Jump to page content


Factual updates and other interesting changes are reported here. Adjustments and tweaks are not listed.

Follow the updates RSS feed: View RSS feed

Updates for 2020


Thursday, 31st December

After almost exactly two years, the Cherry M5, M6 and M73/M74 design page has finally been updated, to reflect current knowledge and correct errors in the text, the HTML and the illustrations. There is now a diagram showing the different plunger forms, including the SPDT plunger form thanks to UncleFan who supplied me with such a switch.

Photos provided by Camacazzi in Australia reveal that RS 338-765 (in his or her case, Style A M61-0120) has the exact same defacing of the Cherry branding as the Style B′ switches that I obtained from facetsesame at Deskthority in 2014. Clearly then, RS was attempting to hide the identity of the original manufacturer. Since this is the only Cherry type they knew about, mine are likely to also be M61-0120, although the factory remains a mystery. (RS have 338-765 listed as M73-0120, but they were sourcing their parts from the US previously, judging by the example discovered.)

Add comment

Friday, 25th December

There are currently two candidates for the world’s first “intelligent keyboard”. This term was used by both Micro Switch for their 103SD24-1, advertised in October 1977, and IMSAI for their IKB-1. An “intelligent keyboard” referred to a keyboard that used a “microprocessor” (specifically, a microcontroller) as its encoder implementation instead of a plain encoder circuit (in TTL or LSI). The date of introduction for the IKB-1 is not clear, but the circuit diagrams date back to June 1977, making it contemporary with Micro Switch’s offering. The IKB-1 even implemented dynamic key swapping, although with no non-volatile storage, the remaps would be forgotten when the keyboard lost power.

Add comment

Tuesday, 22nd December

A new keyboard encoder ICs page contains a brief list of a few known LSI encoder ICs (pre-microcontroller encoding) along with links to the pages containing the datasheets for them; this list was previously on the encoding and output page. That page now has brief notes on both LSI-based encoder ICs and microcontroller-based encoders.

Add comment

Friday, 11th December

Having talked with Günter Murmann further, I am now satisfied that the custom type produced by Cherry for HP as a substitute for Datanetics DC-60, is Cherry M11, not M1. M11 is what we initially opted for when Cherry supplied the drawing for it, but M1 was the correct interpretation of the part number. It now seems that, while Cherry M9 was followed by MX (to retain a single-letter series code), M11 (and possibly the unconfirmed M10) used non-standard series names.

Add comment


Sunday, 15th November

As time passed, it became clear that it would be helpful to classify the different tactile approaches used. Comparing the general approaches used with known switch types may help identify optimal force curves and guide the design of tactile mechanisms to accomplish them. A new tactile feedback page attempts to classify tactile feel, based on Jacob Alexander’s and SPARC’s force curves.

Add comment

Thursday, 12th November

Yesterday, I received a package of 102 switches from olepigeon in the United States, all NOS surplus parts, largely if not entirely from Excess Solutions. All but one type is unlisted on their store. Included in this was the recently-discovered Marquardt Series 6184 tactile type. I came across this two months ago in Electronic Engineers Master 1989–1990, and never expected to lay my hands on them. Now, thanks to olepigeon, they can now be observed. They use a click–tactile mechanism unlike any other. Note that although the EEM catalogue entry listed them as “tactile”, these are click–tactile switches. At least, it seems to be the most likely explanation that these are the same switches, although it is possible that this is a separate click type that was introduced later, or introduced but never advertised.

Add comment

Thursday, 5th November

A new page is posted on Data Interfaces, Inc. and their known keyboards, keypads and switches. They produced low-profile switches with dual pairs of gold-alloy crosspoint contacts connected in parallel, in a similar manner to Omron B3K. The switch contacts were separately enclosed for protection against foreign particles, just as some modern switches. No photos exist of either the keyboards or the switches, but the descriptions are clear enough that they may be sufficient to identify an unknown switch should one be found from the 1970s that matches.

Add comment

Monday, 2nd November

Further magazine exploration has turned up a variety of model details of Raytheon’s reed switches. We now know that these are divided into two types: KBSR with a sloped base and KBFR with a flat base. This in turn led to an advertisement in a Dutch magazine containing more complete specifications, along with an explanation of the two types. The details are added to the new KBSR and KBFR page. The mechanical switch details are now moved to a KBSM page.

Add comment


Tuesday, 27th October

A magazine article for Cherry’s then-new “gold-crosspoint series” of switches has turned up in a 1968 issue of Electronics magazine, scanned by Bitsavers. This article confirms that S31 Series was used in Hewlett-Packard’s 9100A programmable scientific calculator. By naming HP as a Cherry customer, this leads some weight to the suggestion that all of the “mousetrap” switches in HP equipment were supplied by Cherry. See the new Cherry Series S31 page for details.

Add comment

Sunday, 18th October

An eBay listing for a Texas Instruments Silent 700 ASR/KSR keyboard has drawn attention to the overlooked fact that Clare-Pendar Series S840 surprisingly dates back at least as far as 1973. (Snuci had already noted that his Bendix control panel is from 1974.)

Discussions with Peter Cherry (former Cherry president) and Günter Murmann (former vice-president of engineering at Cherry in Germany) have recently led to a number of clarifications of Cherry product history:

Additionally, a US FTSC type existed, the Next Generation Keyboard, offering both linear and tactile feel options. This was a different design from the German system, that seems to have had more in common with the DIN-compliant solid state capacitive keyboards.

Add comment


Monday, 28th September

Another advertisement, another Stackpole switch type. This time it is KS-200, advertised in 1981. The photo in this advertisement is even harder to make out, but chances are KS-200 is their standard switch array, referred to until now as “Stackpole switch grid”. Specifically, KS-200 is likely to be the pre-DIN grid, as “Stackpole switch grid” covers both the pre-DIN and DIN types (the latter being KS-200E). KS-200 also includes the smaller modules including single switches, as depicted in the advertisement. Having gone through all of Bitsavers’ scans of Computer Design from January 1967 to June 1981 (and various later issues), there has been no sign of a KS-100, and no official advertisement of the Lo-Pro switches. Hopefully further advertisements will show up in the other magazines that they have scanned, or some other details to indicate whether there was an earlier array type, that corresponds with the HP keyboard with a Stackpole array that more closely resembles Hi-Tek’s original design.

Additionally, the second Mechanical Enterprises Sabrecoil example has shown up: Sabrecoil was selected by AMD for their AmZ8000 CPU evaluation system. This can be seen in a couple of advertisements, added to the Sabrecoil page.

Add comment

Sunday, 27th September

An interesting conversation with Peter Cherry (Cherry founder Walter L Cherry’s son, and former Cherry president) has cleared up much of the mystery surrounding UB80-01AA. It seemed logical to assume that these keyboards were made by Cherry using switches provided by Hi-Tek, on the basis that Hi-Tek originally did not produce complete keyboards. However, these are instead Cherry-produced Hi-Tek keyboards, produced at the behest of DEC. The reasons behind this are no longer known.

Add comment

Saturday, 26th September

A newly-discovered advertisement indicates that SMK made reed switches in the same form factor as J-M0404 mechanical switches, as well as “sealed membrane type units”. All these types fell under JM-0400 series, which will also contain the J-M0409 subseries not yet observed. See the SMK series page for details and the advertisement.

Add comment

Friday, 25th September

There is now tentative evidence that Maxi-Switch 6000 series is “vintage linear”. Advertisements and documentation for 6000 series are not clear yet. The scarcity of clear details and examples makes it impossible to be certain, but the part numbers for the “vintage linear” keyboards do suggest Series 6000 (while the PCB codes suggest Series 6300). A keyboard with “vintage linear” switches appears to tie up with a product leaflet indicating that this keyboard (Maxi-Switch 2160029) is a MAX-II (or MAX-11, which seems to be a printing blunder), a 6000 series keyboard.

Add comment

Saturday, 19th September

A Cherry advertisement placed in Computer Design in September 1983 offers some unexpected features of the then-new MX series: double contact, double pole and angled plungers. Angled plungers are perfectly possible, but have never been observed. The patent depicts double pole, but this has also never been seen. Double contact is not defined precisely, and nothing matching this description has been seen either; the split movable contact design shown in the patent might be there to allow each side to flex separately, with its own contact prism.

Günter Murmann, the designer of the MX switch, implied that these options were produced, but fell out of favour over time. It is not clear what part numbers they would have had.

Add comment

Friday, 18th September

Having only just found the KS-200E and KS-500E advertisement yesterday, another Stackpole advertisement has turned up, this time for KS-600E. KS-600E keyboards use discrete plate-mounted switches, that were also offered for sale separately. This may be the keyboard type of the Zentec Zephyr DD/ID220 that Redmaus found; the magazine illustration is not clear enough to determine this for certain.

Add comment

Thursday, 17th September

Stackpole advertised KS-200E and KS-500E keyboards in Computer Design in early 1984. The advertisement, like various others, is confusing as to whether KS-200E and KS-500E are keyboard models (with a pre-defined layout) or simply switch types. KS-200E is the mechanical type, depicted as the “interlocking” or “puzzle piece” discrete PCB-mount switch, but described as being either discrete or an array; it would seem that all the DIN-compliant mechanical switches were classified as KS-200E (possibly with “E” denoting ergonomic). KS-500E is their membrane type. The advertisment is now added to the Stackpole page.

Add comment

Wednesday, 16th September

Continued examination of back issues of Computer Design magazine at Bitsavers has now yielded additional models of Raytheon keyboard switch. The reed type of KBSR-1 is now confirmed, and this was complemented by a “double-level” KBSR-2 type. The mechanical equivalent was KBSM-1, and although a “double-level” mechanical type was offered, its model number was not given.

Searching for “KBSM-1” netted an eBay listing with clear photos of this type, which is very similar to the sample collected by Meryl Miller. Notwithstanding my opinion of eBay and long-standing vow to never use their services, some lucky individual was able to acquire this immense rarity for the lowly sum of US$2.95 last month. For a new-old-stock switch designed around 1967, that was a lucky purchase by one “1***e”; his or her bid was the only one, for which they can thank how poorly-known these switches are, this being the first and only confirmed sighting of KBSM-1 (Meryl’s example is probably the same model but the specifics are lost to time).

Add comment

Sunday, 13th September

Looking through the Electronic Engineers Master catalogues has also turned up two more (identical) MEI T-5 Series advertisements. This finally gives us T-5P as the stemless type, and a confusing depiction of T-5H.

The SC, KD, SD and CT advertisement is now uploaded to the Micro Switch SC, CT and ST Series page.

A Cherry advertisement in Electronic Engineers Master 1988–1989 mentions only German products under the keyboards section (G80, MX, M8 and M7), suggesting that US keyboard and switch production had ended by 1988. In particular, this means that M7 would have supplanted M5/M6 by this time. (The advertisement is linked from the M7 page.)

Add comment

Saturday, 12th September

Back in January 2019, Bitsavers scanned in some more Electronic Engineers Master catalogues; with no way to subscribe, nearly two years have passed since!

The 1988–1989 and 1989–1990 catalogues contain some interesting and useful advertisments, including a seven-page advertisment from Marquardt that gives an extensive list of part numbers from Series 6184. From this, we learn that alternate action and tactile variants existed, as well as optional internal diodes. A choice of travel of 4 mm and 2.5 mm existed for the momentary types, which was already evident from the datasheets that Marquardt provided me in 2016, that I overlooked at the time.

To make extracting advertisements easier, I have also written myself a small program that wraps Ghostscript, that extracts the pages and sets the author and title in a single step.

Add comment

Wednesday, 9th September

Two updates today:

Add comment

Tuesday, 8th September

Using advertisements provided by Marcin Wichary as a starting point, the Licon and Cortron page is now updated. We now know that the most common ferrite core switch is Series 555, which appears to cover both “Early Ⅱ” and “Early Ⅲ” styles. In addition to Series FC2500, there was also a FC-2550 that seemed to be produced first, with no clear indication on how the two series differed. FC-2550 is described as having “true linear feel”, while all known DIN-compliant ferrite core keyboards from Cortron are tactile. There is also a magazine advertisement from 1978 for “Series III” switches, with no way to determine what these are, other than that they do not seem to match anything that was introduced around that time.

There is now a suggestion that Series 555 part numbers took the form 55-5xxxxx, so the mystery model on eBay (for which I forgot to archive the listing photos) with part number 55-100007, was either Series 550 (seemingly unlikely as that did not use a PCB) or an intermediate type in between the original Series 550 and the later Series 555.

There is still a long way to go, but gradually more details are fitting into place. The mechanical types remain to be discovered, either in a keyboard, or in any product literature. Thus, their identity remains a mystery.

Add comment


Saturday, 29th August

With the first keyboard to use Elec-Trol reed switches having shown up, I have posted a brief page listing all the known Elec-Trol reed switch types. With Elec-Trol having been bought by Hamlin, and Hamlin in turn acquired by Littelfuse, the odds of finding any details from the manufacturer now seems impossible. Elec-Trol seem to have largely vanished into oblivion, with no mention of them in any existing archive material.

Add comment

Monday, 24th August

While searching for any remaining details on Oak Series 400 switches, I found instead the Manual Input Devices section of Computer Design from December 1965, because it mentions Oak rocker digit selector switches, and Digitran’s Series 400 thumbwheels.

The article itself was a fortunate discovery, as it covers a number of very early keyboard types from the 1960s. This included two models (PK-144 and PK-164) from Invac, who claimed to have invented the photoelectric (optical beam) keyboard, for which they filed a patent as early as the end of 1960. From here, I was able to find brochures for both PK-144/PK-164 and the later Series PK-200, now all described on the new Invac page.

Photoelectric encoding is now also mentioned on the encoding and output page.

Add comment

Sunday, 16th August

The Oak Series 400 page is finally overhauled and cleaned up. There is still not much more information, but what information does exist is now gathered together and presented much more clearly.

Add comment

Thursday, 6th August

As time passes, there is a growing number of switch types yet to be seen, or yet to be discovered in a keyboard. These include switches known only from patents where no photograph is available, or switches whose only known photograph is in the form of promotional literature. Some of these are now collected together on the unseen switches page.

Add comment


Sunday, 12th July

Having recently split the remaining Fujitsu reed information into separate FES-5, FES-8, FES-9 and FES-4 pages (with FES-1/2/3 having been split out previously), I have now expanded the details of FES-8 according to what little of the Fujitsu journal article I am able to read and understand. For example, it seems that Fujitsu offered both レベル出力 (level output) and パルス出力 (pulse output) Hall effect options. The are no photographs and measurements of any Fujitsu reed switches yet, as it may be some years before I lay my hands on any of these types. What is disappointing is that no-one with an illuminated FES-8 or FES-9 switch has ever checked what part number is written on them. It may be a long time yet before anyone encounters the Hall effect types, however.

On the subject of Hall effect, the encoding and output page recently gained a section on Micro Switch’s two-of-N code direct encoding, using binary encoders to convert the two-of-N codes directly to ASCII codes without the need for a microcontroller.

Add comment


Wednesday, 24th June

Having now received my order from Incotel (as mentioned in the previous update) I have now been able to examine the M76-0899 switches. These have six terminals, and I determined that two of them were functionless, until I opened one up and realised that the first switch I tested was defective. They are in fact double pole double throw (DPDT) alternate action, with each side having the opposite operation (the output terminals are NO+NC on one side, and NC+NO on the other). The mystery of M75–M78 is finally revealed: where needed, these switches have side-by-side pairs of movable contacts, with the stationary contact also split into two. The triple and quadruple pole switches work this way, as do the double-pole alternate action switches which reserve one side for the latching wheel.

In addition to being round mount, these have silver prisms for higher electrical capacity, the first time this has been observed in M7. M76-0899 is a very interesting model, that is most likely a customer-specific part.

Add comment

Monday, 15th June

UncleFan found a store in Lebanon—Incotel Electronics—selling a couple of Cherry types: M73-0800 and M91A-11NN. On further inspection I also turned up M76-0899 and some RAFI and Siemens models. The nature of M76-0899 can’t be confirmed until it arrives, but based on the data for M76-0890 (a catalogue part in 1982), it should be a 1A+1B alternate action switch.

M91 however was an interesting find, because until now I believed that M91 did not exist. In fact, the part number chart for Cherry M9 has a gap where M91 could be listed. The way that the lines are drawn suggests that the M91 entry was not removed, and some of the boxes of M91 switches at Incotel were made in 1986, after the chart was last revised. This would suggest that M91 was considered, and nobody ever filled that box in after it was made available.

Incotel seem to have a good supply of M91A-11NN (with clear stems) in 800-piece boxes dating to 1985 and 1986, as well as an unspecified black stem version that may be M91A-41NN (as per the switches in the Ultratech Miniprint).

Add comment


Monday, 18th May

The Hall effect keyboards is now updated to reflect a couple of discoveries about how Hall effect keyboards are designed, as well as additional details not previously covered.

As someone who does not understand much about electronics, and someone who does not have a large stockpile of keyboards to examine, these discoveries are interesting in that they make sense, but they are also presently impossible for me to prove. It’s a strange experience documenting a subject that you don’t understand, but hopefully the result is that more people will have a much better idea about Hall effect keyboards than they did before, a subject that remains very poorly covered.

Similarly, the encoding and output page has seen numerous updates recently.

Add comment

Sunday, 3rd May

There is a particular keycap family that has for years resisted identification. This family was used on most BBC Microcomputer keyboards (those made by Wong’s and PED, but not those from the SMK-made keyboards). An almost identical type can also be found on at least one SAGEM keyboard, seemingly from a TX-20. I concluded some years ago that the BBC Micro keycaps always seemed to be Comptec, but Signature Plastics never recognised them. Nonetheless, they have distinctly Comptec characteristics, that do not fit with any other manufacturer’s product range. This includes the internal step that is present in each of SA, DSA and DCS.

Recently I have dug into this again. As Acorn has closed down, all of their records are gone. Chris Turner, Acorn’s chief engineer at the time, reports that the BBC Micro keyboards arrived from the manufacturers fully-assembled, and it seems that Acorn did not choose the keycap manufacturer. I had already encountered an excerpt from a DRAM Electronics Ltd catalogue—listing BBC Micro spares—where one of the keycap manufacturers was given as “Comtec”, which I took to be Comptec spelt incorrectly somewhere (perhaps even by Acorn themselves). DSA family is structurally very similar, with the same thin walls and the same low internal step, and as a DIN-compliant family it likely goes back to the early-to-mid 1980s. This means that the reduced-plastic design seen with modern Signature Plastic keycaps could be as old as the 1980s. The BBC Micro keycaps tend to have writing on the inside where Comptec placed it, although unlike DSA and some old DCS, it seems to simply give the mould cavity numbers or some other internal code. (Comptec had more than one factory and more than one mould design per family, so these characteristics vary.)

For the mystery keycaps, we can rule out SA, as they are clearly not SA family: SA uses much thicker plastic and a much larger internal step. They are also not any of Comptec’s DIN-compliant families (DSS, DSA and DCS) due to their height. The Comptec-like BBC Micro keycaps are all stepped profile, and I remembered that there was one more family that has long since disappeared: SS. Since SS was sculptured, a row from this could be used to make a stepped profile. Thus, these mystery keycaps are likely to be Comptec SS family.

A keycap profile demonstration props topic at Deskthority from 2015 contains an unattributed chart of DSS, SA and SS. The middle row profile from SS is precisely the same shape as the BBC Micro keycaps. That row is 0.410″ tall. Signature Plastics did not state precisely where on the keycap that height is measured, but assuming it’s the centre over the base, the BBC Micro keycaps are 0.419″ tall at that point, which is very close. This chart seems to verify that the Wong’s and PED keycaps on the BBC Micro were Comptec SS family.

The SAGEM keycaps are flat (“all rows”) profile and the same height as shown for SA on the same chart, which suggests that SS also had a flat profile option, similar to SA but made using the revised reduced-plastic moulding.

Having suggested this theory to both Signature Plastics and a former Comptec employee with whom I was corresponding, neither have responded, but at this point it seems likely.

(While gathering more data on these keycaps I also talked to Professor Steve Furber about the implementation of the BBC Micro computer keyboard, which I have since documented in more detail on the encoding and output page.)

Add comment


Sunday, 19th April

A new page is up on Hall effect keyboards. It is comparatively brief, but it provides what could be considered a few interesting details.

There is also now a page that collects together the details on TESLA Hall_ICs. They offered two types: full-height (used with switches based on Micro Switch SW) and low-profile (used with switches based on Micro Switch SD). Each size came in a level type and a pulse type, for a total of four models. Unfortunately it seems that TESLA declined to write anything about them, so the behaviour has to be determined from the specifications and circuit diagrams.

While looking for photos of the SD clone switches with TESLA switches, something else interesting turned up. Buried deep in the Redmaus Megasale topic is a Zentec Zephyr DD/ID220 keyboard with switches that appear to be a plate-mount version of Stackpole’s grid switches. While Stackpole interlocking was discrete but still PCB mount, these seem to be discrete plate-mount units. This is a new discovery that went unnoticed last year.

Add comment

Thursday, 16th April

In August last year I bought some Micro Switch 1PB871 switches. I included a 1PB2001 in the order purely for the sake of illustrating the Micro Switch PB page. 1PB2001 is a combination of an SM basic switch (“microswitch”) and a 2ED “untimed pulse contact buffer circuit”. The latter is a special circuit that provides debouncing, so that the switch unit can drive logic circuits directly. I never paid it that much attention until I started looking into sensing and encoding in more detail. The 1966 Bulletin ED contains the circuit diagram and, after some pondering, I can see what they did. (Those who are more electronics-inclined would find it obvious.) Micro Switch took advantage of the presence of both normally-open (NO) and normally closed (NC) terminals on a basic switch, to drive a flip-flop. Operating the switch activates the flip-flop, which remains active until the switch is released, and the normally-closed current clears it. This way, the bounce period is ignored as the flip-flop remains active throughout. This principle can be extended to any switch series with NO-NC as a supported configuration, including Cherry keyboard switches from the 70s.

Additionally, I found a brief PDF on datasheetarchive.com that finally confirms that Fujitsu FES-8 and FES-9 effectively differ only in profile. Aside from a brief overview of the family characteristics and some hard-to-see photographs, that is all the detail provided.

Add comment

Monday, 13th April

Having finally read through the relevant patent, I now understand how the Mechanical Enterprises Mercutronic coding switch works. (This is the full version of the simpler non-coding mercury type mentioned at Deskthority as an unidentified product.) A detailed diagram of such a switch was posted to Twitter last year by Tube Time, taken from the December 1969 issue of Electronic Engineer magazine (volume 28, no. 12) With luck, it will be possible to get the whole article scanned in by the Linda Hall Library later this year (as and when the staff are able to return to work on premise). When drawing an example diagram of two coding switches I realised that there was a major problem with the design, and that diagram cleared up a point of confusion in the patent about how Mechanical Enterprises addressed it.

Have you ever looked at late 60s and early 70s keyboards and wondered what their large arrangements of diodes are for? These diode matrices are now covered in the first part of the new encoding and output article along with information on self-encoding switches, which made a brief appearance in the late 1960s before disappearing. Only late 60s and early 70s encoding is covered at the moment, which is the important part that I have been keen to document for some time. It would be nice to also document Datanetics’ encoding system, but Meryl Miller appears not to remember how it worked, and it does not appear to have been patented (I only learnt of it from his personal notes). That approach, too, seemed to soon vanish.

To support the above article, there is now a page on Micro Switch KB encoding switches. Additional photographs are due at some point in the future.

Add comment


Friday, 27th March

Although a few Raytheon keyboards are known, it appears that there is only one discovered example made by Raytheon themselves, using reed switches (the others were made by Cortron). Meryl Miller collected a sample switch at the end of the 70s or early 1980s that appears to be Raytheon — I could have had it and would have had it if I had realised it was a keyboard switch (likewise his Fujitsu FES-2 and Micro Switch 1PB870 and KB types).

A new Raytheon page collects together what little is known about Raytheon’s keyboards and switches, including a single photo of Meryl’s type and a diagram showing how it appears to work, based on his photograph and a patent for an older design.

Add comment

Thursday, 12th March

At the end of the 1960s and the start of the 1970s, manufacturers were finding a surprising number of ways to design switches that could directly address logic circuitry without contact bounce. The earliest known dedicated bounce-free keyboard switch type was Micro Switch SW using Hall effect, introduced at the end of 1968. Licon put out Series 550 ferrite core (“magnetic valve”), that goes back at least as far as the end of 1970. Perhaps the strangest was Mechanical Enterprises Mercutronic, a family of designs that used mercury-containing tubes for switch contacts, available for keyboard applications from around 1970.

RAFI used Hall effect from around 1973, in the form of RC 72 series. This was not their original contactless switch: an older design is known from patents, using magnetoresistance, that has yet to be encountered. Fortunately RAFI still have a 1972 catalogue documenting these switches. RAFI magnetoresistive switches appear to have no series name, only part numbers; they are described simply as “contactless”.

These may well not be RAFI’s oldest keyboard switches, but this is the oldest catalogue that RAFI were able to find, and both this and the RC 72 catalogue defied the odds against being recovered.

Add comment

Wednesday, 11th March

RAFI have now scanned in for me the complete RAFI-System 72 (RC 72) catalogue. The catalogue was printed in 1983, which explains why the Hall sensor characteristics relate to later Siemens models (models seemingly not in existence when the switch series was introduced). The catalogue includes a diagram of the internal structure of both the Hall and mechanical types, and from this it is clear that this is indeed the annular-magnet type from the patent filed in 1972, which ties in with RAFI’s unclear indication that these switches were introduced in 1973. Jacob Alexander’s example will thus be a redesigned version. Two more switch types can now be seen: RC 72 N mains power switches, and keylock switches.

All we need now is details of RAFI’s original switches, which appear to have been magnetoresistive.

Add comment

Friday, 6th March

Fujitsu FES-1/FES-2/FES-3 now has a page of its own, on which the original specifications and part number format is now documented, as per the Fujitsu magazine scans previously provided by Kiyoto. Curiously these are in a totally different format to the numbers found stamped on FES-1, FES-8 and FES-9 reed switches.

Add comment


Tuesday, 25th February

Research has already shown that Micro Switch SW began life with an older plunger design moulded from grey plastic. These older switches can be seen in advertisements, but they have not been otherwise encountered. All discovered SW Series switches had model numbers from 1SW11 upwards; however, model number 1SW1-R can be found on various part listing sites, albeit without any photographs or other evidence. It stood to reason that 1SW11 upwards was the circa 1970 redesign (with black plungers) and 1SW1 upwards was the original 1968 design (with grey plungers).

Finally, visual proof of early 1SW1 has arrived, in the form of a “3D model” of an unidentifiable SW Series keyboard, manufactured around 1969 judging by the dates on the switches. The switches are (surprisingly, for a keyboard that old) marked with their part numbers, with all visible markings being of model 1SW1 from week 26 of 1969. This is the oldest SW Series keyboard found to date. The model label is present but the stamped inscription is either absent or missing from the model; the only visible identifying code is that of the PCB, catalogue listing SW-10033.

This is not proof that 1SW1 was the older-style switch; photos of the next-oldest known keyboard do not appear to show whether those switches were stamped or not, and thus we cannot determine yet whether this is when the part numbers changed. The part number change could have instead corresponded to a change of some other characteristic, such as a redesign of the Hall sensor. As always, more evidence is still required.

Add comment

Monday, 10th February

In October 2019, Deepak Kandepet introduced me to an unknown reed switch type, depicted as switch 2 in a gallery of then-unidentified switches. This type is always marked “ПКМ 1Б” (“PKM 1B”). Some investigation found that some were also marked with a logo that somewhat resembled a smiling face. Later, I came across the Russian Virtual Computer Museum. Armed with a freshly-redrawn logo derived from its brief appearance in Chyros’s TC7063.02.A003.01 Soviet keyboard review (the logo shown in the video is depicted more precisely than on the bottoms of the switches), the museum staff were able to track down the logo to Ukrainian firm Magnit (Електромеханічний завод «Магніт») in Kaniv. Formerly part of the USSR Ministry of Radio Industry, they are now a separate business.

It is possible that they may still remember these switchces, but at present they cannot be reached as their mailbox is full!

There are still many more unidentifiable Soviet switch types, but now one of them is at least partially understood.

Add comment

Sunday, 2nd February

The history of German Hall ICs is now both clearer, and less clear, after Wolfgang Zucker provided some catalogue entries for Siemens Hall ICs from 1977–1985. This in turn made it possible to locate the origin of the PDF previously used as a reference. It seems that some models were quite short-lived, being in production only during the early 1980s. This might be a clue as to why, as early as 1986, RAFI were using HFO Hall ICs. We now also have more details on SAS 201–221, albeit not the supply voltage ranges that could be tied up to RAFI’s RC 72 specifications.

Sadly, still no word from anyone at RAFI at all.

Add comment


Tuesday, 28th January

In 2016, OleVoip at Deskthority posted a photograph of a lone RAFI RS 76 C switch. The Hall IC is marked only with an orange stripe (which he claimed “marks the border between the rest position and the activated position”) and the plunger is uncharacteristically natural plastic colour.

The catalogue pages for Siemens Hall ICs indicate that SAS 251 S5 is marked solely with “orange”, suggesting that this switch has a Siemens IC, and thus that the reason for the different plunger colour is that it offers dual open collector outputs instead of single open collector with enable input. There are certainly sufficient RS 76 C part numbers unaccounted for (obsolete before 2001 and removed from the catalogue) to allow for this, and we know that RC 72 offered a variety of Hall sensors.

From discussion of HFO and Siemens Hall ICs over at the Robotrontechnik-Forum, it seems certain that this is a Siemens IC, based on the plastic texture, terminal plating (silver plated instead of tinned) and housing shape (the latter remaining unexplained). However, it is always good to be as certain as possible. Wolfram Zucker in Germany has a collection of Siemens Hall ICs for sale and he has most kindly added photos of them to his analog ICs page. Most are marked in full or entirely blank (the latter indicating defective examples), but some SAS 261 chips are indeed marked with nothing but a blue stripe, and blue is the colour associated with that model.

Siemens practices remain a mystery (so far, they have declined to respond to questions) but at least it now appears certain that OleVoip’s single loose RS 76 C switch has a SAS 251 S5 Hall sensor from Siemens.

Add comment

Thursday, 16th January

With the help of Holm Tiffe and the Robotrontechnik-Forum, we have made some progress understanding the Hall IC scene of the past. It seemed unlikely that VEB HFO B 461 G was around at the introduction of RAFI RS 74 C, and this was compounded by RAFI RC 72 C offering a variety of outputs (including separate level and pulse types) beyond what HFO are known to have produced.

According to the Ältester B461G? (oldest B 461 G) topic at the Robotrontechnik-Forum, B 461 G is known to go back to 1981, which corresponds with the age of TGL 38658, from June 1982. This indicates that RAFI must have been using an older product range, and this is reported to be Siemens Hall ICs. Unsurprisingly, the Siemens data matches up exactly with the RC 72 C data.

Add comment

Wednesday, 15th January

At any one time, I have a considerable amount of both businesses and individuals from which I am still waiting for a response to a question or enquiry, going back days, weeks, months, or in some cases, years. Every so often, I remember or encounter some of them and give them another nudge.

The other day, I nudged RAFI again, in the hope that they might recognise the high-profile Hall effect switches found in Jacob Alexander’s Express-2 keyboard from the mid-80s. This time, I did get a reply: they are RC 72 C and RC 72 L. RC 72 is a series of high-profile Hall effect and mechanical switches. These series numbers seem to correspond with the year of introduction: RS 74 ca. 1975, and RS 76 in 1976. Tentatively these seem to be from 1973, making them slightly older than the reduced-size switches for which RAFI is better known. RC 72 is reported by RAFI to have been discontinued in 1993. Curiously, the part numbers slot in directly behind those of RS 74, which come directly before those of RS 76.

Some basic details are up; more details will come as time permits, including a complete list of part numbers. RAFI provided a single catalogue page; if they can provide further pages from it (including the extra details on RC 72), I will post those collectively, otherwise I will upload the single page available, which is just a parts list with no specifications.

Add comment

Saturday, 4th January

José Soltren (XMIT) of XMIT Keyboards and now Metadot (Das Keyboard) has produced a set of photos of Das Keyboard Gamma Zulu switches (now proven to be part of Omron B3K series), revealing the part number to be B3K-T135M. The final “M” appears to indicate “Metadot” as suspected. The “35” may indicate that these have 3.5 mm travel instead of Logitech’s 3 and 3.2 mm.

This only leaves finding the part number of Creative PRES, the third customer product based on B3K.

Add comment

Wednesday, 1st January

2019 knowledge round-up

2019 has been another fantastic year for keyboard knowledge, so much so that it seems unlikely that 2020 will beat it. Two major successes were Micro Switch and Fujitsu. Micro Switch has seen by far the biggest gains in knowledge, thanks to charts and literature from Honeywell Sensing and Internet of Things, National Museum of American History Library and the Computer History Museum:

Thanks to Kiyoto, the series name of every known Fujitsu discrete switch has been found:

Numerous Mechanical Enterprises types have been discovered (corresponding to unmatched patents), although most are yet to be observed:

Some other discoveries made in 2019:

Additionally, I have now a huge list of Alps patents for anyone who can read Japanese, including several for “fat Alps”.

2019 has brought with it a couple of other changes. The site graphics are now all converted to vector, to be DPI-independent (and this includes MouseFan’s site). With the exception of the switch collection, the thumbnails are all rebuilt in higher resolution (generally 150–175% DPI, as a compromise). Although my photos range from passable to execrable in quality, the increased detail level of the thumbnails does make a real difference even on a screen at only 120 DPI (125%), with the added sharpness clearly evident.

Additionally, the presence of “.php” in URLs is no longer required. The old URLs will continue to function, but they will redirect to the cleaner URLs.

Add comment