Registered Jack-45

What Does Registered Jack-45 Mean?

Registered jack-45 (RJ45) refers to a cable termination specification that specifies physical male and female connectors and the pin assignments of wires-in telephone cables and other networks that use RJ45 connections.


RJ45 connections are also known as data jacks.

Techopedia Explains Registered Jack-45

Registered jack-45 (RJ45) is an eight-wire connector used to connect computers on local area networks. They were initially used as a telephone-only standard, but have since been applied to high-speed modems and other computer networks.

The RJ-45 is often confused with the 8P8C standard which looks almost identical but has particular properties regarding signal loss as the cabling is always made up of twisted pairs, a noise cancelling technology. The most common confusion is where RJ-45 is thought to be the same as an Ethernet connector, which is actually an RJ45S (or 8P8C) connection. RJ-45 is a telephony specification and although the connectors are almost identical to 8P8C, they have different signal conduction characteristics.

The 8P8C standard connectors are commonly referred to as RJ-45S.


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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.