Friday, April 2, 2010


Network cards are your up-link to the world. The PC typically uses a NIC which a CAT5 UTP/STP Ethernet cable can connect to. You may find thinnet (coaxial) ports on older NIC cards.
CAT5 means Category 5. There are two types of CAT5 cables: UTP and STP. UTP stands for unshielded twisted pair, and the maximum distance is 100m. This is the most popular cabling standard right now. The connection uses RJ-45 heads. CAT6 exists but it never really reached industry standard. Some devices may not work with CAT6 cables. The official standard is now CAT5e.

For Fiber Optics, you have multi- and single-mode fiber. Multi-mode fiber cables have a maximum distance of 275 metres to a few miles. The connection varies from FC (Ferrule Connector), SC (Subscriber Connector), LC (Lucent Cable) and so on. Multi-mode fibers are typically easier to work with. Single-mode fibers are harder to work with and more fragile, but is able to reach many many miles. Some single-mode fiber cables can reach across states.

There are 8 wires in a UTP. Only 4 wires are in use for typical connections. Cables are stripped then crimped to a RJ-45 connector. The wires must be arranged into a standard. There are two standards: T568-A and T568-B. The more popular standard is T568-B. The order is as follows for T568-A:
1) Green Stripe
2) Green
3) Orange Stripe
4) Blue
5) Blue Stripe
6) Orange
7) Red Stripe
8) Red

For T568-B, it is:
1) Orange Stripe
2) Orange
3) Green Stripe
4) Blue
5) Blue Stripe
6) Green
7) Red Stripe
8) Red

To create a straight-through cable, both sides should be either T568-A or T568-B. To create a cross-over cable, simply use T568-A on one side and T568-B on the other. To know which cable to use, we must categorize devices into two groups.

DTE (Data Terminal Equipment):

DCE (Data Communications Equipment):

When a DTE connects to a DCE, a straight-through cable is used. When a DTE connects to a DTE, a cross-over cable is used.

A patch panel is a layer 1 equipment that typically terminates wall jacks from office cubicles. From the other end of the patch panel, patch wires (shorter UTP cables) are used to connect the ports to switches or other things.

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