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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
2000 3.8 mm ? 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
Function keys 2.5 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
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.