A data cable is the copper cable forming the permanent link from the floor distributor to the work area outlet. It consists of four twisted pairs, each twisted at a specific rate to suppress crosstalk from neighbouring pairs. Permanent links use solid conductors, commonly 23 AWG or 24 AWG; a thicker conductor gives both lower resistance and better thermal behaviour under PoE.
Category determines the frequency the link can carry. Cat6 is the 1 Gigabit Ethernet standard at 250 MHz and supports 10 Gigabit up to about 55 metres. Cat6A offers 500 MHz, carries 10 Gigabit across the full 100 metres and has a thicker construction that controls alien crosstalk. In Cat7 S/FTP each pair is foiled individually and the cable is braided overall, for industrial and high-interference environments.
Screening is decided by environment. U/UTP is sufficient in normal offices, easy to install and needs no bonding. F/UTP adds a single foil over the pairs. S/FTP foils each pair and adds an overall braid. In screened systems, end-to-end screen continuity and correct bonding are mandatory; a half-finished screen can perform worse than unscreened cable.
Jacket type follows the fire requirements of the installation. LS0H emits little smoke and no halogens, and is expected in enclosed buildings such as offices, hospitals, schools and hotels. Outdoor routes use UV-resistant PE, while underground and mechanically exposed runs use armoured constructions. Cable is supplied on 305 m or 500 m reels.
Standards cap a copper channel at 100 metres: 90 metres of permanent link plus 10 metres of patch cords. The limit comes from signal attenuation and cannot be stretched; beyond it the link fails certification and speed drops.