Category 1 cable (Cat 1) a.k.a. voice-grade copper is a misnomer, probably adopted by those who assumed that TIA set up "Categories" for all types of cables originally defined by Anixter International, the distributor, under the grades called "Levels." Cat 1 cable was used in earlier times. It was typically used for networks that carry only voice traffic, for example telephones. TIA/EIA-568 only recognized cables of Category 3 ratings or above. Anixter "Level 1" was a grade of unshielded twisted pair cabling designed for telephone communications, and was the most common on-premises wiring.
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