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Does anyone know where I can find the specs for what each wire inside CAT 6 does? Specifically, which are for sending, and which are for receiving?

Both 100mbit and 1Gbit specs would be useful, thank you in advance...

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2 Answers 2

up vote 9 down vote accepted

What each wire in the cable does depends on how the cable is wired to the Ethernet connector. In addition, to allow straight-through cables to work, end nodes typically have transmit/receive reversed with respect to switches. Most modern devices detect this automatically anyway.

For 100-base-T, the standard for wired fast Ethernet connectors, the connector wirind is:
1 - TX+
2 - TX-
3 - RX+
6 - RX-
The remaining 4 pins are unused. Note that 1/2 form a pair and should be wired to a twisted pair in the cable. Similarly, 3/6 form a pair and should be wired to a twisted pair in the cable. A typical CAT5 or CAT6 four pair run can carry two fast Ethernet links since each only needs two pairs.

For Gigabit, it's:
1 - A+
2 - A-
3 - B+
4 - C+
5 - C-
6 - B-
7 - D+
8 - D-
The 8 pins form four bi-directional pairs. Each pair handles differential signals in both directions at all times. 1/2 form a pair, 3/6 form a pair, 4/5 form a pair, and 7/8 form a pair. Pairs must be mapped onto twisted pairs in the cable.

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Exactly the same as CAT5 - the only difference between CAT5 and CAT6 is the characteristics of the physical construction of the cable.

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1  
Yes, but I don't know those details for CAT5 either, I just used CAT6 because that's the latest implementation. –  Soviero Oct 25 '11 at 1:35

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