Registered Jack Overview

What Is a Registered Jack?

A registered jack is a standardized connection, most commonly used in telecommunications. The examples with which most people will likely be familiar are those that connect to the back of a computer, into the network card. These Ethernet cables, sometimes referred to as LAN lines or LAN connections, use an RJ45 connector to join the electrical contacts in the cable to the electrical contacts in the network card.

The standardization of the jack allows for efficiency. The jack itself is usually durable, providing a connection that can stand up to torque and other hazards. This level of protection can be enhanced with the use of accessories that make the connections more durable. Hoods, for instance, can be added to network termination points where the registered jack receives the plug. The hood, placed over the plug, allows protection for the connection, keeping out environmental hazards such as dust and moisture.

Registered jacks are the result of both technological and legal challenges. They owe their origins to the gradual collapse of the Bell System monopoly in the US and, in fact, the standard designations for modular jacks flow out of that era, when Bell started to use them on its system. Those registered jacks allowed third parties to create devices that were designed to work with Bell System lines, allowing competition for the monopoly to develop. With deregulation in the 1980s, the modular jacks became ubiquitous, as accessory manufacturers became producing devices for people’s phone lines.

As home computers because standard consumer items, another type of registered jack, RJ45, became familiar to consumers all over the world. Wider and capable of handling more connections than the RJ11 connectors used for telephones, these quickly became mainstays of both home and office and everyday people became familiar with them, as everything from routers to modems to network storage drives to computers required those consumers to understand how they work.


What Are Registered Jacks Used For?

Registered jacks are used in telecommunications applications. They are used on telephones, on data connections and, within those applications, there are many different types of registered jacks that are employed.

In very large facilities with a great deal of data and telecom equipment, it’s common for registered jacks to be organized into patch panels. Where there are data connections in buildings, there is oftentimes only one connection, usually in a wall socket, that allows connection to a data network.

Telephone lines, older designs, principally, may use a patch panel that features open connectors into which pairs of wire are punched down, but registered jacks are the standard way that any telecom device is connected to the carrier line. Hardwired phones and other telecom equipment are almost never employed anymore, owing to the convenience of registered jacks.


How Does a Registered Jack Function?

Registered jacks have to provide a connection between telecommunications device and telecommunications carriers, or data using devices and the data networks to which they are attached.

To provide this, the jack contains several different potential contact points, which is described by how the jack is named. These contact points may or may not actually have wires connected to them in a given application, and they may have different arrangement of wires for different purposes. This allows them to be used flexibly and in many different applications, even when the same type of jack is being used.

The jack’s standardized design includes a tab that retains it in the socket once it is plugged in. This provides stability for the connection and prevents it from being accidentally disconnected during normal usage.


The connectors for registered jacks are easy to install.


Who Invented Registered Jacks?

The Bell System introduced registered jacks to the world in the 1970s. This was the result of a lawsuit against them. Before registered jacks were available, many people had telephones that were hardwired into their homes. Some telephones used connectors, but they were not as efficiently designed as are registered jacks. Registered jacks provided a way for third parties to manufacture equipment that could be connected to Bell System telephones.

Today’s system of registered jacks was made more efficient by the Administrative Council for Terminal Attachments, which was created after the Bell System was broken up in the 1980s. The current designations for registered jacks have names that describe both their form and their wiring configurations and are used all over the world.


What Name Convention Do Registered Jacks Use?

The naming convention for registered jacks is referred to as the Universal Service Ordering Code (USOC). This is a standard that was born in the 1970s. The Bell System was responsible for creating it. These are still used to describe the jacks.


Which Registered Jack Types Exist? Which Type Is Used for What Application?

Registered jacks are differentiated by a numbering system, with letters added to designate certain characteristics. Some the numerical designations follow, though there are many more. The ones that follow are commonly used in households and industry.

The letters that are sometimes added to these designations include C and W, which indicate a wall that is surface mounted or a jack that is mounted in a wall, respectively. The letter S along with the name indicates that the jack is intended for one line. The letter M indicates multiple lines may be run through the jack. The letter X is used for the most complex types of jacks in multiline systems.

Other designations include A/A1. This indicates that the, on a key telephone system, the jack is connected to the hold system.

A designation of “Bridged” means that the jack has a parallel connection. T/R jacks are those that the jack connects to what are called the tip wire and the ring wire. Jacks that are used with Data connections are sometimes designated as suck. Data transmission requires better control over signal power, and these lines jacks are sophisticated enough to provide such protection.


The numerical designations include ones that are not official, RJ50, but which are in such common usage that they may as well be. In many cases, there are adapters that allow the following types of jacks to be used with equipment that has a different type of connector.


  • RJ11 Connectors


There are two primary variations of RJ11 connectors. They are both used most commonly to connect landline telephones to the telecommunications provider by way of the wall connection.


The RJ11 connector that is used in the wall is usually designated RJ11W. For connectors that are used with desk style telephones or telephones that are completely handheld units, the RJ11C designation is sued. These are 6-posiiton connectors.


  • RJ12 Connectors


These are used in key telephone systems. The RJ12 connector will carry one line of these telephone systems and are differentiated by the C and W designations, as are RJ11 connectors.


  • RJ14 Connectors


These connectors come in C and W varieties. They are able to carry two telephone lines per connection.


  • RJ22 Connectors


These connectors can carry up to 12 telephone lines. They are used with PBX systems and are usually used on systems that are provided by the telephone company.


  • RJ25 Connectors


These are used on multiline systems. They can carry up to three different telephone lines per connection.


  • RJ45 Connectors


These are very common connectors used on LANs. They are slightly wider than the familiar RJ11 registered connectors and carry one data line per connection.


  • RJ50 Connectors


This is actually not a standardized jack according to the USOC, but 10P10C connectors are commonly referred to by this name. These are used in data transmission and have 10 contacts in them, as well as 10 contact positions. These are used in a variety of applications, including radio products and controllers.


What Are Considered the Wiring Details of Registered Jacks?

In each registered jack, there are positions where contacts can potentially be made and positions where contacts area actually installed, which are often different.

Some arrangements do not use all the potential contact positions in the jacks, with RJ11 jacks being an example of this. They have two conductors that are unused in practice.

Some registered jacks are physically identical but have different contacts within them. In such cases, these jacks are usually differentiated by the number of lines that they can carry, but may actually receive the same connector.


What Are RJ Adapters, Couplers and Extensions?

Couplers are used to join two lines together. They are simple devices, generally consisting of inputs on both sides of the device, into which the two adjoining connectors are plugged.

Extensions can extend the range of a transmission over wires. They usually have a transmitter and a receiver element in them and come what many different connector options.

Adapters allow one type of connection to be joined to another. They allow, for example, an M12 socket to be used with RJ45 connections.


Which RJ Connector Accessories exist?

RJ connectors have a range of accessories available that can be used with them. These include dust caps, which are particularly vital in industrial applications when the connectors are used in dirty areas, various types of plates and mounting fixtures that allow for proper organization of the cables and many others.


What Are RJ Connector Hoods and Boots?

Hoods and boots provide a degree of protection for RJ connectors. They’re usually formed so that they cover the entirety of the device, but are easily moved back when the connector is plugged into a jack. The tabs are accessible due to the flexible materials of which the hoods and boots are made. These can greatly reinforce a jack and ensure that it doesn’t break under normal usage. They’re very common on premanufactured cables and are commonly added to custom constructed cables for their protective purposes.


What Are RJ Kits?

Working with RJ connectors requires tools that make it easy to cut, strip and connect wires for the connection. These kits usually include a cutter and a stripper in one accessory. A separate tool is used to crimp down the contacts onto the connector, providing a reliable connection precise enough for data transmission.

Some of the kids come with more advanced tools, such as testers and punches, dies and more. These are usually used by professional technicians, though simple kits are available for specific tasks, such as terminating cables, which have fewer accessories but come at a reduced cost.


What Are RJ Patch Panel Modules and Accessories?

These are parts used in high-capacity applications. Patch panel modules can be added to allow a very complex network to be connected. These panels are expandable by way of the modules, which can be added to an existing panel as needed. The organization that these panels allow are among their most desirable features.

The accessories include various jacks and cassette to plug assemblies that allow easy expansion of the panels.


What Are RJ Patch Panels?

RJ panels are used for the same purposes as any other type of patch panel. They provide a convenient way to organize many different network connections into a small space. The panels generally have ports that are numbered or otherwise marked so that they can be easily differentiated from one another and various network patches easily connected or disconnected from the network on the whole.

These panels are found in just about any network room, including small ones. Even small networks with one or two servers usually have a patch panel so that the connections can be organized and to provide protection. In very large telecom or data facilities, patch panels can be exceedingly large and complex.


What Are RJ Socket Modules and Blanks?

Socket modules are easily installed to serve as jacks for various types of connectors. They come in designs for use with Cat 5, Cat 6 and Cat 7 cabling. They can be purchased with great specificity, including the type of shielding required, the orientation, the direction, the color and more.

Faceplates and other connection accessories also fall under this category. There are also floor boxes, datacom models and many other types of connectors available.


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