There has, for some time, been confusion over the use of the terms Category and Class to define the performance of structured cabling solutions. ANSI/TIA use Category (often abbreviated to Cat) to define both the performance of cable and components and the performance of the installed cabling. ISO/IEC, CENELEC (EN) and BSI (BS EN) use Category to define the performance of cable and components and Class to define the performance of the installed cabling. The various Categories and Classes can be summarised as follows:
It is important to note that the performance of a Cat 6 Permanent Link is not the same as that of a Class E Permanent Link, although both are rated to 250MHz and both will support the transmission of 1Gb Ethernet. The ISO/EN standards have tighter limit lines for the electrical parameters in all Classes when compared to their Category equivalent. This means that a cabling system that passes Class E will almost certainly pass Category 6 but not necessarily vice versa. The same applies to all Classes when compared to their Category equivalent.