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Omron B3G-S series

Here follows a few notes on Omron B3G-S series. These relate to discussions with Sandy in 2015.

Specification

In addition to a B3G catalogue page, I also received a B3G-S catalogue page (from a catalogue reportedly dated “1986/7”) from Omron via Quest Components:

This page begins, assuming I’ve transcribed it correctly:

形B3G-Sフルキーボード用キースイッチ(口一プ口フィール形)
DIN規格に適した全18.1mmのロープロタイプ

Of the Google, Bing and Excite translation websites, Google offers by far the best translation, of:

Form B3G-S full keyboard for key switch (mouth one flop opening feel-shaped)
Low-profile type of all 18.1 mm suitable for DIN standard

The claim appears to be that the two-finger leaf contact is intended to achieve comparable reliability to non-contact switch technology. (This two-finger contact approach was previously introduced by companies such as Marquardt and Mitsumi.)

Something I had not noticed previously, is that the switch is specifically noted as being DIN-compliant, which is likely to be one of the reasons for the redesign.

Until the whole document is transcribed and translated by someone who reads Japanese (as the scan resolution is so low that the characters are partially obliterated), here a couple of notes:

The page above only covers B3G-S100, B3G-S200 and B3G-S400. B3G-S300, which was not retained in B3G-S*N, is notably absent, and this possibly represents the latching variant, since Sandy notes that the later design no longer supports the latching guide frame. The higher numbers listed below (500 to 700) are also not covered.

The second digit covers “LEDスポット照光” (the presence of an integrated LED), being 0 (no LED), 1 (赤, red LED), or 2 (緑, green LED). For example, B3G-S220 would be S200 with a green LED.

“Flat” switches

“Flat” is Sandy’s nickname for the original design of B3G-S switch: the slider is a plain rectangle with notches in the corners, as seen on the 1986 catalogue page:

View full-size image “Flat” design (depicted: latching)
View full-size image “Non-flat” design (depicted: tactile with no-LED base)

“Flat” switches are extremely rare, but two dated examples have been found so far, one from 1985 and one from 1987 (out of only four known instances of these switches). Sandy also possesses two latching “flat” switches (found in an NEC 8313-12 keyboard, and depicted by his photograph above), something not seen in the later design. (We are theorising that as the redesign did not allow for a latching mechanism, those few customers still requiring latching switches would continue to receive custom batches of the original design; latching switches at this stage were seldom used outside of Apple, who were not an Omron customer.)

“Non-flat” is familiar design of B3G-S where the front and back of the slider have cut-away recesses, and the opening in the switch shell has slits at the front and back: the front and back of the slider/opening design was modified to be similar to the sides of the slider and opening of Alps SKCL/SKCM switches.

Sadly, neither of us have yet determined more sensible names for these two design characteristics!

Changes

The history of B3G-S remains poorly understood. We know that in 1988, Omron issued PRDN 495, listing the part number correspondence between B3G-S and B3G-S*N. This occurred around the time that “flat” appears to have been superseded with “non-flat”.

The document is summarised thus:

メカキースイッチ形B3G-Sシリーズの一部中止のお知らせ
メカキースイッチ形B3G-Sシリーズの一部を生産中止します。

Translation:

Announcement of discontinuation of some mechanical key switch type B3G-S Series
A part of the mechanical key switch type B3G-S series will stop production.

The part replacement table (“生産中止機種と代替機種”) is given thus, with translations in parentheses:

生産中止機種
Discontinued model
代替機種
Alternative model
形B3G-S100シリーズ (B3G-S100 Series) 形B3G-S100Nシリーズ (B3G-S100N Series)
形B3G-S200シリーズ (B3G-S200 Series) 形B3G-S200Nシリーズ (B3G-S200N Series)
形B3G-S300シリーズ (B3G-S300 Series) 特殊対応 (Special handling)
形B3G-S400シリーズ (B3G-S400 Series) 形B3G-S600Nシリーズ (B3G-S600N Series)
形B3G-S500シリーズ (B3G-S500 Series) 代替機種なし (No alternative model)
形B3G-S600シリーズ (B3G-S600 Series) 形B3G-S600Nシリーズ (B3G-S600N Series)
形B3G-S700シリーズ (B3G-S700 Series) 形B3G-S700Nシリーズ (B3G-S700N Series)

*外形寸法・仕様規格値の変更はありません。 / * Dimensions and specifications there is no change of the standard value.

The document also notes that “Manufacturing propriety of old products” is “impossible”.

So far, no documentation has been found that indicates what modification to the switch necessitated the change in part numbers, and whether this change occurred at the same time that the slider design was updated. A number of changes occurred around this time, including the removal of “JAPAN” from the switch shell, suggesting that the tooling had been shipped abroad. However, this occurred after the redesign from “flat” to “non-flat”, as the latter was seen briefly with “JAPAN” marking.

With Cherry and M4/5/6/7, the part numbers for switches were changed a number of times for no known reason, and M9 switches had generations with different part numbers, so there is no reason to believe that the change to “N” part numbers required any visible change.

More dated examples of keyboards might give us better insight into this enigmatic switch series.