deskthority

A bunch of keyboard types from the Mitsumi 1998 catalogue are low profile (ca. 7 to 11 mm as I recall) and they all offer something interesting:

"Mounting the chip diode on membrane (MITSUMI's own technology) has come to solve the problem of the N-key rollover which is indispensable for personal computers"

(I don't know if a single PDF exists of the whole catalogue, but I'll add some more datasheets from it at some point to [wiki]Category:Mitsumi catalogues and brochures[/wiki] that cover these strange series.

I've never seen any evidence of this being done, but apparently it's possible! The keyboards themselves are not scissor, but just low-profile rubber dome over membrane.

I don't know any actual keyboard models though, but that specific quote is for KHK Type (spring over dome, hysteresis), and it's a taller 15.3 mm design.

I wonder if I have not seen an old post of such a keyboard ...

I do also faintly recall a Fujitsu Siemens keyboard that had the controller not on a PCB but mounted on the membrane itself. It may have been the split ergo that was also marketed as the Kinesis Maxim.

I did come across a Mitsumi split ergonomic keyboard (I don't have the details to hand), although I see that the Maxim has keycaps that fit with Fujitsu Siemens styling.

I remembered last night that I looked at the keyboard of a Macintosh PowerBook 150, and the keyboard to that was rubber dome but not scissor, rather like what Mitsumi show in the diagrams for all their low-profile switch types. Maybe Mitsumi made it. The rubber in that PowerMac keyboard was too stiff to type on and the machine got recycled a few years ago as the video controller was fried.

The pictures in the PDFs show laptop keyboards, but by 1998 when these PDFs were made, it seems surprising that you'd have non-scissor laptop keyboards, or anyone who cared about putting NKRO into a laptop. All very odd.

The Mitsumi ergo is a custom KFK Type — basically it's the standard GoldTouch ergonomic keyboard (※この製品はGoldtouch technology Inc.社向けのOEM製品です。 — Original equipment manufacturer product by Goldtouch technology Inc). KFK Type is not advertised as having diodes on the membrane.