Category 3 cable

Category 3 cable, commonly known as Cat 3 or station wire, and less commonly known as VG or voice-grade (as, for example, in 100BaseVG), is an unshielded twisted pair (UTP) cable used in telephone wiring.

It is part of a family of copper cabling standards defined jointly by the Electronic Industries Alliance and the Telecommunications Industry Association and defined in TIA/EIA-568-B. Although designed to reliably carry data up to 10 Mbit/s, modern data networks run at much higher speeds, and Cat 5e or Cat 6 is now used for all new installations - and many large institutions require any repairs or additions to existing buildings that currently use Cat 3 to be upgraded to Cat 5e.

Cat 3 was widely used in computer networking in the early 1990s for 10BASE-T Ethernet (and to a lesser extent for 100BaseVG Ethernet, token ring and 100BASE-T4), but from the early 2000s new structured cable installations were almost invariably built with the higher performing Cat 5e or Cat 6 cable required by 100BASE-TX.

The original Power over Ethernet specification supports the use of Cat 3 cable, but the new 802.3at Type 2 high-power variation does not.

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