Network connection

usually a network cable uses two out of four pairs of wires, one for transmit the other for receive.

a normal cable connects PIN 1+2 on one side to PIN 1+2 on the other side, and PIN 3+6 to PIN 3+6.

a crossover cable connects PIN 1+2 to PIN 3+6, and PIN 3+6 to PIN 1+2.