Plug In an Power Up: The Beginner's Guide to RJ45 Connectors
By: CableOrganizer®
When you’re looking to achieve a strong, stable, network performance, the small yet mighty RJ45 Connector is a pivotal part of wired networking infrastructure within homes, offices, and data centers.
An Introduction to the RJ45 Connector and Its Predecessors
Beginning in the mid-1970s, the Registered Jack or “RJ” standards were introduced by the Bell System as the wiring standards and telecommunications interface definitions. The Federal Communications Commission (FCC) codified it under the U.S. Code of Federal Regulations, 47 CFR Part 68. Before the 8-position, 8-conductor (also often referred to as 8P8C) RJ45 was the standard for Ethernet though, there were other Registered Jacks, including the RJ11 and the RJ12. The 6-position, 2-conductor RJ11 was primarily created for landline telephones. It is much smaller than the RJ45, and carries voice signals, as well as very low-speed modem data, such as for a fax machine. The RJ12, primarily for multi-line phone systems, and secondarily low-speed serial data, also features a 6-position connector, but has 6 conductors to support more lines and connections. RJ14 is another type with 6-positions and 4-conductors, which makes it useful for two-line analog telephone systems in business applications, or home phones with two lines. Although it is not suitable for Ethernet, it has been used for data applications. The RJ18, rarely seen today, was created as a 6-position, 6-conductor jack for one telephone line to create “make-busy” functionality in PBX systems. An RJ21 is another type of Registered Jack designed to connect up to 25 telephone lines through an Amphenol 50-pin connector. It may still be found in legacy telephone systems and datacomm applications. One of the uncommon Registered Jacks is the RJ22, the smallest style RJ Connector to connect a telephone handset to the phone base. It only carries audio, and never data or network signals. Three telephone lines could be supported simultaneously with the RJ25, a 6-position, 6-conductor Registered Jack. The 8-position, 8-conductor RJ31 may physically resemble the RJ45, but the pinouts and intended wiring are different because it was made to connect alarm or security systems to phone lines, enabling an emergency call to be dialed, even if another device is using the phone line.
In the pre-RJ45 era of the earliest 1970s-1980s computing networks, Coaxial Cables with BNC or N Connectors were the standard. BNC was common for 10BASE2 and 10BASE5 Ethernet, while N-type Connectors were used in older broadband or high-frequency RF applications. But, by the late 1980s and early 1990s, twisted-pair Cat3 cabling became the medium for 10BASE-T Ethernet, with Cat5 cabling a replacement for Coaxial Cables in 100BASE-TX networks. While RJ11 and RJ12 were the connectors of the dial-up internet days for telephone modems, the RJ45 became the norm for 10BASE-T and 100BASE-TX Ethernet.
The RJ45 is now the standard component in Local Area Networks (LANs), connecting and terminating twisted-pair copper network cables, such as the Cat5e, Cat6, or Cat6a, in high-speed data transmission. RJ45 initially referred to the exact Registered Jack wiring specification for telecommunications, and colloquially, RJ45 is the name often used for the 8P8C modular Ethernet Connector. Anywhere a wired connection is required, whether it is a smart home, server rack, or office building, an RJ45 will be found.
How RJ45 Connectors Interface with Ethernet (CAT) Cables
The RJ45 became the standard to terminate Category or “Cat” Cables like the Cat 5e, Cat6, and Cat6a. These twisted-pair Ethernet Cables feature eight separate wires that are twisted into four color-coded pairs to collectively carry data signals. An RJ45 Connector organizes and secures the wiring to establish a connection between network devices.
The eight wires in an Ethernet Cable are then arranged into specific wiring standards, known as T568A and T568B terminations. Both standards electrically function the same way but differ in their wire pair color assignments. This CableOrganizer® article here goes in depth to explain the differences between these two standards. The T568B wiring scheme is used for most new installations within the United States, while T568A is frequently mandated as the preferred standard for U.S. government federal contracts.
The RJ45 Connector Types
Choosing the right RJ45 Connector is also crucial to your application. The differing connectors include:
Traditional Crimp-Style: This is the most recognizable RJ45 Connector and installing it entails using a Crimping Tool to push the pins into the wires and lock the connector into place. This type creates the most secure and reliable connections, making it beneficial for permanent and/or high-performance setups.
Toolless: Some RJ45 Connectors are toolless and designed to install quickly without a Crimping Tool. This type is convenient for field applications, is reusable, and features a built-in mechanism to secure wires.
Unshielded: These are standard RJ45 Connectors for unshielded Cat cables. Unshielded Cables are used for most general, low-interference applications, such as homes or offices. This type of cable is more flexible, and easier to install than Shielded Cables.
Shielded: Shielded Cables protect against electromagnetic interference (EMI), which is high-frequency noise. This type of cable features a foil or braid layer that reduces electrical disturbances in places like data centers and industrial environments. Using a Shielded RJ45 with a Shielded Cable maintains the effectiveness of the cable’s protective properties, defending it from interference.
Industrial/Heavy Duty: Some outdoor and harsh environments call for rugged materials that protect outdoor networking applications. CableOrganizer® offers Industrial Coupler Feed Through Kits, for example, that keep RJ45s watertight, safeguarding them from moisture and dust. Industrial RJ45s are commonly used for Closed-Circuit Television (CCTV), transportation applications, factory automation, and more, where both durability and environmental protection are critical. It may include Ingress Protection (IP), such as an IP68 waterproof-rated sealing, as well as rubber gaskets, metal housings, and vibration resistance. IP68 signifies this type of connector is resistant to water and dust.
Equipping Cables for the RJ45 Installation
Cables should be properly readied to receive the RJ45 Connector. This is done to establish a reliable and strong electrical connection between network devices. The steps to prep cables for a connector include:
Outfitting Cables for an RJ45 Fit: Remove the Ethernet Cable jacket with a wire stripper to expose its eight inner wires. Each pair needs to be untwisted, and while this can be done by hand, some experts suggest simultaneously separating and untwisting the pairs with a small screwdriver, carefully pulled from the bottom to the top of the cable’s exposed section. From there, the uncurled wires inside the cable jacket can be arranged in either the T568B or T568A order. See our article here for each standard’s wiring order and watch our video here.
Trimming and Aligning Cables: Trim cables with cutters to a uniform length, then insert them into the RJ45 Connector slots, which include eight parallel grooves that line up with the cable’s eight conductors.
Terminating Cables: A crimper is a tool that pushes metal contacts (called pins) and presses (crimps) the RJ45 Connector onto the wires. When these contacts pierce the wire’s insulation, they can create a steady electrical connection. After crimping, the RJ45 is snapped into an Ethernet port, such as one in a Patch Panel, locking the connector into place for a secure fit. If any excess wires remain, they can be trimmed back. Once the first end of a cable is terminated with a connector, the process can be repeated for the cable’s opposite end. Read our article here for step-by-step instructions and images that show this full process.
Testing the Connection
It is crucial to ensure newly terminated cables fully function. Network Cable Testers are tools that can be utilized to remotely test cables terminated with RJ45 Connectors. To generally use a tester, first turn it on, then plug the RJ45-terminated cable ends into the tester’s port(s). Some testers have a manual or automatic test mode and then will illuminate with LEDs to indicate specific faults, successful continuity, general connectivity, and various other test results. Remote Cable Testers often have a main unit and a detachable piece that is used to test remote equipment. Signals will be sent through each wire pair, with LEDs lighting to indicate that signals are functioning properly. Testers also identify shorts, opens, miswires, reverses, and split pairs. Some more advanced Time Domain Reflectometry (TDR) or certification-style testers send a voltage pulse with specific signal patterns, depending on the tester. When cable tracing is performed, a test that identifies a cable, a tone signal is typically emitted. There are additionally the PATCH APP & GO Testers. These plug in physically, with one person operating the units, and are used in conjunction with a phone app, where pass or fail results are displayed. Read our article to learn further how to test an RJ45 Connection here, and how to remotely test RJ45 terminated cables in our article here.
When to Troubleshoot your RJ45 Connector
If your Ethernet Cable doesn’t seem to be working, a faulty termination could be the cause. You will know if your signal is intermittent or you have no network connection at all. Slower than usual transmission speeds could be another sign. And there could be physical evidence of a bad termination like loose plugs, wires that pull out, or cables that are visibly misaligned inside the RJ45 Connector. Performing a network test using a test instrument like a LAN Cable Tester, can determine the pinout is properly arranged in T568B or T568A order, also checking for continuity, open circuits, split pairs, or miswires. LAN Network Certification using Cable Certifiers can check the performance of the installed cable link/channel in specific categories, and a basic LAN cable tester is unable to do so. These certifiers measure against standards like ANSI (American National Standards Institute) and the Telecommunications Industry Association (TIA), including ANSI/TIA-568, which was developed to standardize commercial building telecommunications cabling. A fix may require re-stripping and re-crimping the RJ45 Connector, paying special attention to confirm the wire order is accurate and insertion into the Category (Cat) Cable is correctly done.
When It is Appropriate to Replace a RJ45 Connector
There could be numerous factors, beyond a faulty termination, why an 8P8C RJ45 needs replacing. General wear and tear from frequent plugging and unplugging in high-use areas could impact it, causing damage to the connector’s pins. A loose fit or broken latch is another basis for replacement. You may need to swap an RJ45 for a new one, because of frayed cable ends and corrosion. An upgrade could also be in order if you’re using connectors not rated for the cable category and installation speed. And making a switch from unshielded to shielded cables will require a similar switch to shielded RJ45 plugs, to make sure the EMI protection and grounding are evenly matched. This is because shielded cables have a thicker construction with a foil or braided inner lining that protects against EMI. CableOrganizer® also carries Unshielded and Shielded Patch Cords with the appropriate RJ45 Connectors included.
Explore the full RJ45 Connectors and Accessories Category at CableOrganizer® here.
