Mike's PBX Cookbook

RJ45 Cabling Tips

1 What does T568A and T568B mean, and how are they different?

T568A and T568B are the two wiring standards for 4-pair data cable specified by TIA/EIA-568. The only difference is the position of the orange and green wire pairs. T568B is preferred, and should be used wherever possible. A "crossover" cable has A at one end, and B at the other.

Pin #
1 White/Orange
2 Orange/White
3 White/Green
4 Blue/White
5 White/Blue
6 Green/White
7 White/Brown
8 Brown/White
Pin #
1 White/Green
2 Green/White
3 White/Orange
4 Blue/White
5 White/Blue
6 Orange/White
7 White/Brown
8 Brown/White

2 What does RJ stands for?

RJ stands for Registered Jack. It is a standard, regulated by the FCC, defining the connector and wiring for connecting network equipment (telephone and data). A dash is not needed before the number, but often used. Registered jacks, include:

3 What is the Category Rating System?

The category rating system grades cable bandwidth performance. It applies only to 100 ohm UTP and STP wiring systems.

CategoryTIA/EIA StandardDescription
1NonePOTS, ISDN and doorbell wiring
2None4 Mbps token ring networks
3TIA/EIA 568-B10 Mbps Ethernet - frequency up to 16MHz
4None16 Mbps token ring networks - frequency up to 20MHz
5None100 Mbps Ethernet - frequency up to 100 MHz
Not suitable for GigE (1000BaseT)
5eTIA/EIA 568-B100 Mbps & GigE Ethernet - frequency up to 100 MHz
6TIA/EIA 568-B2x Performance of Cat 5 & 5e - frequency up to 250 MHz
6aNoneFuture specification for 10Gbps application
7ISO/IEC 11801 Class FDesigned for transmission at frequencies up to 600 MHz

4What is UTP and STP cable?

UTP stands for Unshielded Twisted Pair, a cabling system with one or more pairs of twisted insulated copper wires contained in a single sheath. It is the most widely used cabling system in telecommunications and data communications environment today.

STP stands for Shielded Twisted Pair, where an outer covering or shield is added to the ordinary twisted pair cable. The shield functions as a ground, and reduces the potential for electromagnetic interference, allowing for higher transmission rates.

5Tips For Installing Category Cables

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