the cable, measuring 6mm by 11mm. Consequently, RJ45 connectors are physically larger than RJ11 connectors due to their increased wiring capacity.

RJ45 Connector vs RJ11 Connector

Application Differences: Bandwidth and Usage

RJ11: The RJ11 plug makes use of 2 or 4 of the available 6 connection points. This setup is suitable for limited-bandwidth applications like phone lines and ADSL connections.
RJ45: With its 8 contacts, RJ45 connectors provide ample bandwidth capabilities. This makes them apt for data-intensive applications such as Ethernet, supporting bandwidth up to 10Gbps. Additionally, RJ45 connectors are sometimes utilized for VoIP phones in office environments.

Technical Distinctions: Function and Usage

RJ45 vs RJ11: Although the RJ45 and RJ11 connectors might appear similar, they hold significant technical disparities. Ethernet technicians prefer RJ45 connectors for tasks such as networking computers, Wi-Fi routers, fiber modems, and NBN boxes. These connectors have become the standard in modern Ethernet connections, thanks to their support for speeds of up to 10Gbps, offering top-tier data transfer speeds and bandwidth.
RJ11: Technicians use RJ11 connectors for ADSL/VDSL and telephone connections, where their design suits the specific requirements of these applications.

Note: It is not possible to plug an RJ45 connector into an RJ11 slot. While the smaller size of an RJ11 connector might fit into an RJ45 slot, it is not recommended to do so, as this action could potentially damage the device with the RJ45 slot.

Comparing T568A and T568B Wiring Schemes for RJ45 Connectors

T568A and T568B are two commonly used wiring schemes utilized to terminate twisted-pair cables onto connector interfaces. These standards outline how the individual eight wires are arranged within RJ45 pinouts when connecting an RJ45 connector to a cable. Each of these wiring layouts follows a distinct color convention for ensuring electrical compatibility.

RJ45 Interface Color Code

Color Convention Differences in T568A vs T568B

The main difference between these two standards lies in the assignment of pins. In the 568A color code, the orange wires are connected to pins 3 and 6, while the green wires are linked to pins 1 and 2. Conversely, the T568B standard switches this arrangement, with green wires connecting to pins 3 and 6, and orange wires to pins 1 and 2.

For RJ45 Ethernet cabling networks, T568A is the favored choice due to its compatibility with the wiring schemes of the Universal Service Ordering Code. It is commonly used in Ethernet cables across Europe, the Pacific region, and U.S. government offices.

On the other hand, the T568B color code aligns with the Ethernet cabling networks designed according to AT&T 258A color code standards and ANSI/TIA-568C. This standard finds popularity in U.S. business Ethernet connections.

Considering these standards, two distinct connectivity forms emerge. If both ends of patch cords adhere to the same standard, it results in a straight-through connection. Conversely, a crossover connection is established if the standards differ between the two ends. Crossover Ethernet cables, featuring a T-568A connector on one end and a T-568B connector on the other, are employed in networking applications where direct computer-to-computer connections are necessary, circumventing the need for a router, hub, or switch.

RJ45 Cable Types

Ethernet cables terminated with RJ45 connectors on both ends are commonly referred to as RJ45 Ethernet cables. In modern network connections, the most prevalent types of RJ45 cables include Cat5, Cat6, and Cat7 cables.

Cat5 vs Cat5e

Initially, Category 5 was designed for transmitting at 100 MHz frequencies, offering a rated line speed of 100 Mbit/s. Cat 5 cables utilize two twisted pairs (four contacts) and have a maximum range of 100 meters. Subsequently, a more stringent specification, Cat5e, was introduced. This newer standard mandated that cables include all four twisted pairs.

In cases of short distances and optimal signal conditions, provided they possess four pairs, both Cat5 and Cat5e patch cables can achieve Gigabit Ethernet speeds. Gigabit Ethernet employs a specialized encoding scheme tailored for effective operation within these lower signal tolerances.

Cat6 vs Cat6a

Cat6 cable is backward compatible with Cat5e and comes with stricter standards and enhanced shielding. It was established as the benchmark for Gigabit Ethernet, offering inherent speeds of up to 1000 Mbit/s across a 250 MHz frequency. Additionally, the maximum cable distance for Cat6 was reduced from 100 meters to 55 meters, allowing support for 10 Gigabit Ethernet.

Cat6a further elevates the frequency to 500 MHz while maintaining noise reduction through grounded foil shielding. These advancements eliminate the cable distance limitation when operating in 10 Gigabit Ethernet mode.

Category 7

Cat7 was developed to handle frequencies of up to 600 MHz, making it tailored for the rated speeds of 10 Gigabit Ethernet. Building upon the shielding features of Cat6e, this upgraded specification adds individual shielding for all four twisted pairs. Despite its maximum distance being 100 meters, Cat7 remains backward compatible with Cat5 and Cat6.

Cat7a takes the frequencies a step further to 1000 MHz, presenting an enhanced specification that can potentially support future 40/100 Gigabit Ethernet speeds. The boost to 1000 MHz also facilitates the transmission of lower-frequency Cable TV streams.

RJ45 Cable Applications

RJ45 connectors play a pivotal role in enabling Ethernet connectivity for voice and data transmission. They emerged as compact and cost-effective alternatives to the traditional hardwired telephone installation techniques. The convenient plug-and-play design simplifies installation procedures. Unlike RJ11, RJ45 finds utility in a wider array of applications, encompassing Ethernet networking, telecommunications, factory automation, and beyond. It serves as a common choice for various networking devices, including Ethernet cables, modems, computers, laptops, printers, and more.

RJ45 application


RJ45 cables, connectors, and interfaces form the essential foundation of seamless Ethernet connections. This hardware facilitates the transmission of data, power, and connectivity, playing a pivotal role. In essence, the absence of these components would hinder enterprises from harnessing the advantages of Ethernet technology.

As a prominent distributor, Bonelinks offers a comprehensive range of hardware required for Ethernet connections. Feel free to reach out to us to acquire all the necessary insights and tools for establishing efficient Ethernet connections.

Echo Huang

Echo Huang is an expert wordsmith and marketing professional at Bonelinks with more than 8 years of experience in high technology businesses – fiber optics, IoT, and telecommunication. She is very glad to share industry knowledge and communicate with others.

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