Fujitsu reed keyboard switches
Fujitsu produced at least three series of keyboard reed switch. The known reed switch series are FES-5, FES-8 and FES-9 and FES-4. FES-5, FES-9 and FES-4 are all illustrated in the Fujitsu magazine from May 1985 (page 429). Kiyoto has acquired a fresh copy of the relevant pages, but the reproduction quality is poor and almost all of the kanji are illegible to anyone who cannot read Japanese. Only descriptions in katakana are relatively readable (some knowledge of katakana is still helpful).
Figure 5 “Development of keyboard switches” (named in both Japanese and English) shows that reed keyboard switches were introduced in the early 1970s. These were initially the tall FES-5 switches. Medium-height FES-8 switches were introduced in the mid-to-late 1970s. This was followed by FES-4 around the start of the 1980s. FES-4 is captioned 「ロープロファイル」 (“low-profile”), which is assumed to indicate a redesign targeted at DIN compliance; this is the so-called “cross reed” type. (The other two types are captioned in kanji and the captions are unreadable.)
Some further details are given on Kiyoto’s Fujitsu keyboard timeline page.
FES-5 is the first known reed switch type. It is a very tall switch, and the reed appear to run down the centre inside the return spring. It does not appear to use normal keycaps. It was used in some kind of Japanese typewriter; the illustration of the from the magazine on page 428 of the keytboard in question is too poorly reproduced to recognise.
FES-8 is not depicted in the Fujitsu magazine. It is omitted from the switch illustration, but it is grouped together with FES-9 in the keyboard diagram. On the basis that FES-8 is used in N860-8* models, FES-9 is used in N860-9* models and FES-4 is used in N860-4* models (as suggested by Kiyoto), then this would make FES-8 the tall reed switch modules found in N860-8282-T002.
FES-9 appears to be a shorter version of FES-8. No external photos of FES-9 are known to exist, but from the diagram in the magazine, it is a shorter design than the switches in N860-8282-T002. Reed switches are shown in N860-9201-T001 that are assumed to be FES-9 (from the N860 code) but no complete switches are depicted. FES-9 would appear to not be a major re-design: it seems to be 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.
FES-4 is the “cross reed” type. It is likely to have been introduced to meet German DIN standards, before being abandoned in favour of the cheaper leaf spring family. While FES-5, FES-8 and FES-9 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).