The Truth Behind Modular Plugs

Modular Plugs from Clear Polycarbonate

Many people think that modular plugs are just modular plugs but they’re wrong. If you have had a computer for a long time, then you probably have experienced problems that were extremely difficult to resolve. In most cases, the flaky problem usually means that a cable has gone bad or was poor quality to begin with.

Modular Connectors Also Known As:

Many companies use other names for modular plugs. These include:

  • Modular phone jack
  • Modular connector
  • RJ connector
  • Western jack/plug

Use of Modular Connectors

Originally patented by Bell Telephone Laboratories in 1975 for telephone wiring, these modular connectors are now used for many other purposes including Ethernet jacks. Modular plugs have replaced bulkier, more expensive connectors used in networking applications.

Bell Telephone Laboratories


Connectors have gender. This can get extremely tricky but all you need to remember is: male connectors are called plugs and female connectors are called jacks or sockets.

Most plugs are males, includes headphones, keyboards, mouses, etc. If the plug has prongs or pins, then the plug is male.

Male plugs are used to terminate loose cables while female jacks are used for fixed locations on surfaces (receptacles). In other words, appliances have cords ending in a “male” plug, which is fitted into the “female” outlet.

Types of Plugs

Bodies– Great modular plugs are made of clear polycarbonate. There are two lengths of bodies: short and long. In the US and Canada, RJ-11/12 plugs are short bodies and RJ-45/48 plugs are long bodies. Make sure any plug you buy have long latches which are levers used to release the modular plug from the sockets.

Short Body - RJ-11/12

Long-Body RJ-45/48






Body Size – Many of our readers are confused by what the differences between RJ-11, RJ-12, RJ-22, RJ-45, and RJ-48  are. Its easy. Here we go:

-RJ-11 and RJ-12 bodies are exactly the same size bodies. The only difference is the number of contact blades. RJ-11 has 4 and RJ-12 has 6 contact blades. (RJ-11 can be substituted with RJ-12 but not RJ-12 for RJ-11.)

-RJ-22 handset modular plugs are narrower than RJ-11 and RJ-12 bodies. RJ-22 are used for coiled handset telephone cords.

-RJ-45 and RJ-48 bodies are exactly the same and are long bodies. RJ-45 have 8 contact blades while RJ-48 have 10.


Left: 2-Prong; Right: 3-Prong

Modular plugs come with either 2-prong or 3-prong blades. 3-prong blades are the BEST contact blades you can buy and generally found only on high-quality modular plugs. They hold the wire in the modular plug more efficiently than the 2-prong blades. 3-prongs are designed to be used with either stranded, solid or modular wires. On the contrary, 2-prong blades have different blades for solid, stranded and modular. For solid wire modular plugs, 2-prong blades have chiseled sides to the blades, where stranded wire modular plugs do not.

Don’t be fooled by manufacturers who make straight blades with three slits in them. These are counterfeit 3-prong blades and do not work well.

Blade Plating

Modular plug blades are made of either phosphor bronze or just bronze and most contact blades have 24 carat gold plating. You should purchase phosphor bronze blades. The best contact blades have 100 microns of nickel under-plating over the phosphor bronze. Next comes the 50 microns of 99% pure 24 carat gold over-plating.

Don’t be fooled: Some companies try to cheat you by using poor grade nickel plating or no nickel plating at all. These companies will also try to use cheaper grades of gold while still charging a premium. Gold plating does double the price of modular plugs, but the few extra cents is worth the assurance that you will not have problems later on. Flaky contact problems are some of the most difficult and most expensive problems to debug.

Amount of Plating

To determine the amount of gold plating you need, you must determine how many times you will connect and disconnect the modular plugs before the gold plating wears off. Once the gold plating is gone, your network connection will have problems transmitting signals correctly. The higher the number of microns, the longer your gold plates will last.

Don’t be fooled: Some suppliers will avoid mentioning the amount of gold plating or lie about the amount of gold plating in the contact blade. When the amount is not mentioned, the gold plating is usually 3 microns or less. The maximum amount of gold plating is 50 microns. Please do not be fooled when suppliers say they have more than 50 microns of gold plating. ITS FALSE!

Average modular plugs get plugged and unplugged 250 times! That is why 50 microns of gold should be the only standard that you accept.

Below are the number of connections and disconnections that each amount of gold plating can handle:

Plating                  Number of Connects/Disconnects

Flash (<3 microns)                5 Connects

3 Microns                            35 Connects

6 Microns                            65 Connects

15 Microns                         165 Connects

30 Microns                         325 Connects

50 Microns                         550 Connects



RJ connectors are frequently terminated using the T568A or T568B pin/pair assignment that are defined in TIA/EIA-568B. A cable that is wired as T568A at one end and T568B at the other is a “crossover cable.” Crossover cables are used to connect two devices without a switch or a hub. A cable wired the same at both ends is called a “patch” or “straight-through” cable. These cables need a hub or switch to connect to.

T568A Wiring


T568B Wiring


Wikipedia – Modular Connectors

eHow – The Difference Between the Male & Female Connectors on a Computer

Male Connector

Modular Plugs

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15 comments for “The Truth Behind Modular Plugs

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    Enjoy the fresh appear. I really enjoyed the content. Thanks a lot for this helpful write.

  2. Kevin J
    February 6, 2012 at 3:56 pm

    Would like to add for Wireless cabling connectivity some female connectors have pins.

    For this application, the key thing to remember is that male connectors have nuts (in order to tighten the connection).
    -Kevin J

  3. Joe
    February 6, 2012 at 7:34 pm

    Thanks for the post and extra information!

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