http://www.hp.com/rnd/images/dia_faq_crosspic.jpg

What are the color code ?http://www.hp.com/rnd/images/dia_faq_crosspic.jpg

Could you explain to me this picture so that I could find the color code for each pin >

A picture explains it best... I would just recommend a different picture. Try this one:

http://www.netspec.com/helpdesk/wiredoc.html

From the link above:

Standard End
Pin 1 White/Orange
Pin 2 Orange
Pin 3 White/Green
Pin 4 Blue
Pin 5 White/Blue
Pin 6 Green
Pin 7 White/Brown
Pin 8 Brown

Crossover End
Pin 1 White/Green
Pin 2 Green
Pin 3 White/Orange
Pin 4 Blue
Pin 5 White/Blue
Pin 6 Orange
Pin 7 White/Brown
Pin 8 Brown

Could you also tell me the function of white/brown and blue/white ?

In a 10/100 Mb network:

Standard End (568B)
Pin 1 White/Orange (TxData +)
Pin 2 Orange (TxData -)
Pin 3 White/Green (RecvData +)
Pin 4 Blue (Unused)
Pin 5 White/Blue (Unused)
Pin 6 Green (RecvData -)
Pin 7 White/Brown (Unused)
Pin 8 Brown (Unused)

Crossover End (568A)
Pin 1 White/Green (RecvData +)
Pin 2 Green (RecvData -)
Pin 3 White/Orange (TxData +)
Pin 4 Blue (Unused)
Pin 5 White/Blue (Unused)
Pin 6 Orange (TxData -)
Pin 7 White/Brown (Unused)
Pin 8 Brown (Unused)

Notice that the send and receive are inverted.

If you are using gigabit ethernet and need those pins this should help you:
http://satyr35.ifh.de/~wischnew/baik...netcables.html

There are Bi-directional pairs A, B, C, and D

Could you also tell me how data differs in Tx/RCVData+ and the negative one ?

Basiclly the Transmit (TxData) wires send data from the computer to the rest of the network and the Receive (RxData) wires receive data from the network. The Tx- and Tx+ signals are known as a differential signal pair. An integrated chip on the network adapter combines the 2 signals back together for the receive and vice versa for transmit.

The advantage of using a differential signal pair is the signal can be transmitted over a longer distances then single ended signals and have better noise immunity. RS-232 serial data is an example of a single ended signal.

Ethernet wiring is known as UTP - Unshielded Twisted Pair. Due to the characteristics of a differential signal for most cases a shielded wire is not required. Basically the more twists per inch the faster the data can be transmitted.

The following info is for RS-422 & RS-485 but the basic theory is the same.
http://www.bb-elec.com/tech_articles...ir_signals.asp