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 (10base-T), 100Mb (100Base-T) or 1Gb (1000Base-T) 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).
|1||Transmit Data+ or BiDirectional||TX+||TX+||BI_DA+|
|2||Transmit Data- or BiDirectional||TX-||TX-||BI_DA-|
|3||Receive Data+ or BiDirectional||RX+||RX+||BI_DB+|
|4||Not connected or BiDirectional||n/c||n/c||BI_DC+|
|5||Not connected or BiDirectional||n/c||n/c||BI_DC-|
|6||Receive Data- or BiDirectional||RX-||RX-||BI_DB-|
|7||Not connected or BiDirectional||n/c||n/c||BI_DD+|
|8||Not connected or BiDirectional||n/c||n/c||BI_DD-|
Length of CAT5 cable runs should not exceed 100 meters.
Please note that it is very important that a single pair be used for pins 1 and 2; 3 and 6, 4 and 5 (if used), 7 and 8 (if used) in any common straight-thru UTP Cat5 network cable. If not, performance will degrade. Also note that TX & RX should be swapped if two computers are connected without switch/hub and for connecting some devices without MDI-X autosensing (see UTP crossover cable).