Nowdays ethernet is a most common networking standard for LAN (local area network) communication, officially standardized by IEEE standard 802.3. Nowdays ethernet runs at 10Mb, 100Mb or 1Gb per second. It was originally developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus (old coaxial cable) or star topology (standard UTP cable). Most ethernet networks use unshielded twisted pair (UTP) cable. Category 5 (CAT5) cable widely used, but other variations are available. EIA/TIA specifies RJ-45 connectors - properly called 8P8C - (ISO 8877) for UTP (unshielded twisted pair) cable. (RJ45 refers to a set of connectors beyond the 8P8C standard but the former has replaced the latter in common usage).
| Pin | Name | Description |
|---|---|---|
| 1 | TX+ | Transmit Data+ |
| 2 | TX- | Transmit Data- |
| 3 | RX+ | Receive Data+ |
| 4 | n/c | Not connected |
| 5 | n/c | Not connected |
| 6 | RX- | Receive Data- |
| 7 | n/c | Not connected |
| 8 | n/c | Not connected |
Length of CAT5 cable runs should not exceed 100 meters.
Note: TX & RX are swapped on Hubs (see crossover cable). Also, please note that it is very important that a single pair be used for pins 1 and 2; 3 and 6. If not, performance will degrade.
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