twinax cabling

Definition of twinax cabling in The Network Encyclopedia.

What is Twinax Cabling?

Twinax cabling is a form of coaxial cabling with twin central conducting cores. Twinax cabling typically uses 20 AWG stranded copper conductors, has an outside diameter of 1/3 inch, and comes with either a polyvinyl chloride or plenum jacket. Twinax cabling typically has an impedance of 80 to 100 ohms. Twinax cabling is used primarily for connecting IBM System 3X or AS/400 systems to 5250 terminals.


To extend a twinax connection over long distances, use a repeater. Twinax repeaters can typically transmit signals up to 1 mile over unshielded twisted-pair (UTP) cabling and over longer distances using duplex fiber-optic cabling. One repeater is required at both ends of the connection.

Use a multiport repeater (hub) to connect several terminals over a single connection to an AS/400 or System 3X host. You can use twinax-to-RJ-45 baluns to connect the terminals and mainframe host to the hub by using UTP cabling. Some repeaters have RJ-11 ports for extending twinax connections over standard telephone cabling. Twinax cabling is traditionally used in a daisy-chained topology, but if you use a multiport repeater, you can also use a star topology configuration.