A type of cabling that is specified in ANSI/EIA/TIA 568, and ISO/IEC 11801. Originally developed in support of 16 Mbps IBM Token Ring LANs, Cat 4 is an orphaned category. Cat 4 runs over 24 AWG unshielded twisted pair (UTP) and is rated at 20 MHz. In ISO/IEC 11801 terms, Cat 4 falls into Class D ( 100 MHz). See also AWG, LAN, Token Ring, and UTP. 10/100Base-T LAN, 155 Mbps ATM, 1000Base-T (Gigabit Ethernet, or GbE) POTS, ISDN BRI, RS-232 & RS-422, low-speed data, speaker wire, alarm cable Unspecified; < 1 MHz.