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 (EIA) and the Telecommunications Industry Association (TIA) and published in TIA/EIA-568-B.
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. The original Power over Ethernet 802.3af specification supports the use of Cat 3 cable, but the later 802.3at Type 2 high-power variation does not.
Starting in the mid-1990s, new structured cabling installations were almost invariably built with the higher performing Cat 5e cable required by 100BASE-TX. Cat 5e or Cat 6 is now used for all modern structured cabling installations. Many large institutions which require any repairs or additions to existing buildings that currently use Cat 3 have policies requiring upgrade to Cat 5e.