Computer network modular connectors and telephone registered jacks

Computer network modular connectors and telephone registered jacksThe plastic plugs on the ends of telephone wiring and computer cables are defined by various technical standards. Because these standards are full of technical definitions and acronyms, it is easy to see how street slang becomes the accepted definition for many of the plastic plugs.

It is important to understand that connecting devices together is more than just matching up connector ends on a piece of wire. Just because you can find an adapter to make your cable fit into a connection is no guarantee that the device will communicate on your network. Some connectors that look exactly alike could have different wiring configuration.

In the world of technology street slang, or common buzzwords, often become the accepted the description of something rather than the specific technology standard. For example describing Ethernet patch cables as using RJ45 connectors illustrates one of the most mis-used terms in the world of technology.

We will do our best to break down some of the buzzwords and jargon to help you understand the differences in the terms.

Modular connectors

A modular connector is an electrical connector that was originally designed for use in telephone wiring, but has since been used for many other purposes. Many applications that originally used a bulkier, more expensive connector have converted to modular connectors. Probably the most well known applications of modular connectors are for telephone jacks and for Ethernet jacks, both of which are nearly always modular connectors.

Modular connectors are designated with two numbers that represent the quantity of positions and contacts, for example the 8P8C modular plug represents a plug with having eight positions and eight contacts.

Do not assume that connectors that look the same are wired the same. Contact assignments, or pin outs, vary by application. Telephone network connections are standardized by registered jack numbers, and Ethernet over twisted pair is specified by the TIA/EIA-568 standard.

Telephone industry Registered Jack

A Registered Jack (RJ) is a wiring standard for connecting voice and data equipment to a service provided by a telephone company. In some wiring definitions you will see references to the Local Exchange Carrier (LEC), which is a regulatory term in telecommunications for the local telephone company.

Registration interfaces were created by the Bell System under a 1976 Federal Communications Commission (FCC) order for the standard interconnection between telephone company equipment and customer premises equipment. They were defined in Part 68 of the FCC rules (47 C.F.R. Part 68) governing the direct connection of Terminal Equipment (TE) to the Public Switched Telephone Network (PSTN).

Connectors using the distinction Registered Jack (RJ) describe a standardized telecommunication network interface. The RJ designations only pertain to the wiring of the jack, it is common, but not strictly correct, to refer to an unwired plug by any of these names.

For example, RJ11 is a standardized jack using a 6P2C (6 position 2 contact) modular connectors, commonly used for single line telephone systems. You will often see telephone cables with four wires used for common analog telephone referred to as RJ11 cables. Technically speaking RJ14 is a configuration for two lines using a six-position four-conductor (6P4C) modular jack

RJ45 is a standard jack once specified for modem or data interfaces using a mechanically-keyed variation of the 8P8C (8 position 8 contact) body. Although commonly referred to as an RJ45 in the context of Ethernet and category 5 cables, it is incorrect to refer to a generic 8P8C connector as an RJ45.

Why is a Ethernet eight-pin modular connector (8P8C) not an RJ45?

Both twisted pair cabling used for Ethernet and the telecommunications RJ45 use the 8P8C (Eight Position, Eight Contact) connector, and there lies the confusion and the misuse of the terms. The 8P8C modular connector is often called RJ45 after a telephone industry standard. Although commonly referred to as an RJ45 in the context of Ethernet and Category 5 cables, it is incorrect to refer to a generic 8P8C connector as an RJ45

The 8P8C modular connector is often called RJ45 after a telephone industry standard defined in FCC Part 68. The Ethernet standard is different from the telephone standard, TIA-568 is a set of telecommunications standards from the Telecommunications Industry Association (TIA). Standards T568A and T568B are the pin - pair assignments for eight-conductor 100-ohm balanced twisted pair cabling to 8P8C (8 position 8 contact) modular connectors.

How does a RJ45 to RJ11 converter work?

There is no such thing as a RJ45 to RJ11 converter. They are two different types of connectors for two totally different standards of communication. Cables with various pin configurations and wire pairs are created for specific purposes. Be careful when looking to "convert" on type of wire into another. An adapter that allows you to connect an RJ11 plug into an RJ45 plug is not converting anything.

Technically speaking neither RJ11 or RJ45 is a computer networking standard. Many times when people are looking to convert between RJ11 and RJ45 they are dealing with a device made for a two wire phone line and trying to connect it to an Ethernet eight-pin (8P8C) unshielded twisted-pair (UTP) modular connectors.

I see many questions on internet forums asking about various adapters and converters. Just because you can convert a plug from one type to another does not mean that the signal traveling along the wire will work as you expect. I can not stress enough the importance of not using any type of adapters and converters without knowing the exact wiring configuration of the devices you are trying to connect.

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