Earlier this week, I made an IBM keyboard ID guide aimed at terminal keyboards of the 3101, 3270 and 5250 compatible families! The goal was to satisfy some requests I got on how to identify what family of terminal a given keyboard belonged to. I've also seen a few examples of mid-'80s and '90s terminals of one family paired with keyboards from another. Thus, I thought this would be a good thing to cover!
Link: https://sharktastica.co.uk/topics/3101-3270-5250_diffs
I state tips on how to spot the differences between 3101, 3270 and 5250 keyboards, which is generally easy/obvious for the earlier beam spring keyboards but less so for later Model F and Model M keyboards. For those, I break down how you can tell each family apart by the layout of the navigation cluster and the numeric keypad. I'll summarise a TLDR below, but the page linked above will provide more background and cover a lot more nuance in the later sections.
Feedback is of course appreciated!
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Summary
The IBM 3101 ASCII Display System, 3270 Information Display System and 5250 Information Display System were three major product families that originated in the 1970s that possessed many terminals from the '70s, '80s and '90s. Compatible/emulating terminals, thin clients and software are still available today, and thus some IBM-compatible terminal keyboards are still under production via Unicomp. I talk about three self-defined 'eras' of IBM terminal keyboards under these families.
Model B(eam spring) era
- model_bs.png (1.93 MiB) Viewed 3388 times
The original terminals of each family used beam spring keyboards. Thankfully, IBM introduced unique keyboard designs for each, thus they're easily recognisable and my page doesn't dwell on them for too long. They can be identified by a combination of their overall shape, the columns of separated keys on the left, and [if applicable] if their keypad is joined to the alphanumeric keys. The fact they're so unique is probably a major reason why people in the community generally refer to beam spring keyboards by their terminal type numbers (like "3101" and [imprecisely] "3276" and "3278") instead of generic names like "F122" or "unsaver" for Model Fs.
"Early" Model F era
- model_fs.png (928.08 KiB) Viewed 3388 times
When Model F was introduced, it seemed the practice of a unique keyboard design per terminal would be continued. The IBMs 3104, 3178 and 5291/5292 seemed to portray this. Although as evidenced by the low-profile keyboard replacement for IBM 3101, shared assembly design was already being toyed with. Still, I point out an obvious way to ID each.
"Late" Model F/Model M era
- model_ms.png (2.2 MiB) Viewed 3388 times
The introduction of the 104-key Model F ("unsaver") in March 1983 and 122-key Model F in October 1983 planted the seeds of a new paradigm where the keyboard assemblies for many different terminals would now be shared, with only what's printed on the keycaps changing. The introduction of the Model M Enhanced Keyboard and 122-key Model M in 1985 only bolstered this, and the current 3270 and 5250 keyboard offerings from Unicomp still reflect this. One keyboard design can take on many functional layouts. As such, I spend a bit more time detailing how to differentiate them apart.
- By what's printed on the back (an obvious one, but literally searching up a part number should give you an answer)
- By "navigation cluster" layout
- By numeric keypad layout
Example comparisons:
- nav_cluster.png (194.88 KiB) Viewed 3388 times
- num_pad.png (864.75 KiB) Viewed 3388 times
