Editing IBM 3270 (section)

===Multiplexers===
IBM offered a device called 3299 that acted as a multiplexer between an accordingly configured 3274 controller, with the 9901 multiplexer feature, and up to eight displays/printers, thereby reducing the number of coax cables between the 3x74 controller and the displays/printers.

With the introduction of the 3174 controller internal or external multiplexers (3299) became mainstream as the 3174-1L controller was equipped with four multiplexed ports each supporting eight devices. The internal 3174 multiplexer card was named TMA – Terminal Multiplexer adapter 9176.

A number of vendors manufactured 3270 multiplexers before and alongside IBM including Fibronics and Adacom offering multiplexers that supported [[Twisted pair|TTP – Telephone Twisted Pair]] as an alternative to coax, and fiber-optic links between the multiplexers.

In some instances, the multiplexer worked as an "expansion" unit on smaller remote controllers including the 3174-81R / 91R, where the 3299 expanded the number of coax ports from four to eight, or the 3174-51R / 61R, where the 3299 expanded the number of coax ports from eight to 16.