Mitsumi rubber dome keyboards

Mitsumi offered a range of rubber dome and buckling rubber sleeve types, many of which were targeted at notebook computers. Many of these offered N-key rollover in the form of “Mounting the chip diode on membrane”, something that has yet to be explained or observed.

Height is measured from the bottom of the backing plate to the middle of a keycap. All types have a bounce time of 10 milliseconds. See Mitsumi catalogues and brochures on the Deskthority wiki for archived copies of all the catalogue pages used as the source material for this data.

Series	Spec.	Keys	Travel	Height	Form	Weight	Lifetime	NKRO
KEK	1998	All	2 mm	8.2 mm	Rubber dome	50 gf	10 M	No
KEK		All	2000	3.8 mm	Rubber dome	?	10 M	55 gf	No
KEL	1998	All	3 mm	9.42 mm	Rubber dome	50 gf	10 M	Yes
KFK	2001	All	4.2 mm	?	Rubber dome	50 gf	10 M	No
KGL	2000	All	2.8 mm	5.8 mm	Non-cross scissor	50 gf	10 M	No
		2003	Normal keys	3.0 mm			6.1 mm		10 M
		2003	Function keys	2.5 mm			6.1 mm		5 M
KHK	1998	All	3.5±0.5mm	13.5 mm	Spring over rubber dome with hysteresis	60±20 gf	10 M	Yes
KUJ	1998	All	1.5 mm	7.5 mm	Buckling rubber sleeve	50 gf	10 M	Yes
KUK			2 mm	9 mm
KUL			3 mm	10 mm
KUL			3 mm						11 mm

Documented examples of Mitsumi notebook keyboards are extremely scarce. An unidentified example exists with buckling rubber sleeve switches; these could be one of KUJ/KUL/KUL, but all those types have the raised areas front and back relative to the keys, instead of to the side. The keyboard was not opened up, so it is not possible to see whether it has “chip diodes” on the membranes.