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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 they mostly appear to have been introduced in 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 Fujitu 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.

Series

FES-1/FES-2/FES-3

FES-1 and FES-2 were documented in the Fujitsu magazine in 1970. FES-2 is the illuminated version of FES-1, and appears to be designed for control panels rather than keyboards. Both series were available in momentary and alternate action forms, and FES-2 also appears to been sold in indicator form (lamp only, with no reed capsule fitted). These are tall reed switches, with a plastic shell and a metal plate retention clip. The dual-prong sheet metal keycap mount is very similar to that of IBM beam spring.

These switches were rediscovered by UncleFan when he found keyboard N860-1131-T010 for sale on Taobao Idle Fish, and Kiyoto found that it had previously been posted to the Baidu forum. The FES-1 switch designation was hypothesised from the keyboard model and later confirmed. The keyboard itself is from November 1984.

The meaning of the markings on the switches is unclear. The numbers “121954” on the switches and while the metal retaining clips are marked “121957” on the retention clips may be part numbers; they correspond broadly with the markings of “823001” (linear) and “833001” (tactile) in model N860-8282-T002 with FES-8 switches. The other 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.

FES-3 is mentioned in a 1979 article; an exploded illustration of FES-1 is captioned simply “適用製品名:FES-1,2,3形押釦スイッチ” (“Applicable product name: FES-1, 2, 3 pushbutton switch”) and no other mention of FES is made.

FES-5

Little is currently known of FES-5. It appears to have been introduced in 1975, 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.

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.

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).