Selecting the Correct Connector

Selecting the Correct Connector

Written by Don Schultz, Technical Sales Representative and Fluke Networks Certified Technician

All Ethernet cable must be terminated at both ends. One way is to use a RJ45 connector. Selecting the correct connector for your Ethernet data cable is entirely dependent upon the type and construction of the cable to be run.

First Things First. Do I Need A Shielded Connector?

If the cable is shielded, you will want to use shielded RJ45 connectors. Conversely, if the cable is unshielded, you will want to use unshielded RJ45 connectors. Using a shielded connector on an unshielded cable will yield no benefit, although it won't cause issues. The same cannot be said for using an unshielded connector on a shielded cable. Shielded cables need shielded connectors for the ground and shield to function properly.

Shielded vs Unshielded RJ45 Connectors

Once you have decided on whether the RJ45 connector (also referred to as a plug) should be shielded or not, the next thing is…

Research for the Right Cable & Plug

Any reputable manufacturer will have detailed specifications and publish them. Avoid any manufacturer that does not publish all of the required details. They are likely not a manufacturer, but simply a reseller that will offer little to no support on the products.

For the Ethernet cable you will need to know:

  • OD (outside diameter) of the Ethernet cable (the overall thickness). This is often expressed in millimeters (mm).
  • Conductor insulation diameter (the actual conductor wire plus insulation thickness) and likewise this measurement is often expressed in millimeters.
  • If the cable has solid or stranded conductors
For the RJ45 connector you will need to know:
  • Cable jacket OD that the plug is capable of accepting
  • Conductor insulation diameter that the plug is capable of accepting
  • If the plug is 2 prong or 3 prong. 3 prong plugs will work with stranded and solid copper conductors. 2 prong plugs work with stranded copper only.

Wire Closeup Info

TIPNotice that I did not include “Category” as a primary factor to consider when choosing a plug.  In fact, the “Category” stated on any bag of RJ45 plugs is at best misleading except for one very specific circumstance—the manufacturer of the Ethernet cable also happens to make the connector and has fitment and performance tested the components together as a system. trueCABLE goes this extra mile, so if you select a trueCABLE Cat6 unshielded RJ45 plug you can be assured it will fit onto trueCABLE brand Cat6 unshielded Ethernet cable.  We also thoroughly document our connecting hardware so you can make an informed choice if you are not using trueCABLE brand Ethernet cable.

Are you, the consumer, being lied to? Not precisely. When a manufacturer (that only makes plugs and not the cable, for example) states a category on their plug to make selection easier, they assume the consumer is not savvy enough to choose based upon dimensions and this makes selection far more confusing! A properly documented and advertised plug would be listed as “RJ45 Plug, 3 prong for solid copper Ethernet cable, fits 7.00mm OD and 1.04mm insulated conductors.” So, what did the “XYZ Manufacturer” do? They advertised their plug as “Cat6”, leaving out the important stuff, and this leaves you guessing.

Here’s the relevant data from one of our Ethernet cable specification sheets, specifically Cat6 Unshielded Riser:

Cat6 Technical Data

So, for this cable we can see it has:

  • Solid copper conductors
  • Jacket OD of 5.90mm
  • Conductor insulation diameter of 0.96mm

Here’s the data for our Cat6 Unshielded Pass-Through Connectors:

Cat6 Pass Through RJ45 Connectors | Unshielded

The dimensions from the connector specification sheet shows it works with:

  • Cable jackets OD up to 7.10mm
  • Insulated conductor diameters from 0.95 – 1.05mm
  • Solid or stranded copper conductors

We have a match!

Good To Know & Best Practices

  • For cable insertion into the back of the connector, connectors come in three primary types:
    • Standard push-in
    • Push-in with modular load bar
    • Pass-through
  • A higher category rated connector will not necessarily be physically backward compatible with lower rated cable due to fitment differences
  • Some connectors lack a strain latch, and will require a crimp and termination tool that either lacks or has an adjustable strain latch presser bar. This is often found with large shielded connectors that also have an external ground.
  • Using a higher rated connector than your cable does not provide any additional performance benefit, but there is no harm in doing so, assuming it fits properly
  • Buy more connectors than you need. It is wise to test terminate (crimp) the connectors onto the cable to make sure you can work with them. In addition, if you make a bad crimp then you can simply use any extras. Even the most experienced installers make a bad crimp from time to time.
  • If you are new to this kind of activity, then practice as much as practical. The more terminations you make, the better you will get.
  • Different manufacturers refer to measurements differently and in either English or Metric units
  • A manufacturer might indicate their Ethernet cable has 23AWG conductors but provide no information on the conductor insulation diameter. If you cannot locate this information, then select a connector that can accept a wide range of conductor diameters such as 22AWG through 24AWG if you are using 23AWG conductor cable. This is likely a safe choice, but there are no guarantees.
  • If you do make a bad termination, then the connector is trash and cannot be reused
  • Cable strain relief boots are helpful, but entirely optional
So, now you know enough to select the proper RJ45 connector for your next Ethernet project.  Practice makes perfect, so my sincere advice is to dive right in and start putting on connectors.  You will likely make mistakes, but that is the best kind of learning.



trueCABLE presents the information on our website, including the “Cable Academy” blog and live chat support, as a service to our customers and other visitors to our website subject to our website terms and conditions. While the information on this website is about data networking and electrical issues, it is not professional advice and any reliance on such material is at your own risk.

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