KBK update for Wednesday, 27th November
One of the 80 pages of Fujitsu literature that Kiyoto shared with me contained a curious diagram, depicting three “snap-action” switches side by side in cross-section view. From left to right, these are:
- A tall switch captioned “富士通” (“Fujitsu”) which is their FES-5 clicky reed switch
- IBM beam spring drawn at half its actual height
- A mystery switch
The captions for the other illustrations are illegible due to the photocopy quality. However, the third one bore a surprising resemblance to Micro Switch SD Series alternate action (per one of the charts that Honeywell sent me). This implied that the tactile SD types use a sprung pin arrangement. As I have acquired a couple of 11A1A tactile switches from Radwell, I inspected them with a torch to see just what was inside. Previously I had not observed anything of interest, but now I could clearly see a small brown pin (seemingly plastic) that retracts when the tactile point is overcome.
SD Series is an early tactile type, with the chart date being 1976-09-20. It has already been shown that Fujitsu FES-8 reed/Hall switches offered a tactile leaf as early as 1976, and it is now clear that SD Series did not offer such a design. Micro Switch SW Series also had a rare tactile type (made for IBM) and the internals of that are not yet understood.
(And yes, it is now fully confirmed that FES-8 offered Hall sensing as well as reed, with the idea being that normal keys would be reed to save power and offer high reliability, while “functional keys” would be Hall in order to drive ICs directly, presumably by virtue of being bounce-free.)
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