ISO 70's and 80's coax and twinax terminal docs/brochures

Al Kossow aek at
Wed Sep 19 13:32:01 CDT 2018

On 9/19/18 11:08 AM, Grant Taylor via cctalk wrote:

> So would you be emulating the 3174's twinax connection and the functions it provides?  Functionally being (what I think
> is) a controller that would in turn communicate via TN3270 across the network to Hercules?


non-trivial project, but something that needs to be documented.

coax and s/3x twinax terminals are similar conceptually.

There were companies like Telex/Memorex/MTX/Visara, Decision Data and Lee Data that sold terminals in both flavors
The ones for coax talked to 'establishment controllers' that were the actual intelligence of the terminal.
The terminals themselves were essentially polled keyboards and a (80 x N line) alphanumeric display.
Later multiple simultanious mainframe sessions were added to the terminals that you could switch between.

Coax uses a point-point connection between controller and terminal, twinax is multi-drop through T connectors.
Well, sort of. Eventually both systems migrated to phone style CAT cable with coax to RJ baluns and patch panels.

There were other companies that sold serial async converters that would take the polled protocol and could turn
it into something an ASCII serial terminal could deal with.

Then PCs got things like "IRMA" cards that could pretend to be one of the polled terminals, buffering the alphanumeric
screen image on a local RAM buffer the PC could communicate with. That evolved into hardware that could support multiple
sessions as well. Same thing happened with twinax, with different vendors. 'IRMA' was a DCA/Attachmate/Microfocus thing.

The hardware got more and more integrated over time. The Telex 277 has three boards of TTL in the terminal. 276
generation used two 2901s. The last of the MTX terminals were pretty much just one National DP83445 ASIC, or one 317744
CIP ASIC in the case of Attachmate.

If you don't want real coax hardware, you just run TN3270. I'd like to have something runnable at the museum on period
hardware, though, that might be possible to maintain, which was why I picked up the Telex.

More information about the cctech mailing list