Twinax cable

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Twinax cable is a cable specified for the IBM 5250 terminals and printers, which are used with IBM's midrange hosts, which are currently AS/400 (Application System 400) minicomputers (which are now called iSeries or i5), and also with its predecessors, such as the S/36. The data transmission is half-duplex, balanced transmission, at 1 Mbit/s, on a single shielded, 110 Ω twisted pair. ^[1]

With Twinax you can address seven devices, from workstation address 0 to WSA 6. The devices do not have to be sequential.

When using straight Twinax cables you can go up to 5,000 feet or 1 mile (1.6 km). Twinax is a bus topology that requires termination to function properly. Most Twinax T-connectors have an automatic termination feature. For use in buildings wired with Category 3 or higher twisted pair there are Baluns that convert twinax to twisted pair and hubs that convert from a bus topology to a star topology.

Twinax was designed by IBM as an replacement for RS-232 dumb terminals. Its main advantages were high speed (1Mbit/s versus 9600 bit/s) and multiple addressable devices per connection. The main disadvantage was the requirement for proprietary Twinax cabling.

NEC Astra system also uses this kind of cable for networking.