CAT1 or Category 1 Cabling is the lowest grade of unshielded twisted-pair (UTP) cabling. Category 1 cabling was designed to support analog voice communication only. Category 1 cabling was used prior to 1983 for wiring installations of analog telephone systems, otherwise known as the Plain Old Telephone Service (POTS).
The electrical characteristics of category 1 cabling make it unsuitable for networking purposes, and it is never installed as premise wiring. Instead, all premise wiring must use either category 3 cabling, category 4 cabling, or category 5 cabling, with category 5 or enhanced category 5 cabling preferred for all new installations.
CAT1 cable is not an official category standard established by TIA/EIA. However, Category 1 has become the common name given to Level 1 cables originally defined by Anixter International, the distributor.
Cat 1 cable was typically used for networks that carry only voice traffic, for example, telephones.
Official TIA/EIA-568 standards have only been established for cables of Category 3 ratings or above.