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Updates for 2019


Sunday, 13th October

Wednesday, 9th October

Further rummaging has led to the rediscovery of an ITW patent that helps differentiate two of the early ferrite core types. Re-reading the patents page has led to matching up the patent that goes with the double-action ferrite core switches in the HP 9845 workstation keyboard. Understanding of Licon/Cortron/ITW’s ferrite core product range is getting slowly clearer.

Tuesday, 8th October

It seems that I forgot to post a link to the utility model for Omron “Alps-style” switches. The utility model was filed in 1988, giving a rough idea of when these switches were introduced. Sadly there is still no sign of a series name for them.

Sunday, 6th October

At the same time that Bitsavers uploaded the Electronic Engineer magazine keyboard guide, they also uploaded two Cherry data entry keyboard brochures from 1971, which are now the oldest documents to date on Cherry keyboards. These documents offer two very interesting findings:

  1. It was already known that Cherry filed a reed switch patent in 1970. These Cherry reed switches are now confirmed from official documentation. Only two models are known: 201-0100 (SPST-NO) and 202-0100 (DPST-NO).
  2. The documents also confirm that Cherry M6 started off with different part numbers. UncleFan already found a Cherry sample card demonstrating this, and this too is now confirmed from official literature. The reed switches were assigned 20x codes, while the gold crosspoint switches were assigned 26x codes, where x denotes the number of poles. Within two years, the “2” would change to “M” for the gold crosspoint switches, and the reed switches would disappear.

Saturday, 5th October

I discovered on Friday that, in July, Bitsavers scanned in a guide to keyboard technology, published by Electronic Engineer magazine in 1971 in conjunction with Micro Switch. This guide has some interesting definitions of switch types.

Depicted in that document is a mercury switch, that is clearly a Mercutronic type from Mechanical Enterprises. After discovering that the all the archive scans of Electronics Australia were removed from americanradiohistory.com for copyright reasons, I went looking to see where it had gone, and found one more mention of Mercutron(ic)¹ that I missed: a depiction in Computerworld—also from 1971—of the exact same switch (complete with the external return spring and base missing from the other diagram), along with its model: MC-210. This implies MC series.

¹ both “Mercutron” and “Mercutronic” can appear together …


Saturday, 28th September

Deepak Kandepet found an Alps calculator keypad on eBay, with PCB code CH34149B. The switches are the type that resembles spring bridge but with a metal top, but the PCB code begins “CH”. This demonstrates that “CH” PCB codes are not specific to the series that became KCC. This suggests that “SCH” is not an older name for KCC, but instead a classification code for mechanical switches. This new theory all depends on what contact type is inside SCK switches, because the theory would indicate that these are neither mechanical nor reed.


Saturday, 31st August

Curiously, it seems that there were at least three designs of Clare-Pendar S820 switch. Characteristically dreadful photos of the third type to be discovered are now posted. After revisiting the S820 and S880 catalogue page provided by Terry Trumbull of Electro-Mech, it seems that this third design is that which is depicted in the photograph in the catalogue. As the catalogue page was scanned in 1 bit per pixel, all detail is lost from the photograph, but it does appear to have the diagonally-placed retention clips of this third design.

Although S820 is nominally 2.5 oz, the example in question is significantly lower in force than a Micro Switch SD Series 2.5 oz switch. As expected for a reed switch, it is smooth, and noticeably smoother than SD Series.

Tuesday, 27th August

It seems that the plunger colours for Micro Switch SW Series non-illuminated switches may finally be understood. The original plungers were grey (ca. 1968–1971) followed by black when the plungers were redesigned. Around the mid-70s, the momentary switches were then colour-coded by sensor type: red for sink level, blue for sink pulse, and seemingly green for source level. The last one based on the assumption that “C”-type SN switches are source level, thus green-plunger SW switches with the same sensor type (per the switch bills of materials) should also be source level.

The pale red switches sometimes seen are just red switches, which for some reason can either be a vivid red, or a soft red.

Wednesday, 14th August

Series 7 is not Series 7 after all.

With the help of the fantastic staff at the Smithsonian Libraries (Christine and Trina), we have traced the reed switches to Series KB. For purposes of maximum historical confusion, these switches have an alphabetic series name but part numbers as though the series name was numeric.

By the 1973 Manual Switches catalogue, details on the keyboard switches were very cursory, likely because in keyboard applications they were long superseded by SW Series keyboards and switches.

As for SW Series, one of the last remaining anomalies is 1SW12-BL, which has been M demonstrated to be tactile. That must be what “BL” denotes. Sadly this is not in any of the recovered 1SW Series charts.

Saturday, 10th August

A new, dedicated page on Micro Switch 1SW200 Series, with the first photos of the SW Series bi-level (double action) switches.

Thursday, 8th August

Finally my Micro Switch SW Series models 1SW201-R and 1SW204-R switches arrived from the US. These are exactly what I hoped they would be: the elusive “bi-level” (double-action types). Double action in SW Series is achieved not with two sensors, but with a larger sensor IC with two Hall elements integrated. The stage two springs are attached to the plunger and protrude down from it, making contact with the switch mounting frame.

The sensor in these switches is type “U”.

Tuesday, 6th August

All evidence now indicates that the switches used in Micro Switch RW Series keyboards are Micro Switch Series 7 [Micro Switch Series KB]. Micro Switch produced a number of switch series with numeric series names, with Series 2, Series 3, Series 4 and Series 6 being confirmed. The catalogue listing numbers of all these series follow the same pattern: the series number, then a classification letter, followed by additional letters and numbers. Series 7 appears to be a derivative of Series 3; both series use the same rail mount system. Like Series 7, Series 3 comprises both reed and non-reed types. Series 7 switches came in a variety of configurations, of which not all were suitable for keyboards, pointing to the series not being specifically intended for data entry keyboards.

Additionally, the keycaps for Micro Switch SW and SN Series and Micro Switch SD Series have been found to be 2SW Series. Although not confirmed by literature, all keycap part numbers appear to fit into this subseries, including those of illuminated switches.

Monday, 5th August

Two years after receiving it in 2017, I have finally scanned in the complete George Risk Industries keyboards and switches catalogue that they sent me via Chaldon International in the UK.


Sunday, 28th July

Micro Switch PB8* keyboard switches are starting to make sense now. The difference between 1PB877 and 1PB878 (as found in Univac keyboards) is now clear: the former is one-shot and the latter is continuous. This exactly corresponds to the use of pulse and level switches in SW and SD Hall effect keyboards. While some PB types are electronically one-shot using an attached PCB, one-shot PB8* keyboard switches mechanically release the internal microswitch immediately after operation. The reason is not known, but it may be the same as with the Hall effect keyboards: a way to achieve N-key rollover.

Friday, 26th July

It turns out that there were at least three series of Digitran metal leaf capacitive switches. These are now collated on a new Digitran page. It also appears that Digitran’s metal leaf capacitive keyboards preceded those of Cortron by several years.

Saturday, 20th July

Wednesday, 10th July

The ITW, Cortron and Licon page is updated with a list of Cortron and Licon keyboards and their part numbers, which clearly follow patterns.

Friday, 5th July

The National Museum of American History Library were so kind as to provided scanned copies of the two Micro Switch SW documents in their collection:

As a result of the growing amount of data on SW and SN Series, the SW/SN page is now split up:

The National Museum of American History Library has been inducted into the newly-opened Keyboard Hall of Fame.


Monday, 24th June

Edward Walsh is now consigned to the Keyboard Hall of Shame. All the sites run by people who don’t permit you to contact them get tiresome in themselves, but even more so when they hold knowledge that was never made available properly and they don’t let you enquire about it.

Saturday, 22nd June

While digging around for more Micro Switch information, I came across an article in Modern Data from December 1970 for Licon Series 550 keyboards and switches. This was the first time observing an official term for one of their products. Cortron themselves suggested some series names (although they have yet confirmed them from their literature), one being “55”. Further digging shows FC2500 to be another official term, which appears to be their DIN-compliant ferrite core keyboards, that eventually transferred to Devlin.

A brief page is now up on ITW, Corton and Licon with all notes so far.

Monday, 10th June

I am still working my way through Micro Switch’s keyswitch product range with the help of Honeywell. It’s now clear that SN Series comprised three subseries: 11SN (snap-in panel mount, both illuminated and non-illuminated), 101SN (self-adhesive PCB mount) and 201SN (illuminated version of 101SN). A list of 11SN Series types is up, with charts to follow once I have had time to redact them, as they are all engineering charts. These details may offer some insight into SW Series keyboard switches, which were intimately related to SN Series.

Sunday, 2nd June

UncleFan has rescued me from a blunder of Japanese translation. I misinterpreted Omron PRDN 389 as being a list of switch models, thinking that “キーボード形” meant “switch types suitable for keyboards” on the basis that all the part numbers began B2C, B2H or B2R.

He has since found Omron B2R-84E2L-602, and it is a keyboard, not a switch. Therefore, PRDN 389 is a list of discontinued keyboards, and now all the codes listed make far more sense! All the strange numbers in the middle are of course just the number of keys, analogous to how Micro Switch numbered their keyboards, using the same series names for switches and keyboards.

Saturday, 1st June

Based on all the charts from Honeywell, the Micro Switch SD Series page is extensively updated with all new details on the series.


Thursday, 30th May

Another jackpot! This time, Honeywell have turned up 13 charts from SD Series, dating the series all the way back to 1975 (although the official start of sale date is not confirmed). The charts do not answer every question, but they shed a huge light on the series. All 13 charts are posted both in a collated PDF and as a zip file of all the separate high-quality TIFF images.

Tuesday, 28th May

Following the unexpected discovery of an older schema of Micro Switch SD Series switches, it seemed worth giving Honeywell another try to see if they could locate any details on their old switches.

Details are scarce with the series having been discontinued nearly 20 years ago, but they were able to turn up a couple of drawings, one each for SW and SN Series, which has helped clarify a number of historical details. Most interestingly it shows that SW and SN appear to have been companion series from at least the period of 1995 to 1999, rather than SN having replaced SW. With luck, they may able to recover more documenation.

Monday, 27th May

I thought I read somewhere that Micro Switch SD Series was DIN-compliant, as highly unlikely as that seems. That would point to an introduction date of around 1982. Very little practical data gathering has taken place with SD Series, so off-hand it was hard to be sure. However, it is now clear that SD Series was in production as far back as 1976, as demonstrated by model 125SD12-1.

This keyboard uses an older part number schema, with one fewer position in the identification number, and seemingly at least one position with a different interpretation to the 1001SD Series schema found from 1998. One possibility is that the old switches were 1SD Series, and that 1001SD was chosen when revising the schema. This remains pure speculation.

Saturday, 11th May

UncleFan found an eBay listing for the Yamaha QX1 in which a broken Alps KCC switch could be seen. On Geekhack, the QX1 is noted to have “a linear switch found on the NRC f020 Yamaha qx3, and qx1”, which is Hirose MX1A-0NNN. As such, this machine seemed not to be worth further investigation, as the Cherry switch part number could be retrieved from the readily-available QX3 service manual.

However, having now purchased the QX1 service manual from Mauritron (to avoid hassling Yamaha further), I can now see that indeed the QX1 uses switch KCC10903, which is the model number I speculated it would be upon seeing the eBay listing. The switch can be seen more clearly on the Introvert’s Yamaha QX1 Retro Review, and is a standard KCC green momentary switch.

This now means that KCC lower-weight momentary uses old part number KCC10903 and new part number SKCCBK (as previously obtained from Eleport in Japan). This marks the very first Alps data entry switch type where we have both the old and new part number.

Tuesday, 7th May

Based on an unfortunately barely-legible copy of two pages of the May 1985 Fujitsu magazine (which cannot be posted online), the Fujitsu reed switches page is updated with more details on each of FES-5, FES-8, FES-9 and FES-4.


Saturday, 27th April

Tuesday, 23rd April

With the forthcoming 1993 Alps catalogue scan due from lsoelxi, I figured that I should ask Sandy to confirm whether the 1994 Alps catalogue really did give the series names of “CM” and “CL”, as this would revert a change to “SKCL” and “SKCM” by the time of the 1994 catalogue.

Sandy confirmed that “CM” and “CL” were his own abbreviations, and that the 1994 catalogue does name the series as “SKCL” and “SKCM” as expected.

This clears up one nasty point of confusion over the naming. Now we only have to figure out “CM(KCM)”, “CH”/“SCH”/“SCK”, and the new problem that the “KF” prefix—denoting “full keyboard”—was used for both keyboards and switches in the full-travel membrane line! This may become clearer when the whole 1993 catalogue is ready. Sadly the catalogue is not old enough to cover SKFN/SKFM series.

Sunday, 21st April

Added some brief details on Tipro and Tipro keyboards. Currently details on the older keyboards are scarce.

Saturday, 20th April

Added some notes on NMB desktop membrane keyboards as well as the Model NOTE85A notebook keyboard.

Wednesday, 10th April

Kiyoto has located a set of Japanese patents relating to Fujitsu leaf spring. I have tentatively reclassified the various leaf spring types according to the suggested chronology from these patents, but there is still a long way to go.

Monday, 8th April

My TESLA Hall effect switch and some TESLA keycaps arrived from 10ko in Bulgaria today. I have no idea what happened to the switch (the plunger has been sliced narrow and now it is quite wobbly) but the keycaps are intact, and these and the switch permit keycap mount comparison between Micro Switch, TESLA and Omron. These three brands have very similar keycap mounts that are almost but not quite compatible, for different reasons.

These types are now detailed under the new keycap mounts section. Unlike the existing keycap compatibility page, this section places each group of similar mounts on a separate page for simplicity and to permit more details to be recorded.

This section (like any other) will be expanded upon over time.

Saturday, 6th April

Kiyoto is on a roll. He has located a large number of Fujitsu datasheets on their site, including the datasheets for Fujitsu FES-360 Series, which is first-generation leaf spring. FES-360 Series is still in production, but only for existing customers. It seems to be a fairly small series, offering 59 cN momentary action only, although the oldest PDF for it is from 2001, so it may be that other models were long since discontinued.

Thursday, 4th April

Kiyoto (聖人) sent me a link to the datasheet (or catalogue entry) for Fujitsu FKB2500 Series. Although it does not offer any clear insight into Fujitsu’s naming and classification system, it does match the suggested naming arrangement listed under Fujitsu keyboard series. It also offers the first specifications on a Fujitsu mechanical switch type.

Monday, 1st April

Posted a list of keyboard types discovered to date in Roland and Yamaha service manuals, along with Yamaha non-keyboard types. The Roland non-keyboard types will be added later when time permits. This page represents some of the raw data already presented under Alps series names and model numbers.

Also included is the first confirmed instance of an Hirose Cherry M83S, specifically the standard part M83S-0N00 as found in the Yamaha QX21 (1.5 mm travel version).


Sunday, 31st March

As noted under wiki errors, US patent 4529849 is incorrectly cited as being the patent for second- and third-generation leaf spring. In fact, it is the patent for the membrane leaf spring types. Membrane leaf spring has been mentioned at least once—as “4th gen Fujitsu leaf spring”—but not depicted.

Kiyoto in Japan has demonstrated that the Fujitsu FMR-30BX has a moulded Fujitsu membrane leaf spring keyboard, as documented in the patent. It is possible that the integrated-membrane type shown in the patent was changed to use a modified form of the existing contact assembly from the original leaf spring switches.

Thursday, 28th March

Sunday, 24th March

The Fujitsu date codes and Fujitsu keyboard series pages are both updated with additional examples. In the latter case, this includes 3100 and 3700 (ultra-flat leaf spring keyboards), 8000 and 8200 (tall reed), 9200 (reed that might be shorter) and 2300 (third-generation leaf spring). 2700 is removed for now, as it referred to a single photo that did not show the switches.

Thursday, 21st March

Having received two SN Series switches from STRONIC in France (101SN11 and 201SN1B1, with the latter in its original packet), it has become clear that these are identical to SW series, except for having a base to hold them together for PCB mounting.

Wednesday, 20th March

Since the SMK series and part numbers page does not offer any illustrations, a separate SMK series page is now posted with illustrations of the known series, mostly taken from SMK’s catalogue pages. In particular this includes KBS03 Series, the membrane-based alternative to the better known KBG family (which looks similar but uses conductive domes over a PCB).

Sunday, 17th March

Finally written up and illustrated the dual-magnet tactile and click mechanism of the Omron B2H-F7W Hall effect switches that I obtained in September last year.

Sunday, 10th March

Re-inspection of the Hirose M83S, M83A, MD and MJ series datasheet shows that the force figures are not indicating the permissible manufacturing range, but in fact the tolerance (as recently determined for US M4/M5/M6). The Cherry common schema page along with the MD and MJ schema pages are updated accordingly. The range for MD, 50〜80 gf, comes out at 65±15 gf, and 65 g is what the Epson PX-8 Technical Manual gives for its standard weight MD switches.

Saturday, 9th March

MEI T-5 subseries T-5D has since been confirmed to exist, and is presently on order from Datalux. Once these arrive (Brexit willing) it will be possible to see what they are.

Friday, 8th March

Wednesday, 6th March

Tuesday, 5th March

Sunday, 3rd March

Saturday, 2nd March

Added newly-discovered T-5V subseries to the MEI T-5 page.

Friday, 1st March


Thursday, 28th February

Tuesday, 26th February

Sunday, 24th February

Friday, 22nd February

Tuesday, 19th February

Saturday, 16th February

Wednesday, 13th February

Tuesday, 12th February

Sunday, 10th February

Saturday, 9th February

Sunday, 3rd February


Wednesday, 30th January

Tuesday, 29th January

Sunday, 27th January

Friday, 25th January

Sunday, 20th January

Monday, 14th January

Saturday, 12th January

Wednesday, 9th January

Sunday, 6th January

Wednesday, 2nd January


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