SNKB-M2017-BT4-122
| Full Name | Unicomp PC 122 5250 Terminal Emulator |
| Part NumberPart Number The number used to describe this keyboard's specific release; usually specific for a target region, language or SKU, etc. |
UB40T56 |
| TypeType A designation from my own type naming scheme used to categorise this keyboard with or from others by their common features and market intent but may/may not be derived from official names. |
Model M Type IV 122-key Host Connected Converged Keyboard |
| NicknameNickname A [keyboard enthusiast] community given name for this keyboard. It can be a shortening of its name and properties, a more abstract term, a real-life reference, or metonymy. |
Battlecruiser |
| Key-switchesKey-switches The name of the known switching mechanism that lies under this keyboard's keys. |
IBM membrane buckling springs |
| Original KeycapsOriginal Keycaps The keyboard's original keycaps' material and text/symbol printing technique. |
PBT with dye-sublimated legends |
| FeetFeet The style of this keyboard's flip-out or extendable feet. If applicable, this may also state how many levels of height adjustment are available and whether the feet could be rubberised. |
Single-setting elongated flip-out feet |
| ProtocolProtocol The protocol(s) this keyboard can use to speak to the host computer (eg, scancode sets). |
IBM Mode 2 (scancode set 2) |
| ConnectionConnection The keyboard-to-host connection. This is could be a description of a cable (its colour, whether its coiled, whether its detachable, and what connector is at its end) or the name of a wireless technology. |
Black straightened-style fixed 6-pin mini-DIN PS/2 cable |
| Form FactorForm Factor The standardised or universally acknowledged name for this keyboard's layout form factor. |
120% |
| Production Date | 2017-04-05 |
| Acquisition Date | 2022-07-08 |
About this keyboard type
Officially the IBM Personal System/2 Host Connected Keyboard, the Type 4 122-key Model M was a variant of the Type 3 Converged Keyboard intended for terminal emulation on IBM PS/2 personal computers. It wasn't designed with a specific PS/2 model in mind, instead, it was available as an option for any IBM PS/2 or later series model that qualified for IBM's Select-A-Keyboard scheme. Select-A-Keyboard allowed customers to choose from a variety of keyboards for their qualifying system at the time of purchase for no additional charge. Select-A-Keyboard and the PS/2 Host Connected Keyboard were both announced in June 1991 but production of these keyboards started at least a year earlier. Lexmark later produced its own self-branded version. Type 4 remains in production today as the Unicomp Emulator 122 (continuation of the professional host-connected keyboard) and PC 122 (a more consumer-orientated keyboard), produced under their own branding or for third-party thin client brands such as 10ZiG Technology, Affirmative Computer Products, BOS/BOScom, Development Concepts, Inc., I-O Corporation and NLynx Technologies.
Type 4 "M122s" are at their core just a specialised version of the Type 3 Converged Keyboard with PC compatibility, so it's considered a terminal emulator keyboard rather than simply a terminal keyboard that most of its predecessors were. The keyboard's design is for the most part identical and is still considered a "battlecruiser" or "battlecruiser-sized" keyboard by enthusiasts. But to reflect their nature as a dual-purpose keyboard, Type 4s also have at least two-colour dye-sublimated legends to differentiate PC-only functions (usually in blue) and terminal/universal functions (in black). Being a Converged Keyboard at their core, they have their recognisable top 24-key and lefthand side 10-key function key banks. The legends on the 24-key bank were generally "Fxx" nomenclature for 3270 or 5250-style keyboards. IBM and Lexmark branded variants were always intended for IBM 3270 emulation, but 5250-orientated versions are known for third-party branded Type 4s. All Type 4 "M122s" currently discovered use a typewriter-style layout with no data entry style version yet found.
The best way to tell IBM-branded Type 3s and 4s apart is the latter's presence of lock-light LEDs in the top-right corner of the keyboard. Unicomp-made keyboards can have or lack these lights though, so in such cases, the two-colour legends on the keycaps can also be used to differentiate them. Like Type 3s, they have the distinct Model M wedge shape profile, (originally) oval-shaped IBM branding, slim bezels between the keys and the side edges, a small surface area around the 24-key bank's raised platform, and a three-way cable router on the bottom cover (though many Type 4 cables don't fit the longer channels). Type 4 "M122s" originally ditched attached cables in favour of removable SDL to PS/2 cables that IBM Enhanced and Space Saving Keyboards famously used. Unicomp later supplemented and replaced them with attached cables terminating in an AT-style DIN, PS/2 or Type-A USB plug. Type 4s were made of PVC during the IBM days, but Unicomp has since switched to using PC+ABS. Unicomp also introduced raven black-coloured versions of the Type 4, which today is now the standard option. Like Type 3, Type 4 "M122s" never had the DIP switches some of their predecessors could have. Quiet Touch rubber dome versions of Type 4 have been available since Unicomp took over production.
