pin du rj45

Ethernet 10/100/1000Base-T Straight Thru

Wiring scheme: EIA/TIA 568B
This cable will work with 10Base-T, 100Base-TX and 1000Base-T and is used to connect a network interface card to a hub or network outlet. These cables are sometimes called "whips".
Note: While 10BaseT and 100Base-TX only uses two pairs, please do connect all pairs since 1000BaseT uses all of them, and save yourself some future debugging :)

Pinout

RJ45 MALE CONNECTOR to network interface card.

RJ45 MALE CONNECTOR to hub.

Name	Pin			Cable Color	Pin	Name
TX+	1			White/Orange	1	TX+
TX-	2			Orange	2	TX-
RX+	3			White/Green	3	RX+
	4			Blue	4
	5			White/Blue	5
RX-	6			Green	6	RX-
	7			White/Brown	7
	8			Brown	8

Note: It's important that each pair is kept as a pair. TX+ & TX- must be in the pair, and RX+ & RX- must together in another pair. (Just as the table above shows).
Just for your information, this is how the pairs are named:

Pair	Pins	Common color
1	4 & 5	Blue
2	1 & 2	Orange
3	3 & 6	Green
4	7 & 8	Brown

The + side of each pair is called the "tip" and the - side is called the "ring", a reference to old telephone connectors.

Pin No.	Signal Description	Abbr.	DTE	DCE
1	DCE Ready, Ring Indicator	DSR/RI	«—	—»
2	Received Line Signal Detector	DCD	«—	—»
3	DTE Ready	DTR	—»	«—
4	Signal Ground	SG
5	Received Data	RxD	«—	—»
6	Transmitted Data	TxD	—»	«—
7	Clear To Send	CTS	«—	—»
8	Request To Send	RTS	—»	«—

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This is made possible because of the wasteful (some may say "spare") wires in cat-5 cable.

Cat 5 cable and RJ-45 jacks have eight wires.
Ethernet uses two pairs (four wires), one for send and one for receive.