Clearing up the Confusion Over RJ45 and 8P8C Connectors

 22 Jan 2012 - By Omar Yesid Mariño+

8P8C connectors, or 8 Position 8 Contact connectors, are modular connectors that are used widely within the telecommunications industry on both twisted pair and multiconductor flat cables. For a variety of reasons, they became confused with the RJ45 connector and to this day are most commonly known as RJ45s.

8P8C connectors have a variety of uses, but are most commonly used in telephony and computer networking applications, such as ISDN – you will most likely have seen them at either end of your ethernet cable. The internet has seen their production increase and their cost fall. 8P8C connectors are now commonly available from components stores and prices are incredibly low, with RS Components current selling price for the 8P8C or RJ45 connector sitting from 49p each.


So why the confusion between the 8P8C and the rarely used RJ45? The RJ45 is a registered jack standard for a modular connector using 8 conductors. It was commonly used as a connector on telephone cables, then as the internet got underway the RJ45S was designed for use with high speed modems. With broadband now leading the way, very few people use dial up modems so the real RJ45 and RJ45S connectors are seldom used today.

The confusion seems to have come in terms of appearance. As both the RJ45S and 8P8C use an 8 Position, or 8 pin, body, they appear incredibly similar. The RJ45S in fact features an extra tab that prevents it being used with other types of connector. An actual 8P8C will not work with a RJ45S socket. However, as the RJ45 came about first and telephone installers were used to using it, as the more modern 8P8C appeared they were informally referred to as RJ45s.

Decades down the line and it seems that the name has stuck, with no sign of change coming any time soon. Most components companies still sell 8P8C connectors as RJ45s. In addition, the majority of manuals for products that feature the 8P8C will refer to it as an RJ45 too.

In fact many registered jack types are commonly confused. The registered jack standard specifies the wiring pattern for a jack as well as its physical appearance, so jacks are given names based on their wiring, not their physical geometry. Many jacks appear physically very similar, leading to confusion. It’s often the case that you can’t tell precisely which standard of RJ you are dealing with until you open it up and take a look at the wiring. Wikipedia have an interesting article about this unusual naming mix up here.

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