Category 3 cable

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

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. 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.

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