The naming confusion of RJ45

There was originally only the true telephone RJ45. It was one of the many registered jacks, such as RJ11, which was a standard from which it gets the RJ in its name. As a registered jack, the true telephone RJ45 specifies both the physical connector as well as wiring pattern. The true telephone RJ45 uses a special keyed 8P2C modular connector with Pins 5 and 4 wired for tip and ring of a single telephone line while Pins 7 and 8 connected to a programming resistor. When they found similar-looking connectors were being used in non-telephone applications, like connecting computers, they called these ‘RJ45′.
But the problem was that the physical connectors indicated by the true telephone RJ45 were not compatible with computer RJ45 connectors. The true telephone RJ45 connectors are a special variant of 8P2C, which means that only the middle 2 positions have conductors in them. Computer RJ45 is 8P8C and in them, the all eight conductors are present. True telephone RJ45 involves a keyed variety of the 8P body, which means it can have an extra tab, which a computer RJ45 connector is unable to mate with.
As the true telephone RJ45 never saw wide usage and the computer RJ45 has wide used today, computer RJ45 stands for always, that a person is referring to when they say RJ45.
Rounding out the confusion regarding the RJ45 naming, it is the fact that some people intend to encompass not just the connector shape and size, but also the wiring standard for it described by TIA/EIA-568-B.

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