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 standards defined jointly by the Electronic Industries Alliance (EIA) and the Telecommunications Industry Association (TIA) and published in TIA/EIA-568-B.[1][2]

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

Networking

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.[6] 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.[7][8][9]

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[10] and Intel LinkBuilder FMS 100 T4.[11][12] The same applies to network interface controller cards. Bridging 100BASE-T4 with 100BASE-TX required additional network equipment.

Replacement

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.[13]

See also

References
  1. Evolution of Cabling Standards: TIA/EIA, ISO/IEC, CENELEC
  2. Standards Update
  3. "CCNA: Network Media Types". Cisco Systems. Retrieved 2017-09-05.
  4. Spurgeon, Charles E (2000). Ethernet: the definitive guide. O'Reilly. p. 125. ISBN 9781565929524.
  5. Williams, Lawrence (2020-03-01). "Ethernet Cables Types: Cat 3, 5, 5e, 6, 6a, 7, 8 Wires Explained". www.guru99.com. Retrieved 2023-04-09.
  6. IEEE 802.3at-2009, clause 33.1.1c
  7. Gigabit over Cat3, WTF
  8. CONVERTING HOME TELEPHONE WIRING TO ETHERNET
  9. How to convert your telephone line to an internet line: A complete guide
  10. IBM 8225 Fast Ethernet Stackable Hub
  11. "3Com Product End of Sale dates" (PDF). Hewlett Packard Enterprise.
  12. "Intel Express 100BASE-T4 User's Manual". Manualzz.
  13. "University of Wisconsin – Standards for the Installation of New Data/Voice Jacks". Retrieved 2013-09-17.
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