RJ45 isn't really RJ45

Some interesting trivia for your Saturday: the ubiquitous network cabling plug best known as RJ45 has been living a lie. Technically speaking, the RJ45 designation actually refers to a registered jack, a telecommunications standard which defines both the mechanical interface (plug) and the wiring scheme used to terminate a cable. The modular connector itself is officially designated 8P8C (8 positions, 8 contacts), while the wiring standards used to terminate twisted-pair cabling are defined in TIA/EIA-568-A and B.

So why the mix-up? One can assume that the telco RJ nomenclature was subconsciously carried over to the network world by cable plant installers when twisted-pair LANs started gaining popularity in the late eighties and early nineties, and the terminology has simply stuck ever since.