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Views: 1641 Author: Site Editor Publish Time: 13-02-2020 Origin: Site
Let’s start with RJ45, perhaps the term most widely used to refer to Ethernet cables today. RJ stands for “registered jack,” and the true RJ45 connector was originally developed as part of the standardized telecommunication network interface for the purpose of connecting telephone networks. The connectors of the RJ platform were developed as much smaller and cheaper replacements to the older telephone installation methods of hardwired cords or bulky plugs.
With the advent of computer networking, a new but very similar connector was developed to carry out data transfer: 8P8C.
8P8C refers to the array of pins, hence the name Eight Position, Eight Contact. In 8P8C connectors, each plug has eight positions that are spaced approximately 1 mm apart. Individual wires are then inserted into these positions. There are a variety of 8P8C connectors out there, with the modern RJ45 Ethernet connector being the most prevalent.
As a result of the close similarities, “RJ45” became the designated informal misnomer for any eight-pinned jack (8P8C modular connector) used in computer networking (Ethernet).
The differences between 8P8C connectors and RJ45 connectors are shown in the following diagram:
The connectors are not entirely compatible with one another because of the keying used in RJ45; 8P8C connectors can plug into RJ45 receptacles, but the inverse is not true. However, because the connectors resemble each other so closely in appearance, the groups and individuals who transitioned from telephone networking to computer networking started to mistakenly call the unkeyed 8P8C connectors “RJ45s” and the terminology quickly caught on.
Therefore, what most of the industry refers to as RJ45 connectors are in fact 8P8C modular connectors.
Today, almost all electronic equipment using 8P8C connectors will show documentation for RJ45 connectors, which is technically incorrect. This mistaken use of terminology is widespread throughout the industry, and though it is unlikely to change anytime soon, there really isn’t much reason for concern; nearly everyone is collectively making the same mistake, and those who are in the know more often than not simply use RJ45 to avoid confusion or argument.
An example of this is clearly visible in the “RJ45” Ethernet connectors. There are two RJ45 pinouts (T568A and T568B), and even though they are technically 8P8C connectors, it is very likely you will hear them strictly referred to as RJ45 connectors, and all documentation surrounding them will use the same terminology. As such, for the sake of clarity, we will refer to them as modern RJ45 connectors.
Two standard RJ45 pinouts define the arrangement of the individual eight wires needed when attaching connectors to a cable: the T568A and T568B standards. Both follow a convention of coating individual wires in one of five colors (brown, green, orange, blue, or white) with certain stripe and solid combinations.
Following either the T568A or T568B convention is essential when you build your own cables to ensure electrical compatibility with other equipment. If you don't build your own cables, you only need to verify the correct standard for use with your equipment. For historical reasons, T568B is the more popular standard, although some homes use the T568A version. The table below summarizes this color coding of the wires in the connectors.
Pin | T568B | T568A |
1 | white with orange stripe | white with green stripe |
2 | orange | green |
3 | white with green stripe | white with orange stripe |
4 | blue | blue |
5 | white with blue stripe | white with blue stripe |
6 | green | orange |
7 | white with brown stripe | white with brown stripe |
8 | brown | brown |
Several other kinds of connectors closely resemble RJ45s, and they can be easily confused with one another. The RJ11 connectors used with telephone cables, for example, use six-position connectors rather than eight position connectors, making them slightly narrower than RJ45 connectors. Other than that, they look very much the same.
RJ45 connectors come with some problems. To form a tight connection between the plug and the network port, some RJ45 plugs make use of a small, bendable piece of plastic called a tab. The tab creates a tighter seal between a cable and a port on insertion, requiring downward pressure on the tab to unplug it. The tab prevents a cable from accidentally coming loose. These tabs easily break when bent backward, which happens when the connector snags on another cable, clothing, or other nearby objects.
Most RJ45 connector problems occur when the wires don't follow the prescribed standard. People who prefer to work on their own cables and connectors must pay close attention to the proper wiring sequence to avoid problems.
