What Is an RJ45 Port on a PCB?

Ever since the introduction of Ethernet, the RJ-45 port (or RJ-45 jack) has become the standard for connecting wired LANs in commercial settings. When used on PCBs and in panel-mount versions, these connectors come in two common formats: magjack and non-magjack, and there are some specialized connector options that provide superior ingress protection ratings. While a common usage is in home networking equipment, today, it's common to see an Ethernet connector alongside a fiber connector in embedded devices, rack-mount computers, and single-board computers. As of 2026, these connectors have evolved to support Multi-Gigabit Ethernet (2.5G, 5G, and 10G) while maintaining the same familiar form factor.

When integrating an Ethernet connector into your design, they typically come in two common formats:

• MagJack Ethernet Connector: These "integrated magnetics" connectors contain the necessary transformers and common-mode chokes inside the housing. This saves significant board space and simplifies the RJ45 termination circuit by handling EMI and isolation internally.
• Non-MagJack (Standard) Jacks: These are simple mechanical housings that require external magnetics (discrete transformers) placed on the PCB. These are often preferred in ultra-slim designs or specialized industrial applications where custom magnetic isolation is required.

While a common usage is in home networking equipment, today, it's standard to see several PCB Ethernet jack types alongside fiber-optic SFP+ modules in embedded devices, rack-mount servers, and high-performance single-board computers (SBCs). In ruggedized environments, specialized versions with high ingress protection (IP67/IP68) ratings ensure reliable connectivity even in harsh conditions.

Whether you are designing for a simple 10/100 Mbps link or a high-speed 10GbE interface, selecting the right RJ45 connector and understanding the Ethernet magnetics required for your Ethernet controller is the first step toward a successful networking design.

Types of RJ-45 Ports

Not all RJ-45 ports are created equal. Depending on your project's needs, you might encounter various types, each with features that suit a particular environment or application. As of 2026, the industry has pushed toward higher integration and faster data rates even in standard form factors. Below, we'll take a look at some of the most common types.

1. Single RJ-45 Port

The RJ-45 female connector (a.k.a., RJ-45 jack) is designed to receive an RJ-45 male plug on an Ethernet cable. These connectors are used when a device only needs a single Ethernet port or a small number of Ethernet ports. 

• Unshielded Jacks: These feature a plastic casing and are used in cost-sensitive applications where electromagnetic interference (EMI) is not a primary concern. They cannot provide a ground connection to a shielded cable.

• Shielded Jacks: These feature a metal "can" or shroud that connects to the PCB's chassis ground. They are essential for protecting high-speed data signals from interference and are required when using shielded twisted-pair (STP) cabling.

2. RJ-45 Multi-Port Jacks

Many networking devices will have groups of ports bundled together in a single component. These multi-port jacks are most often magjacks that mount to a PCB as through-hole components and contain indicator LEDs for each port. Multi-port jacks can generally support Gbps data rates (1000Base-T). These are referred to as "Ganged" (side-by-side) or "Stacked" (one above the other) jacks.

• Integrated Magnetics: Most modern multi-port jacks are magjack Ethernet connectors. By containing the isolation transformers and common-mode chokes inside a single housing, they significantly reduce the PCB footprint.
• Speed and Feedback: These jacks generally support 1000Base-T (Gbps) data rates, with 2026 models increasingly supporting 2.5G and 5G speeds. They almost always include integrated indicator LEDs (usually green and yellow) to provide immediate link and activity status.
• Mounting: These are most often through-hole components to provide the mechanical strength needed to withstand the friction and leverage of multiple cable insertions.

RJ-45 Port Termination

Those who are familiar with Ethernet design or with Ethernet standards will know that Ethernet Rx and Tx lanes must be terminated somewhere on the PCB before a connection is made to the RJ-45 port. The termination is performed with a set of magnetic chokes and coupled inductors, as well as a resistor network on the output side of the termination circuit. This is called""Bob Smith terminatio"" and it provides galvanic isolation, common-mode noise suppression, and impedance matching to the RJ-45 port and cable.

The magnetics termination circuit could be built from discrete components, particularly through the use of an ethernet transformer and ethernet common-mode choke. However, many RJ-45 ports today include the magnetics termination circuit built into the connector, known as a magjack connector. To locate these connectors, make sure to search for RJ-45 magjack on Octopart.

Note that gigabit Ethernet interfaces will use 4 pairs of signals and will fill up all of the pins on the RJ-45 port. This will result in the above diagram having 4 magnetics termination circuits instead of 2.

Because the termination circuit enforces galvanic isolation, the grounding scheme is typically designed with a chassis ground and a system ground. Getting this incorrect can create an EMC failure, either due to ESD testing failure or radiated emissions. To learn more about magnetics termination and the required grounding strategy in each case, read this article on Altium Resources.

RJ-45 Ports on the PCB

When wiring an RJ-45 port on the end of an Ethernet cable, there are two standard schemes to follow: T568A and T568B. Each is used for different purposes, but the main difference lies in how the wires are paired. RJ-45 ports on the PCB will have a pinout that is totally independent of the use of a T568A or T568B scheme. For example, if you look in an RJ-45 magjack datasheet, you will see a diagram that shows the cable pin numbering linkage to the PCB pin numbering across the magnetics termination circuit.

In addition, on shielded RJ-45 ports, there could be another 4 pins to power the two LEDs on the sides of the connector body. These LEDs should receive power from the system GND side of the termination circuit. An example for the JX0026D21NL from Pulse is shown below.

Integrated LED and Shielding Pins

Modern connectors often include extra pins beyond the standard 8 signal pins:

• Shielding Pins: On shielded jacks, these connect the metal shroud to the chassis ground.
• LED Pins: Many jacks include four additional pins to power two integrated LEDs (usually for "Link" and "Activity" status).

These LEDs should receive their power and control signals from the system ground side of the termination circuit, not the isolated chassis ground. A classic example of this high-integration design is the JX0026D21NL from Pulse. This part is a staple in 2026 industrial designs because it combines the RJ-45 jack, magnetics, and LEDs into a single, compact through-hole package.

Where You'll Find RJ-45 Ports

From homes to industrial environments, RJ-45 ports are essential in maintaining stable communication between devices. While wireless tech is everywhere, the "reliability of wire" remains the gold standard in 2026 for mission-critical data. Let's explore some of their most common uses.

1. Embedded Computing

Many embedded devices forego the use of wireless networking in favor of wired networking over copper or fiber. High-compute embedded devices that are part of a larger network may feature RJ-45 for copper connections and an SFP (Small Form-factor Pluggable) transceiver receptacle for fiber connections. This dual-path approach allows the same device to interface with traditional LANs or high-speed fiber backbones.

2. Data Centers

Data centers rely heavily on wired and optical connections to maintain high-speed data transmission across servers and storage systems. RJ-45 ports and Ethernet cabling are used for shorter distance, lower bandwidth links, while higher-speed, longer-distance links will use optical fiber or active copper interconnects (e.g., over twinax cabling) for interconnects between server clusters requiring much greater processing and computing.

• RJ-45 (10GBASE-T): Typically used for shorter distances (under 100 meters) and connections between top-of-rack (ToR) switches and servers.
• Fiber/DAC: For links exceeding 100 meters or requiring bandwidths of 25G, 100G, and beyond, engineers pivot to optical fiber or Direct Attach Copper (DAC) cables. This avoids the "copper wall" where heat and signal attenuation make RJ-45 impractical for ultra-high-density clusters.

3. Industrial Applications

In manufacturing, energy, automation, and other industrial settings, shielded RJ-45 ports are used for data transmission between production and computing assets. These connectors may be rugged versions of panel-mount connectors with high IP ratings to ensure they can withstand ingress and mechanical damage.

• Ruggedization: These ports often feature metal shells (Aluminium or Stainless Steel) and are sealed to IP67 or IP68 ratings to protect against dust, moisture, and vibration.
• Field Termination: Industrial settings frequently use "field-installable" RJ-45 plugs that don't require specialized crimping tools, allowing for rapid repairs on the factory floor.

4. Home Networking

RJ-45 ports are just as important in home networking. Computers, routers, and modems all typically use unshielded RJ-45 ports as a low-cost solution for connecting devices. Because these systems typically are built from plastic and do not have an earth connection or chassis GND, they do not need to use a shielded RJ-45 port.

Compare & Find RJ-45 Ports for Your PCB

Whether you are looking for a high-performance magjack Ethernet connector for an industrial controller or a low-profile RJ45 port on PCB for a compact embedded device, having the right data at your fingertips is essential. In the fast-moving semiconductor market of 2026, real-time insights into lead times and technical specifications are the keys to a successful production run.

Octopart makes your search a snap with a platform that lets you explore a vast inventory of RJ-45 ports, cables and wires, and advanced networking components from authorized distributors. Our platform allows you to:

• Filter by Specification: Narrow down your search by data rate (10/100, GbE, 10GbE), mounting type (SMT vs. Through-hole), and shielding options.
• Verify Compliance: Instantly check for RoHS and REACH compliance, as well as IP ratings for ruggedized industrial connectors.
• Analyze Market Trends: View historical pricing and stock levels to ensure your RJ45 termination circuit design is built around components with long-term availability.

Easily compare options, check real-time availability, and find the perfect electronic components for your project today!

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Frequently Asked Questions About RJ-45 Ports

Below, we've addressed some additional questions concerning RJ-45 ports. Explore additional FAQs, then compare RJ-45 ports at Octopart.com to determine which will best suit your needs. 

Can an RJ-45 port be used for PoE (Power over Ethernet)?

The standard RJ-45 ports used on Ethernet cables can be used for PoE, but a PoE-compatible RJ45 port must be used on the PCB. Power over Ethernet enables data and electrical power to transmit over a single Ethernet cable, which eliminates the need for separate power sources for network devices like IP cameras, VoIP phones, and wireless access points. Many modern RJ-45 ports, especially those used in Cat6 or higher cabling, are PoE-compatible, but only if the receptacle on the PCB is designed to work with PoE.

What is the difference between a shielded and unshielded RJ-45 port?

A shielded RJ-45 port is assembled with a metal housing that protects against electromagnetic interference (EMI). The use of metal housing connectors is standard in systems that have a metal chassis, as the metal shielding can be connected to the chassis GND. This allows a shielded Ethernet cable to be used, although one should note that the shielding needs to be connected to the chassis and/or system GND at each end of the link to provide any shielding against EMI without also causing a new conducted or radiated emissions problem.

Can I use an RJ-45 port for non-Ethernet applications?

Although RJ-45 ports are primarily used for Ethernet networking, they can also be used in non-Ethernet applications such as serial communication, telecommunications, or custom cable configurations. However, depending on the application, these use cases may require different wiring arrangements or adapters. For example, rack-mount networking switches and routers can include a serial port (RS232) over an unterminated (non-magjack) RJ45 port. Be careful with this usage because the output on these cables is typically unfiltered, and any common mode noise on the cable could result in an EMC testing failure.