Factual updates and other interesting changes are reported here. Adjustments and tweaks are not listed.
Updates for 2021
Monday, 3rd May
One of the most frustrating companies to track down is Pye Electro-Devices, or PED. Various details exist on their keyboard products, but not a single confirmed photograph or example has shown up. This stands in sharp contrast to fellow British manufacturer Alphameric, from which we have discovered numerous examples to date. Like Alphameric, PED is now gone; some Alphameric staff still work for Devlin (who bought out their keyboard business), but are forbidden to speak, while with PED it’s not clear what became of the keyboard line of the business.
Although PED switches were used in some BBC Micro keyboards, the actual manufacturer of those keyboard assemblies is not confirmed. We do know that PED made the console panel for the Monarch 120 digital PABX, which is the first visually confirmed example of capacitance-controlled transistor sensing. The design here is different to that of Control Devices. This Monarch example may be PED’s Series 90, but this is not confirmed.
Those details that are still discoverable are now added to the PED page. The “PED switch” write-up remains on the same page for now, as none of the information available at present offers any suggestion of their identity, only that they appear to have been available for sale separately.
Friday, 23rd April
A Sharp ZX-510 typewriter in Shallot’s collection has now demonstrated that Alps KFF series survived long enough to be split into SKFF and KFFF series. Thus, although I was incorrect to use the name “SKFF” on the Deskthority wiki based on the evidence available at the time (which I have since learnt indicated KFF series, not KFFF), this error has proven irrelevant as the series became SKFF anyway. The question now is, how long will it be before the first switch part number shows up? After all, electronic typewriter service manuals are especially elusive.
Friday, 16th April
My understanding of electronics is not great, to say the least. In the past, I specifically avoided documenting electromagnetic sensing techniques (e.g. capacitive, Hall effect) as I did not understand any of them; consequently I also avoided certain brands, in particular Micro Switch. As time passed, it became clear that all the brands that I was leaving to others to document, either because they seemed beyond my understanding or because they seemed to have a sufficiently loyal fan base to take care of that, have mostly fallen to me to research and document, as the only person willing to do so.
As time passes, I have also ventured into the electronics side of keyboards. This includes capacitive sensing, in part because some very interesting techniques have turned up, as past updates have revealed. In the last few days, I have made some improvements to coverage and clarity of the capacitive sensing page. There are still no clear details on how any matrix scan keyboards actually work; this may be addressed later as and when I encounter or seek out patents that detail the approaches taken.
The illustrations on the IKOR page are also improved, to better show how the sensing technique works and to bring them more in line with the patent. The actual implementation seems to have rapidly deviated from the patented design, but for the purposes of illustration, the page shows the approach as patented. The modifications taken in production keyboards are not explained in the detail found in the patent.
PS Wave if you are following these updates!
Sunday, 11th April
Another day, another largely forgotten vintage keyboard manufacturer. This time, it’s Control Devices, Inc. Control Devices invented possibly the most convoluted capacitive system, one that required (in addition to the variable capacitor) a transistor, a fixed capacitor and two resistors for every key. These small circuits then drove a diode matrix, which was then fed through a sense amplifier to yield adequate signals strength and a synchronisation circuit to wait for all the sense lines to settle before the output code was delivered. The small circuit within each key station provided each key with its own capacitive sensor. One of the inventors, Donald Gove, was the inventor of the IKOR self-encoding capacitive switches mentioned recently.
A couple of people have come across Control Devices keyboards, but nobody was ever forthcoming with details or illustrations. Some instances were described as “foam and foil”, which raises an interesting question of whether they moved on to more “conventional” capacitive keyboards (using a matrix scanner to centralise the capacitive sensing circuitry), or whether they merely simplified (or cheapened) the variable capacitor portion but retained the per-key capacitive sensors.
Saturday, 10th April
After Marylou Bassi-Dolmans got in contact with me regarding Clare and Pendar, I started investigating these brands anew. During my searching, I found a number of pages with details on Pendar’s capacitive keyboards, but did not get around to reading them, instead simply making a mental note of the summarised contents in the search results while I looked for more details on the history of the US Pendar. Having gone back to read up on this interesting new line of research, all those search results had vanished without trace. Even the browser history entries for prior searches found nothing. Sadly I have no recollection of what sites had those details, only that possibly it was all duplicates of the same material. It was a description of how Pendar in France—the buyout company—had set up a line of capacitive keyboards in France, something for which there is unfortunately no patent to examine.
Someone called Furieux Furet posted a photo of a single switch from a Pendar keyboard at Deskthority, and then—as so many people do—vanished without ever completing the investigation. There is not even a single photo showing the complete keyboard, and no attempt to investigate the switch workings. The switch with its external springs had a strong suggestion of being capacitive. Finally, a second keyboard has shown up with this switch, an unknown Goupil keyboard, this time depicted in considerable detail, but (from the photos to date) not identifiable as Pendar. Ricardo Guzzetti did indicate that Goupil was a Pendar customer, so it seems that this keyboard is one of theirs.
Hopefully more details will come to light one day. After sending messages to a number of ex-Pendar staff via a French social media site, not a single one has ever responded. Not one.
Thursday, 8th April
A brief page is now up for Applied Dynamics International. Applied Dynamics is the primary name for the business that also traded as Collimation Keyboards. The well-known Collimation D40.592 photoelectric encoder keyboard can now be seen marketed as the ADI Series 5000 in 1977. The advertisement also gives some brief specifications.
Saturday, 3rd April
When I first encountered the idea of encoding switches—specifically Mechanical Enterprises Mercutronic and Micro Switch KB, it seemed like a pointless and short-lived notion. This was not helped by a misunderstanding of when KB encoding switches were introduced, now suggested to be 1964.
In reality, self-encoding was a fairly common technique, found thus far in conductive, capacitive, photoelectric and inductive forms. What makes them seem uncommon is their rarity: self-encoding keyboards are scarcely encountered, with known examples seemingly limited at this stage to photoelectric keyboards from Invac and Collimation.
Joining these ranks is another manufacturer whose products also remain undiscovered is Synergistics. Synergistics keyboards, obtained from the acquisition of Peripheral Equipment Corporation in 1968, use a semi-reconfigurable conductive implementation. Keys can be rearranged at will (albeit seemingly only by removing all keys to its right in the same row) but changing the encoding requires sourcing a replacement coding mat, the small insulating sheet with break-off tabs that determine which pairs of switch contacts are active. This approach, including seemingly a complete lack of any on-board circuitry besides the output buses (including the absence of an electrical monitor or its accompanying resistors) led to a keyboard deemed at the time to be very cost effective. Indeed, a 1969 selection of products on the market gave a $50 quantity price, the cheapest product listed by a wide margin. Mercutronics came in second place at $75, and all other offerings were priced at $100 or more.
Sunday, 28th March
There are certain keyboard designs that, for the moment, seem specific to a single company. One of these is IKOR’s capacitive encoding system, which may be their only keyboard design. No such keyboard is yet know to have been observed, and it seems that they did not remain the market for many years. IKOR keyboards used a self-encoding technique where each output bit is detected separately via capacitance. An electrostatic shield is fitted to each key, with a hole punched in it for each output bit to be set as a 1. Details are given in the patents, and some rough illustrations are also posted to help explain this rather strange sensing and encoding method.
Saturday, 27th March
It seems that Micro Switch SD Series is a little older than I thought. I have been reviewing the collection of advertisements and articles that Marcin Wichary sent me. I tend to disregard much of it, as the scan quality is generally terrible, and much of is completely unattributed: the only trace of the origin of the advertisements is when the scanned pages bear the publication details, and full-page advertisements in magazines often lack even a page number. With the publication details recorded, I could at least request a fresh scan from the Linda Hall library, as I did with the Maxi-Switch Series 6000 and 8000 advertisement where it was critical to have the illustration in a usable form. I have been forced to delete some of the advertisements as the lack of even the year of publication means that I cannot use them as a historical record; perhaps they are older than the copy I found myself elsewhere, but I have no way of knowing.
One advertisement that did offer some insight is one for Micro Switch SD Series, which indicated that production was expected in late 1974, and that SD Series was designed to compete with mechanical keyboard pricing (based on, it seems, projected 1975 pricing). The SD Series drawings date from 1975 and the oldest known SD Series keyboard was made in 1976. The advertisement suggests that the first keyboards would be delivered in 1975, which would fit.
This advertisement is now added to the SD Series page.
Thursday, 18th March
Joining the list of seemingly short-lived companies with no confirmed successful sales, is Fort Electronic Products, later known as FEP Associates. Their keyboard speciality was the Fero-Snap™ ferrite-based switch. With a company lifetime of under two years, the chances of finding one of their keyboards is slim to none, but somewhere out there, one of them may exist.
Wednesday, 17th March
Amongst the assortment of archived PDFs that Marcin Wichary sent me, that I had never noticed until today, was an announcement in Design News magazine from December 1983 for Maxi-Switch Series 6000 and 8000. This article was accompanied by an very poorly-scanned illustration of at least one switch type; comparing the text with what little could be made out of the illustration strongly suggested what 8000 Series was …
The relevant issue of Design News is carried by the Linda Hall Library, and after ordering a scan of the page in question from them (which they turned around promptly), the illustration turned out to depict exactly what I hoped it would:
- Maxi-Switch Series 6000 is now confirmed to be “Maxi-Switch vintage linear”: the illustration shows the two switch contacts in front of an assembled switch
- Maxi-Switch 8000 Series is the type that until now has been called “Maxi-Switch integrated dome”: the dome and the base plate with the contact pads can be clearly seen
I knew that Maxi-Switch were never sure whether “Series” should be a prefix or a suffix, but in this announcement, “Series 6000” and “8000 Series” are used verbatim.
The codes found on miniature elastic contact keyboards suggest either 8500 or 8700 series for those, which now fits in nicely with 8000 Series being the full-size elastic contact switches.
The encoding and output page is also updated with an intriguing discovery: an article from 1978 described a keyboard implementation where the keyboard matrix was treated as memory-mapped I/O, using a regular 8-bit microprocessor instead of a microcontroller.
Saturday, 13th March
For several years, the brands list has only covered manufacturers of switches and keyboards. More recently, it has been extended to cover the semiconductor manufacturers responsible for single-chip encoders. The component manufacturers list is now split into a column of its own, and is extended once again to cover a number of other manufacturers responsible for components, materials and equipment used in the keyboard industry, all backed by contemporary literature.
Covered thus far are companies responsible for keycap engraving machines (New Hermes Engraving Machine Corporation), PBT raw material (Celanese Corporation), tickers resembling the “solenoid” in IBM beam spring keyboards (Endicott Coil Company, Inc.), printed circuit boards (Photocircuits Corporation) and keyboard testing machines (Osawa & Company).
Monday, 8th March
Some time ago I wondered why Licon Series 550 was advertised in 1970 with so many wires passing through the switch. The answer is surprisingly simple: wired inductive encoding, in which the encoding of each switch is defined by which bit lines are passed through the ferrite cores. This seemingly short-lived idea may well have been unique to Licon; it seems that PCB-based encoding soon replaced it.
Sunday, 7th March
On the subject of forgotten products, here is another: Hathaway Drireed low-profile reed switches using a rotating magnet assembly. The rotating magnet design was first described by Hathaway in a patent for a tall reed switch filed in 1970, but their low-profile keyboard switch design (with a vertically diagonal reed to reduce height) filed two months later in January 1971. These switches used an interlocking system to avoid the need for a mounting plate, an idea that would become better known with the later Hi-Tek Dovetail Series design.
Also, another Futaba part number is now known: “MD4P-R”: this is for the blade stem version of MD-4. The “C” is now confirmed to mean a cross stem, implying that there is also an MD-4PC. An excerpt of the Futaba diagram along with the switch specifications can be seen in a Eagle Electric Co advertisement.
Friday, 5th March
There is a surprising number of keyboard manufacturers that have become completely forgotten with time, and whose products never seem to be encountered. One such company is the now-rediscovered Colorado Instruments, who in 1970 introduced clicky capacitive keyboards that used a metal dome as the movable capacitor plate.
Sunday, 28th February
Omron B3K has suddenly become a lot more complicated. Omron themselves–who for big name YouTube channels were willing to provide factory tours in both 2015 and 2019—refused to say a thing (about anything, not just B3K), such is my irrelevance. This has earned them a coveted place in the Keyboard Hall of Shame.
Андрей Студенцов (chromov113) has provided two interesting sets of photos, however. B3K-T13LN-L is a model used in the backlit Logitech G413, but lacks the light pipe found in all other models. B3K-T135 is a Creative PRES model. Note the lack of suffix on the model number: the reason for this is unclear, but the example he found is branded only by Omron. There is a separate B3K-T135C, listed in Omron Product Code Change AMP-Z-2007029, but whether that is a separate Creative-branded model or whether the “C” suffix here has a different meaning, is not known.
Omron Product Code Change AMP-Z-2007029—found on two websites of vendors who previously dealt with B3K (and now added on the B3K page)—lists four models: B3K-L135, B3K-T135 (used by Creative), B3K-T135-L and B3K-T135C. B3K-L135 could be linear (from the model number) and is shown with the same grey plunger as the linear Romer-G model B3K-L13L. A second type is depicted, possibly B3K-T135-L; like B3K-L135 this has only Omron branding. The “L” suffix here does not appear to denote Logitech, possibly similar to how B3K-T13LN-L has both “L” and “-L” present in the model number. (The three vendors who list B3K parts—TTI, Anglia and Arrow—were of no use. TTI did not even respond.)
The document also implies that lot numbers containing a “C” in the fifth position indicate Chinese manufacture, while those with “R” in the fifth position indicate Japanese manufacture. (Vintage Omron B2x switches uses “R”, as one might expect.) Inspection of the lot numbers on the Romer-G switches sold in China suggests that there may be production lines in both China and Japan, with a shift towards China as of the 1st of October 2020 as a reward for the pandemic.
Unfortunately, the more we discover about B3K, the more we realise that we do not know. It is a remarkably complex series considering that the mechanical keyboard market had collapsed, and is largely avoided by major switch manufacturers (with far too much reliance on an exponentially-growing list of secretive, muddled and often anonymous Chinese firms). One has to wonder whether any of these B3K models are used outside of the gaming market, such as for industrial control panels. This may never be known. Sadly we are likely to learn more about products from decades past than we are about a product currently on the market.
Monday, 15th February
A new listings page is available that shows tables of available keyboards as presented in historical publications. None of these tables are exhaustive; each one contains a selection of representative or interesting products on the market at the time. These tables help illustrate not just the brands and models that existed, but the types of sensing and encoding techniques in use at different times in the industry history. In some cases, the publication from which the table was obtained also illustrates and describes the working of these products.
The tables show a number of brands that are yet to be written up here: IKOR, Synergistics, Soroban, Teletype, Ultronic, Digitronics, Killian and Transducer Systems. Details of many of these product ranges are in the relevant publications or are in the many magazine back-issues scanned by Bitsavers and WorldRadioHistory.com. Further details on some of these will be forthcoming.
Saturday, 13th February
This time we stretch back a lot further, to the early days of computer keyboards, to the era when electromechanical keyboards were still being produced. A lot of interesting details on these keyboards were written up in the article Manual Input Devices in Computer Design, Volume 4 No. 12, December 1965, which is now added to the references page.
The Navigation Computer Corporation, also known as NAVCOR (later KDI Navcor) was an American electronics manufacturer whose product range included, over time, three different designs of reed keyboard switch. Their keyboards used diode matrices for encoding. Other keyboard types may have also existed: as with so many such brands, few examples are known. NAVCOR curiously took out a patent on the idea of switches with a sloped base, an idea that would be later used by a number of manufacturers including Raytheon, Veetronix, George Risk and Fujitsu.
Thursday, 11th February
Another early adopter of membrane keyboard technology was Chomerics. Alphanumeric products general manager Len Halio claimed in 1981 that Chomerics invented membrane switch technology in the late 1960s, although they did not apply it to full-size (alphanumeric or “QWERTY”) keyboards until long after Datanetics did. Until this point, their market was keypads, such as telephones, robotics and toys. There is no indication that any Chomerics keyboards have been found by anyone, but some must surely exist somewhere.
Sunday, 7th February
Having just uploaded the specifications of Oak Full Travel Membrane (kindly scanned in by TG3 Electronics), this seems a perfect time to upload an article from around the same time that describes the workings of Micro Switch’s own offering: SC Series capacitive membrane keyboards. It is not clear which of Oak and Micro Switch introduced membrane keyboards first, but both types seem to date from the start of the move to full travel membrane keyboards. (Datanetics batch-fabricated array is much older, but they found that discrete switches were more practical.)
When I first encountered suggestions of capacitive membrane keyboards from Alphameric, it seemed like some kind of a mistake, but the article from Computer Design from 1981 depicts and describes the operation.
Friday, 5th February
Photographs have turned up depicting the reed variant of SMK JM-0400 series and SMK’s elastic contact type (covered for the moment under JM-0400 in order to have somewhere to list it). The elastic contact switch is unsurprisingly identical to Maxi-Switch’s elastic contact type (as found in a few TRS-80 Model 4 keyboards and seen exactly once in a single photograph), right down to the green pigmentation of the rubber dome. This strongly suggests that SMK manufactured those switches for Maxi-Switch. With that said, no SMK branding is visible in either instance, nor any indication of where either switch came from. The images were uploaded without a single word of description and no permission to comment on them.
Wednesday, 3rd February
A Marylou Bassi-Dolmans, who used to work for the Clare and Pendar companies, recently contacted me. Following correspondence and further investigation, including going back through all the information that R Guzzetti posted to the Deskthority forum, the Clare and Pendar history page is now updated. There is more work to be done, but even already, the story is clearer than it was before.
Sunday, 31st January
I never realised that Samsung made one of the Amiga 500 keyboard types. I never thought of Samsung as a keyboard manufacturer at all. Strangely, the switch mechanism bears a strong resemblance to one of the designs in the patent that appears to cover Alps KFNR. Sadly there are no complete sets of photographs of this keyboard, and nothing showing any branding or part numbers.
The Amiga keyboards are clearly not yet fully documented on Deskthority. WMF-4E1Q2 is another barely-documented type, this time from the Amiga 600. This model appears to be NMB, but using conductive domes instead of the standard pressure domes.
Further research has turned up a number of extra single-chip keyboard encoders. These are EA2000, EA2007 and EA2030 from Electronic Arrays; MCS 1007, MCS 1008 and MCS 1009 from MOS Technology; and TMS 5000 and TMS 5001 from Texas Instruments. The point in time that single-chip encoders were introduced is still unclear. Thus far none have been seen before 1972.
Sunday, 24th January
Correspondence with MinebeaMitsumi has turned up a rather surprising fact: at the time that they bought Hi-Tek Corporation, they were already in the keyboard business, manufacturing “keyboards for IBM's high-end personal computers”, production of which began in September 1982, following an agreement in January 1982. Until now we have just assumed that the Model F—which is presumably the type they describe—was manufactured solely in the United States, but this seems not to be the case. D’Milo Hallerberg, who was employed at Hi-Tek at the time, confirms that Minebea were manufacturing IBM keyboards in Singapore. The production moved to Thailand in 1984, where production of Series 725 was also relocated.
Additionally, all of the remaining literature that Susan Kennedy provided to Benjamin Rockwell, and that he scanned in, is now uploaded to the Hi-Tek and Series 725 pages.
Friday, 22nd January
Magazine trawling has turned up a short article on a Cherry keyboard kit that used their magnetic-separation reed switches. The article briefly details how these keyboards are desired to be wire wrapped during prototyping; this was likely to have slightly pre-dated the introduction of LSI encoders and external encoding PROMs.
A new SMK JM-0400 page now exists to collect up any fragments of information that turns up about SMK’s interchangeable low-profile switch series. There is also a “stub” page for SMK JM-0200, which is some kind of unidentified keyboard switch, which could be anything from their tall reed switches to a short-travel keypad button. An advertisement mentioning “JM 0404” lists it alongside “JJ0019”; JJ-0019 or J-J0019 is some other unidentified series of keyboard switch or switch component.
Sunday, 10th January
Based on the information within the Geekhack topic Hall Effect Keyboard Sensing and Wiring Explained from dorkvader from January 2018 (discovered accidentally), the matrix scanning section of the Hall effect keyboards page is updated, reflecting an additional method of matrix scanning, and the implications that the different approaches have on rollover.
Saturday, 9th January
An illustration of Maxi-Switch 2700 series has finally turned up, in an advertisement in Electronics magazine from 1972. They are cylindrical reed switches with fins protruding from them. The advertisement is posted to the Maxi-Switch section and may help someone identify these switches should they show up somewhere.
Friday, 1st January2020 knowledge round-up
2020 has been a strange and ultimately disappointing year for reasons unrelated to the unexpected export from the Far East of something more dangerous than cheap electrical goods.
In terms of keyboard knowledge, it seemed fairly likely that 2020 was not going to top the level of revelation of 2019, and while this seems to be true, progress has continued in spite of everything. The big breakthrough was getting catalogues from RAFI in March for their RC 72 and magnetoresistive types, the latter being to date the only known example of magnetoresistive switches. This was the first but by no means the last instance of finding details that seemed highly unlikely to be found, showing once again that so long as you keep searching, you will find.
The RAFI discoveries then led to an in-depth investigation of German Hall sensors, not least because RAFI were offering a variety of output options not covered by the HFO B 461 G sensors that we have encountered thus far. Discussion with various people in Germany and examination of various websites and catalogues has allowed me to list out both the Siemens Hall sensor ICs and the HFO Hall sensors derived from them, although the early history of the Siemens types remains poorly understood.
Several years ago, Meryl Miller offered me an assortment of switches, and I selected just the keyboard types for myself and Jacob Alexander. More accurately, I selected the ones that I believed were keyboard switches, missing the fairly obvious Micro Switch KB reed switch (which was a solder terminal type, rather than the quick connect alternative that is all I have been able to obtain to date). Less obvious was a curious contraption that turned out to be Fujitsu FES-2. The real shame was in passing up a Raytheon keyboard switch. Extensive trawling through old electronics and computing magazines at Bitsavers turned up considerably more detail on these switches than expected, giving us the identities of KBSM for the mechanical switches and KBSR and KBFR for the reed switches. (In theory, KBFM—mechanical with a flat base—should also exist, but no sign of it has been discovered to date.) Only two KBSM switches have ever been seen: the one that Meryl has since discarded, and one that had already sold on eBay, from a seller too mean to permit the now-redundant photos to be published here.
Perhaps the most surprising discovery of all, was the names of several Stackpole series names, specifically KS-200 for the high-profile arrays, KS-200E for the low-profile arrays and the interlocking discrete switches, KS-500E for low-profile membrane keyboards, and finally KS-600E for the plate-mounted discrete switches derived from KS-200E. No mention has been found to date of a KS-100.
Keyboard enthusiasts are frequently acquainted with the method by which modern keyboards operate: the switches are wired in a grid (or matrix) and scanned by firmware stored within a microcontroller, with the key definitions stored within the firmware. Far less is known about the workings of keyboards going back to the 1960s, and the many ways of implementing a keyboard before the late 1970s when it started to become cost-effective to use a microcontroller. Many of the early techniques are now covered on the encoding and output page, itself still a work in progress as more details emerge. As part of this endeavour, Micro Switch KB encoding switches are now detailed on their own page; these pre-date the reed switches by a couple of years or so, something still in line for documenting according to literature.
Other discoveries made in 2020 include:
- The Hi-Tek switches in the UB80-01AA keyboards are licence-made by Cherry in their US factory, arranged by DEC, as explained by Peter Cherry. This ties in with DEC arranging for Tontec to produce Hi-Tek array mouldings in Hong Kong, possibly with some other company producing the completed switches for those specific VT-100 keyboards.
- We have the first non-Logitech part number within Omron B3K series, from José Soltren, which has helped with understanding the part number format for B3K. Now all that remains is to obtain the switch part number from a Creative PRES switch.
- There is a possibility that the keycaps on most BBC Microcomputer keyboards are the long-lost Signature Plastics SS series.
- The internal contact arrangement of Cherry M75–M78 is now known, although it remains to be documented; specifically, the design is almost the same, but the half-width contacts are arranged in side-by-side pairs. This allows two contact pairs in an alternate action switch (with the alternate action mechanism on the rear of the plunger), or four contact pairs in a momentary switch.
- Although Oak Series 400 was already tentatively identified, the smaller type was not; these are now known to be Oak Series 475, again identified from trawling old magazines.
- Another magazine find (from scans provided by Marcin Wichary) gives us Series 555 for the “Early Ⅱ” and “Early Ⅲ” styles of Licon/Cortron ferrite core switches, leaving “Early Ⅰ” to be the original Series 550. Confusingly, we now know that a Series III existed, but from the description, this is not the tall switches in 35-* keyboard models. Just as confusingly, the DIN-compliant switches seemed to be split between two separate series: FC-2550 and FC2500 (with only the former having a hyphen). Details on both series remains too vague to understand how they differed, but the suggestion seems to be that FC-2550 had model numbers beginning 25-5* while FC2500 had model numbers beginning 25-0*, something that cannot be proven one way or the other due to how few examples have been properly documented by their owners.
- The confusion around Micro Switch CT and its relationship with ST is now explained: the original two series were capacitive membrane SC and contact membrane CT. ST silent tactile keyboards superseded both, replacing the click spring with a rubber dome, and providing both membrane types under a single series.
- Electronic Engineers Master from 1989–1990 provides a list of features and part numbers for Marquardt Series 6184, indicating that the series included alternate action, tactile feedback and a choice of 2.5 mm and 4 mm travel. Later, a click-tactile type would show up in California, which for now is being presumed to be the tactile type (something Marquardt have neither confirmed nor denied). The click mechanism is something not seen before, and is illustrated on the Series 6184 page.
- Several more MEI T-5 Series subseries are now known, from old advertisements.
- Maxi-Switch “vintage linear” may be 6000 Series, although this remains to be formally confirmed. These switches are now almost certainly made by SMK or made using tooling licensed from SMK, which explains why the “integrated dome” type bears a very strong resemblance to another SMK series.
- It now seems likely that the Fujitsu “sheet keyboard” system is FES-3001 while the “typewriter” form (the full travel type) is FES-301. Following the introduction of DIN ergonomic standards, a lower-profile version of FES-301 was adopted, which is FES-301E (Fujitsu provided this series name and indicated that “E” denotes “ergonomic”).
- Another magazine find was a brief advertisement for SMK JM-0400 series. J-M0404 and the heretofore unobserved J-M0409 fall within this overall series. Most interestingly, JM-0400 included reed switches. We already knew that SMK produced reed switches, but not that they miniaturised them. It seems that SMK filed few patents, or they are still awaiting digital recording, as very little showed up on J-PlatPat for SMK, with no reed or integrated dome types appearing at all.
- Just as understanding of Alps was starting to improve, 2020 has dealt it some blows. Jacob Alexander has found a new Alps reed type, this time classified as SCF instead of SCB. This would suggest that even in the S-code era, each series had its own identity, but that does nothing to clear up the confusion around CH and SCH. An old advertisement for Alps switches and keypads gives a totally different series identity, in a way that does not make sense, but with the spring bridge switches considered to fall under SCH being listed as AKC.
- The origin of Cherry MY is now much better understood. The different types remain a mystery; even Günter Murmann was unable to recall anything about them.
- There is now clear evidence that HP bought “mousetrap” switches from Cherry; more details are given on the new Cherry Series S31 page.
All things considered, 2020 has fared significantly better than it could have, and with luck 2021 will be at least as bountiful.