February 9, 2013

How to wire ethernet cables – Part 1

Ethernet – the most popular & widely used network standard has grown ever since it was started way back in 1970s by Xerox Corporation.The Institute of Electrical and Electronics Engineers (IEEE) is responsible for the specification popularly known as Ethernet. Though IEEE rarely refer it as Ethernet. It is referred as 802.x series of standards after its initial release in 1985. The Ethernet standard  define different approaches for a network’s physical layer and methods which define how computers share a network.

A popular configuration for networked PCs & embedded systems follows the specification for the 10BASE-T media system in the Ethernet standard. A 10BASE-T network uses twisted-pair cables with a network speed of 10 Mb/s. With the advancement of technology this speed has been increased to 100 Mb/s & 1000 Mb/s. Twisted pair cable can not only carry signals over long distances but are also inexpensive. Because of twisting the size of magnetic field emanated from wires is reduced and also it helps to cancel any noise that wires pickup due to magnetic coupling.

Ethernet CAT5e cable

IEEE has also standardized the type of cables to be used for different kind of networks. Cable that meets the Category 5e specification defined in EIA/TIA-568-B can be used for all the three different speeds. A Category 5e cable contains four unshielded twisted pairs (UTPs) of wires. Each pair consists of two insulated conductors that are twisted, around each other, with about one to three twists per inch. The number of twists per inch helps to reduce noise in the wires. The wire diameter is generally 24 or 22 AWG. An outer layer of insulation surrounds the pairs.

The wires in the twisted-pair cables are color-coded  with a color (blue, orange, green, or brown) assigned to each twisted pair. One wire in the pair is  white with colored stripes and the other fully colored. The usual connectors for twisted-pair Ethernet are RJ-45 plugs and jacks.

Ethernet cable twisted pairs exposed

Today we will see how you can your self wire Ethernet cables for your home or office network systems.There are two common pin outs for the RJ-45 connectors used with twisted-pair cable: T568A and T568B . Though you can go for either of standards, the TIA/EIA-568-B but recommends T568A. The pin outs of both standards are as under –

Numbering system as per T568A standard

The only difference between the two pin outs is the color of the wires at the pins. With T568A, pins 1 and 2 are the green pair and pins 3 and 6 are the orange pair, while with T568B, pins 1 and 2 are the orange pair and pins 3 and 6 are the green pair.

Just keep in mind that whatever standards you follow, both the ends of cable
should have same pinout but if you want crossover cable, make one end pinout as
T568A and the other one as T568B.

Here is how the RJ45 plug looks exposing metal pins before crimping the cable.

RJ45 plug

Detail view of metal pins’ pointed ends that pierce the wire coating to make contacts.

RJ45 plug close up showing metal pins

Another view of RJ45 plug.

Ethernet connector RJ45 plug close up

View of RJ45 Jack which is soldered to Printed Circuit Board ( PCB). The one on the left is having 2 LEDs – Green & Yellow to show line activity. While other has no LEDs.

Ethernet Jacks with LEDs and without LEDs

RJ-45 jacks showing pins for soldering.

View of RJ45 Jacks from below.

In the next part we will see the tools available to crimp the cable to RJ45 plug.

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