Mitsumi KBH
KBH is an unclear keyboard type from Mitsumi Electric. The only details known are from an advertisement in JEE (Journal of Electronic Engineering) from 1975, where the following text can be extricated from Google Books:
Mechanical keyboard switch equals performance of reed switchesMitsumi Electric of Tokyo has recently marketed a new high-performance mechanical keyboard switch of sealed-contact design. Designated the KBH Film Type, it has a guaranteed service life of five million operations. With gold contact point in a film-sealed housing, this keyboard switch is completely immune to environmental influence, so aging and contact wear are minimized. Other features are minimal contact bounce (less than three milliseconds); and easy key operations with a long stroke of four millimeters.
KBH is illustrated within the advertisement, but Google Books ruins all attempts to observe the illustration of the switch itself.
A KBH code appears on the switch PCB of the Burroughs C3247, manufactured around 1976, but the switches found in that calculator are the same series as that used for Shift Lock on the Commodore 64. It is possible that there was an unsealed version of KBH. It is also possible that the unsealed version used a different series name, and was used as a substitute for KBH in the C3247. Further details are required before either type can be properly identified.
Japanese patent S56-107419A “Switch substrate and method of manufacturing same” filed in 1980 depicts a switch assembly that would fit the description for KBH Film Type. The contact assembly is very similar to that of Futaba MD, and is placed above the same PCB arrangement as the unsealed switches. Such a switch design would fulfil the description in JEE and it could be made physically compatible with the unsealed type. The patent for Futaba MD itself was filed years after it was introduced, so the filing date does not disprove that this design represents KBH Film Type.