The cross-over cable comes in handy when you want to connect two computers together using Ethernet cable but without a Hub. Other uses include connecting devices using Full Duplex Ethernet. The two most common standards of cable configurations are the T568A and the T568B.
These wiring diagrams conform to the EIA/TIA-T568B modular wiring configuration (also called AT&T specification, previously called 258A)
This picture shows the orange wire terminating at pin number one with the clip pointing down and the pins pointing up. Notice how short the wiring is cut to ensure that the wires are untwisted as little as possible. This is Called a Modular Plug. What it goes into is called a Jack.
This configuration is to utilize all four pairs of 8 pin twisted pair telephone cabling. TX technology only utilizes 2 pairs. Pairs 1,2 and 3,6. T4 technology uses all 4 pairs. For conformity you should ALWAYS utilize all available wires.
The twisting of the wires is very important. To ensure Category 5 transmission performance do not untwist paired wires more than 1/2 inch (12.7mm).