Category 3 cable

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Category 3 cable, commonly known as Cat 3 or station wire, and less commonly known as VG or voice-grade[1] (as, for example, in 100BaseVG), is an unshielded twisted pair (UTP) cable used in telephone wiring. It is part of a family of standards defined jointly by the Electronic Industries Alliance (EIA) and the Telecommunications Industry Association (TIA) and published in TIA/EIA-568-B.[2][3]

Although designed to reliably carry data up to 10 Mbit/s,[4] modern data networks run at much higher speeds, and Cat 5e or better cable is generally used for new installations.[5] Cat 3 cables may have 2, 3 or 4 pairs.[6]


Cat 3 was widely used in computer networking in the early 1990s for 10BASE-T Ethernet and, to a much 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.[7] In some use cases and for short distances, Cat 3 may be capable of carrying 100BASE-TX (2 pairs) or even 1000BASE-T (4 pairs). Such use cases include hobbyist retrofitting short home telephone Cat 3 networks for Ethernet.[8][9][10]

Dedicated 100BASE-T4 networks, supporting 100 Mbit/s over Cat 3, appear to have been a rarity as very few network interface controllers and switches were ever released. Some examples include the 3com 3C250-T4 Superstack II HUB 100, IBM 8225 Fast Ethernet Stackable Hub[11] and Intel LinkBuilder FMS 100 T4.[12][13] The same applies to network interface controller cards. Bridging 100BASE-T4 with 100BASE-TX required additional network equipment.


Starting in the mid-1990s, new structured cabling installations were often 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 have policies that any upgrade to a network using Cat 3 must involve upgrading to Cat 5e.[14]

See also[edit]


  1. ^ CompTIA Network+ Review Guide: Exam N10-008. John Wiley & Sons. 28 September 2021. ISBN 978-1-119-80696-7.
  2. ^ Evolution of Cabling Standards: TIA/EIA, ISO/IEC, CENELEC[self-published source?]
  3. ^ Standards Update[self-published source?]
  4. ^ "CCNA: Network Media Types". Cisco Systems. Retrieved 2017-09-05.
  5. ^ Spurgeon, Charles E (2000). Ethernet: the definitive guide. O'Reilly. p. 125. ISBN 9781565929524.
  6. ^ Williams, Lawrence (2020-03-01). "Ethernet Cables Types: Cat 3, 5, 5e, 6, 6a, 7, 8 Wires Explained". Retrieved 2023-04-09.
  7. ^ IEEE 802.3at-2009, clause 33.1.1c
  8. ^ Gigabit over Cat3, WTF[self-published source?]
  10. ^ How to convert your telephone line to an internet line: A complete guide[self-published source?]
  11. ^ IBM 8225 Fast Ethernet Stackable Hub
  12. ^ "3Com Product End of Sale dates" (PDF). Hewlett Packard Enterprise.
  13. ^ "Intel Express 100BASE-T4 User's Manual". Manualzz.
  14. ^ "University of Wisconsin – Standards for the Installation of New Data/Voice Jacks". Retrieved 2013-09-17.

External links[edit]