Copyright Goodheart-Willcox Co., Inc. 63 Chapter 2 Network Media—Copper-Core Cable specifi cations can change between applications. Th e two main cable applications are voice (low-frequency analog) and data (high-frequency digital) signals. Also, diff er- ent manufacturers sometimes post higher ratings for their cable than the minimum rating. For a complete listing of twisted-pair categories, see the chart in Figure 2-17. Note that Category 5e is not a separate category but rather an addendum to the Category 5 specifi cation. Type Maximum Frequency Rating Data Rate Number of Pairs Comments Category 1 UTP None Less than 1 Mbps 2 Used for electrical signals repre- senting voice transmission. Category 2 UTP 1 MHz 4 Mbps 4 Used in earlier networks that were limited to 4 Mbps. Category 3 UTP or STP 16 MHz 10 Mbps 16 Mbps 4 Can be found in existing networks rated at 10 Mbps and 16 Mbps and in some telephone installations. Category 4 UTP or STP 20 MHz 16 Mbps 4 This cable type was only a slight improvement over Category 3. Category 5 UTP or STP 100 MHz 100 Mbps 1000 Mbps (using 4 pairs) 4 Commonly used in 10BaseT and 100BaseTX network installations. Category 5e UTP or STP 100 MHz 100 Mbps 1000 Mbps (using 4 pairs) 4 This cable type is not a replace- ment for the Category 5 cable. It is an addendum to the cable classification. Category 6 UTP or STP 250 MHz 1 Gbps 4 Has a plastic spine used to separate the conductors. Category 6a UTP or STP 500 MHz 10 Gbps 4 Introduced AXT. Category 7 UTP or STP 600 MHz 10 Gbps 4 Each pair of twisted conductors is protected by foil shielding. Then, all four pairs are surrounded by foil or braided shielding. Category 8 STP 1800–2000 MHz 40 Gbps 4 There is no unshielded version of this cable. Figure 2-17 Twisted-pair categories and their characteristics. There are eight twisted-pair categories. Category 5e is an addendum to Category 5, not a separate category. Goodheart-Willcox Publisher Category 1 Category 1 cable is limited to low-frequency applications such as voice signals. It consists of two untwisted conductors. While this design is suffi cient for electrical signals representing voice transmission, it is inadequate for computer networks. Category 2 Category 2 cable consists of four pairs and has a maximum frequency rating of 1 MHz. It was once used in networks that were limited to 4 Mbps.