The RJ system was originally invented by AT&T and Bell Labs in the 60’s . The idea was to design a standard interface that could be used throughout the United States and the world when dealing with different instruments. The RJ45 jack was originally designed for the AT&T telephone system often called the Merlin System in the 70’s and 80’s. All other phone systems used the RJ11 jack which is considerably smaller and only uses 3 pairs of wires and is called a six position jack. The RJ45 is an eight position jack and in telecommunications terminology it is often called a 4-pair jack. The RJ45 is now primarily used for Ethernet over copper twisted pair wire computer network systems. When used in the Ethernet system, it will support all the categories from category 3 up through and beyond category 6. Each jack has to be rated for the category of it’s intended use in the network design. In other words, if you have cat6 cable and patch panels, you must use cat6 RJ45’s. The RJ45 also can be used with shielded cable. In that case, the jack itself is surrounded in a metal case that must be grounded. Using shielded cable and shielded jacks together insure the highest protection from radio waves. This type of cabling system is unusual and rarely used. An application would be for use near a strong radio station or equipment that sometimes transmits in the radio frequencies. Some government organizations also use shielded twisted pair and shielded jacks for use in a secure network.

Crimping RJ45’s

When using RJ45 mod plugs to make patch cords, make sure that the mod plug matches the type of cable on the patch cord. Some patch cord cables come with braided wires and other cable that is used for patch cords is solid copper wire. It is hard to distinguish just by looking at the mod plug whether or not the mod plug is designed to be crimped on solid or stranded cable. Also if you use a stranded RJ45 mod plug to crimp onto a solid copper wire, you will run into problems within 3 years. That is the time that it takes for the crimped mod plug metallic service to form tarnish on the copper portions of the wire and mod plug. This tarnish build up will cause resistance in the line and introduce problems in the network. Therefore it is my recommendation that you always buy patch cords that are made by a professional manufacturing company rather than making patch cords yourself.

RJ45’s and VoIP Pin Outs

There are 2 types of pin outs for an RJ45 Ethernet computer network. One is a 586a and the other is a 586b. It does not matter what pin out system you use as long as you use the same standard throughout the network. If you start with a 586b, always use 586b throughout your cabling system. 586a is usually used by the military or the government and 586b is commonly used by commercial or business organizations. Needless to say, whatever standard you use, keep it consistent and you will not have any problems in your network.

Voice over IP also known as VoIP always uses RJ45’s cabled according to Ethernet standards. There is no distinction between VoIP traffic and computer traffic when it comes to computer cabling. VoIP will work fine on cat3 standard and above but it is recommended that you use cat5e or above.