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Fujitsu reed keyboard switches

Overview

Fujitsu produced numerous series of keyboard reed switch. The known reed switch series are FES-1/2/3, FES-4, FES-5, FES-8 and FES-9. Although the series names appear to have been mostly assigned in ascending numeric order, the DIN-compliant FES-4 was most likely the final type to be introduced. With considerable help from Kiyoto in Japan, understanding of these series has increased significantly. Some of the data comes from the Fujitsu magazine, available only in Japan and offline only. At present, no permission has successfully been obtained to reproduce any of this material, and most of it is in Japanese.

The term “FES” is common to the series names of all of Fujitsu’s keyboard switches. In 1970, the various FES types are illustrated in a photograph captioned “FES形押しボタンスイッチ外観 / Outer view of FES type pushbutton switches”, suggesting that “FES” originally denoted one specific family. The individual series were numbered FES-1 and FES-2. As later switch reed and mechanical series were introduced, their series names also carried the same FES prefix. This includes the leaf spring lower assemblies and the FES-360 discrete leaf spring and the related FES-370 non-leaf dome switch.

The switches of some of the series (FES-1, FES-8 and FES-9) were marked with the part number and what appears to be a date code or lot number. No conclusive interpretation of the date code has been reached. The codes may be production dates, arranged as the last digit of the year, then the month letter (1–9, X–Z) with optionally digits after that. However, the “X” in the corresponding code on one of the FES-8 switches is a full-width multiplication sign (“×”) instead of a Latin letter, which would be a strange mistake to make.

Series

FES-1/FES-2/FES-3

FES-1 and FES-2 is the oldest-known Fujitsu reed design, and the lowest numerically. FES-2 is the illuminated version. These switches appear to be linear only, and are extremely rare. FES-3 is related to FES-1 and FES-2, but no details about it have been discovered.

FES-5

Little is currently known of FES-5. It appears to have been introduced in 1972, and it is a tactile and clicky reed switch type specifically designed for terminals with a focus on providing good operator feedback. The single known diagram of it shows a tall switch with the reed running down the centre.

FES-8

FES-8 is described by Kiyoto as a “modernization of the specifications of FES-1/2/5 by reorganizing them”. This series offered both reed and Hall effect sensing; at present only the reed type has been encountered. This is the switch type found in N860-8282-T002 in both its tactile and linear forms. Like FES-1, it is still a tall design.

Illumination can be in the form of either an incandescent lamp (fixed to the body of the switch) or by LED, and the LED moves with the keycap to maintain consistent illumination (although an alternative LED type exists that is hard to understand from the magazine illustration). Both upstroke and downstroke damping are provided.

Two switch part numbers can be observed on the switches in model N860-8282-T002. This keyboard does have illuminated keys, but the part number for those was not documented.

Variants

Part number Variant Found in
823001 Momentary linear N860-8282-T002 (1980)
833001 Momentary tactile N860-8282-T002 (1980), Shimadzu FKB-1A

FES-9

FES-9 is a reduced-height version of FES, introduced possibly around 1977 based on a timeline chart from the Fujitsu magazine. They can be seen in MouseFan’s N860-9201-T001. (The 9000-series N860 code alone implies that these are FES-9, and they appear to be the reduced height shown in the magazine diagram.) FES-9 is the result of making a number of changes to reduce excess height, without making any drastic changes. These changes appear to include removing the “feet” from the reed carrier, shortening the base, and shortening the plunger. The switches are still damped, and seem to have the same illumination options as before.

The protrusion in the plunger in FES-8 that appears to be there to engage the tactile leaf is present in FES-9 too, suggesting that tactile FES-9 switches exist.

Variants

Part number Variant Found in
933001 Momentary tactile B06B-1430-B003A (1992)

FES-4

FES-4 is the “cross reed” type; these can be seen in the Sony OA-S3400 word processor keyboard. It is likely to have been introduced to meet German DIN standards, before being abandoned in favour of the cheaper leaf spring family. The Fujitsu timeline suggests that it was introduced in 1980, which seems a little early for a DIN-compliant product. Curiously, the series name was assigned out of sequence, using the previously unassigned FES-4 designation.

While the older reed types all mount the reed capsule vertically (as was traditional), FES-4 places it horizontally, as found in European reed switches from FR Electronics, ИЗОТ and Unitra Dolam. Like ИЗОТ reed switches, the large reed capsule is placed diagonally across the centre of the switch and extending from corner to corner, making it single-pole only (FR Electronics and Unitra Dolam reed switches use a smaller capsule that is offset to one side, permitting double-pole arrangements).