Licon and Cortron (ITW)
- Switch types
Cortron was created as a spin-off from Licon, as a dedicated keyboard manufacturer, as noted in the Series 555 advertisements in Computer Design magazine in September and December 1976 (see Documentation below). Cortron was apparently later sold to Amkey, who went on to merge with Cortron, with the new company taking Cortron’s name.
This page is at present an overview of ITW Licon and early ITW Cortron keyboards; Cortron’s modern product range is not covered here. Details on the product families is fairly scarce still.
The general pattern of the part numbers seems to be as follows:
|Keyboard part||PCB part||Possible series||Switch type|
|55-□xxxxx||80-55xxxx||Series 550?||Ferrite core, original design|
|55-5xxxxx||80-55xxxx||Series 555||Ferrite core, low profile|
|35-xxxxxx||80-35xxxx||Ferrite core, intermediate|
|25-□xxxxx||80-25xxxx||Series FC-2500?||Ferrite core, DIN-compliant low-profile|
|25-5xxxxx||80-25xxxx||Series FC-2550?||Ferrite core, DIN-compliant low-profile|
The specific breakdown between series is only a guess at this time, as there are just too few examples of anything except Series 555. In particular, no linear DIN-compliant ferrite core types have ever been found, and most DIN-compliant ferrite keyboards are not properly documented. No keyboards from before Series 550 have been documented; one example was listed on eBay with photos that did not clearly show the switches, but that listing is now long gone.
Note that the third and fourth digits of the PCB part number correspond to the first two digits of the keyboard part number.
The table below provides an overview of relevant Illinois Tool Works patents, taken out on behalf of Licon and Cortron for keyboards. Several patents (thus marked) all derive their priority from application US14490271A (filed in May 1971), themselves filed in 1972, 1974 and 1981, with one of the patents filed in 1974 not being granted until 1985.
|US 3638221||Solid-state keyboard||1969-11-24||1972-01-25||Wired inductive encoding for Series 550|
|US 3612241||Keyboard switch construction||1970-03-30||1971-10-12||Series 550 keyswitch|
|US 3698531||Solid state switch||1970-10-26||1972-10-17||Sextuple-magnet rollover-capable ferrite core switch; possible variant of Series 550|
|US 3691333||Alternate action mechanism||1971-03-19||1972-09-12||Series 550 alternate action mechanism|
|US 3714611||Solid state switch construction||1971-11-18||1973-01-30||Low-profile version of the original Series 550 design|
|GB 1380282||Keyboards||1972-05-17||1975-01-08||Priority to US14490271A, 1971-05-19, seemingly unpublished|
|US 3824362||Alternate action switch mechanism||1973-05-23||1974-07-16||Series 555 alternate action switch, as seen in the HP 02645-60023 ca. 1978 as ferrite core|
|US 3882295||Tactile feedback switch mechanism||1973-10-04||1975-05-06||Series 555 tactile feedback mechanism|
|US 4517553||N-Key rollover keyboard||1974-04-04||1985-05-14||Priority to US14490271A, 1971-05-19, seemingly unpublished|
|US 3902032||Electrical switch with improved contact structure||1974-06-07||1975-08-26||Mechanical derivative of Series 555 (this patent references Hi-Tek’s patent filed two years earlier)|
|US 3918051||N-key rollover keyboard||1974-06-10||1975-11-04||Priority to US14490271A, 1971-05-19, seemingly unpublished|
|US 3978474||Keyboard with n-key lockout and two-key rollover protection||1975-07-15||1976-08-31|
|US 4099176||Magnetic key switch having a removable support assembly||1974-11-20||1978-07-04||Series 555 (priority date 1974-05-30)|
|US 4028696||Double depression magnetic keyswitch||1976-01-26||1977-06-07||Series 555 double action switch|
|US 4017850||Magnetic keyswitch with two-piece support assembly||1976-02-02||1977-04-12||Series 555 style B|
|US 4071719||Keyboard switch assembly having actuator interlocking keyboard shift and shift lock and release mechanism||1976-07-22||1978-01-31||Mechanical shift lock for Series 555|
|US 4227163||Electrical keyswitch||1979-03-05||1980-10-07||“Intermediate” ferrite core and mechanical switches|
|US 4263582||Keyboard with an externally programmable repeat rate and repeat delay rate counter||1979-08-24||1981-04-21|
|US 4295012||Secretarial shift mechanism for an electric keyboard||1980-02-04||1981-10-13||Mechanical shift lock for “intermediate” switches (both ferrite core and mechanical are depicted here)|
|US 4390866||Keyboard with electronic hysteresis||1981-02-19||1983-06-28||Priority to US14490271A, 1971-05-19, seemingly unpublished|
|US 4704601||Keyboard data entry system with hysteresis||1985-06-27||1987-11-03|
These are solid state switches which are sensed by controlling whether or not current will pass inductively from one wire to another through a ferrite core. They have been referred to as “magnetic valve” switches, but in advertisements from Licon and ITW, they are described as “ferrite core”. Here, the magnet in the plunger suppresses the inductance, and when the plunger is depressed, the inductance is enabled and the key will be detected. These solid state switches are almost the same age as Micro Switch SW, which is a Hall effect solid state keyboard series.
In most cases, the older switches are all Micro Switch mount. The DIN-compliant types use a German-style snap on mount, the compatibility of which with German switches is not confirmed. However, HP 264XX Data Terminal keyboards use early ferrite core switches with a cruciform mount, whose keycaps fit onto Alps Series KCC switches:
The technical literature for the simplified keyboard from this series—from August 1976—gives only HP part numbers for the “LICON” switches used.
Ferrite core keyboards are normally linear. Keyboards made for the Trendata 4000 use a patented click feedback system, found in US patent 3882295 filed in October 1973. The patent date suggests that the click feedback system was added to Early Ⅱ switches, but the only known example (three keyboard modules from the Trendata 4000) is of Early Ⅲ switches. The patent is titled “Tactile feedback switch mechanism” but it does specifically generate both audible and tactile feedback. The tactile feedback was added to simulate the feel and sound of “mechanical” switches, to avoid operator error arising from a lack of feedback that a key actuated.
This is a capacitive keyboard that uses a leaf spring under each key instead of a foam pad with foil attached. The design is very similar to Digitran metal leaf capacitive switches. The example below has a series of patents on the label but the switch patents thereon are for ferrite core switches.
This is a series of tall switches introduced around 1970; they can be seen advertised in Modern Data, December 1970 (see Documentation, below), the same year that the patent was filed. The rated lifetime was 25 million cycles. These switches (at least in the form patented and advertised) do not use a PCB. Instead, a ferrite core is fitted to each switch, and one or more windings are fed through the cores. Unlike later designs, which only ever used a single wire for each winding, these switches were illustrated as using multiple wires for the windings.
Licon advertised a wired inductive encoding system where the encoding was defined by which sense wires passed through each ferrite core. This principle is covered under US patent 3638221 “Solid-state keyboard” filed in November 1969. The general principle is illustrated in the diagram below. The diagram does not cover the magnetic suppression of the induction cores; only the encoding technique is depicted. The advertisement in Modern Data shows many wires passing through the core, in accordance with the written description of the encoding used. The ferrite core wiring was automated in the factory.
Within a year or so, the switch size was drastically reduced, as shown in a fresh patent. Whether these lower-profile switches continued to be described as Series 550 is not known. A 1971 advertisement in Electronic Design describes them, but does not name the series as the previous advertisement did.
Series 555 is a low-profile ferrite core design. These switches are specifically designed to be soldered to the PCB. The ferrite core assembly is a separate part that is soldered to the PCB, allowing the plunger assembly alone to be removed and replaced when damaged. Series 555 switches can be seen in an advertisement in Computer Design in September 1976 (see Documentation below), but the patents go back to 1973 and the oldest example observed to date is from 1975. There are two styles of Series 555 switch, both covered under US patent 3902032 “Magnetic key switch having a removable support assembly”, and both types can be seen in the advertisement.
Although these keyboards are covered by a number of patents, most of these keyboards are marked as being covered by US patent 3035253, filed by George C Devol on magnetic storage.
This series includes a double-action switch that uses two ferrite cores. These switches are much taller than the standard momentary types, and while one could be forgiven for thinking that they belong to Series 550, they were patented after the standard Series 555 switches. These double-action switches can be found alongside standard-height momentary switches in the HP 9845 workstation keyboard.
This style is rare. This is so far only known from a Univac Uniscope 100 keyboard.
This is the standard form of Series 555, widely encountered, with examples ranging from the mid-1970s to the mid-1980s.
Series 54 “solid-state” keyswitches got a brief mention in Computerworld, 31st of May 1976. They may not be computer keyboard switches: the details given are very brief. These may not be ferrite core either, but it seems likely that they would be. This series was further mentioned in the NCC 1976 booth announcement for Licon, which refers to “series 54 Superswitch II standard, tactile, alternate action, double depression, incandescent, and LED keyswitches.” These switches are not mentioned. It’s curious that the term “SS3” is later used for Series III switches; possibly those are “Superswitch 3” not “solid state 3”.
In Interface Age, August 1981 on pages 132 and 134, there is a brief mention of the Cortron CP-4550 keyboard, which uses the “CP-4550 keyswitch”. This switch is said to give an “exceptional, true linear feel” and is “environmentally superior to foam pad design approaches”. The rated lifetime is in excess of 100 million cycles.
The Recent Microsystems Announcements from Computer magazine, June 1981 cites this model as being a “Solid-state, capacitance unit”, with a unit price of $45 in volume quantity ($127 in June 2019).
The comparison with foam and foil indicates that it uses a different mechanism, with the Digitran-like capacitive system in model 45-500008 being the likely candidate considering that both use “45” as part of their respective identities.
US patent 4352144 filed in January 1981 depicts a metal leaf capacitive arrangement where the plunger contains a flexible prong that provides overtravel. However, model 45-500008 listed below (a Xerox 820-II keyboard) uses a Digitran-like design where a portion of the capacitive leaf serves to provide the overtravel instead.
These are surprisingly tall switches considering that they are a complete redesign produced around 1979. US patent 4227163 “Electrical keyswitch”—filed in March 1979—covers these switches, and it appears that the same shell supports both ferrite core and mechanical contacts. All discovered examples to date have been the ferrite core type.
The only identifying marks of these keyboards is that the internal part numbers take the form 35-5xxxxx. As with Series 555 keyboards, these keyboards are also marked with US patent 3035253.
Series III was advertised in Computer Design, July 1978 (and other issues) on page 107. No magazine scan to date has sufficient quality to make out the design of the switch, with the details typically lost to JPEG artefacts. The SS3 switches in Series III keyboards are described as having “fewer parts” and being “lower profile”, despite there being no known switch type to have been introduced around 1978 (the copyright date within the advertisement). The switches bear a faint resemblance to Series 555. They are certainly nowhere near as tall as the “intermediate” type that was patented around that time.
Series III is advertised as having a lifetime of 100 million cycles.
The meaning of “SS3” is not given, but it could denote “Superswitch III” considering that a “Superswitch II” existed (Series 54).
Series FC-2550 is a DIN-compliant ferrite core design, advertised in 1981. These too are advertised with a 100 million cycle lifetime. FC-2550 switches are stated to have “true linear feel”.
In Computerworld, 28th March 1983, Illinois Tool Works advertised Series FC2500 keyboards. These are described as “low-profile” and offered linear and tactile options. In Computerworld, 2nd July 1984 it is also noted that these keyboards were reported to meet a 30 mm height requirement. Series FC2500 is a candidate for the low-profile type that was later manufactured by Devlin in the UK, as currently there are no indications of FC-2550 being tactile. In neither case were any illustrations provided. An illustration of a switch is shown in Computer Design in May 1983 (see Documentation below), which is a good match for the 25-50xxxx keyboards.
The article La Tastiera in the Italian magazine Selezione di elettronica e microcomputer from June 1985 contains the following description of Series FC2500 on page 59:
Tastiera ITW Cortron con feedback sia tattile che visivo. Il modello FC2500 emette un suono simile a quello di un grillo quando viene premuto un tasto. Essa adotta la tecnologia a ferrite; il feedback tattile è fornito da interruttori a cupola.
This translates to:
ITW Cortron keyboard with both tactile and visual feedback. The FC2500 model emits a sound similar to a cricket when a key is pressed. It adopts ferrite technology; tactile feedback is provided by dome switches.
Computer Weekly (supplement) 5th of January 1984 announced the launch of an unspecified series of Cortron ferrite core keyboards, noting:
The low profile keyswitch measures 17.1 mm high with keytop, 21.9 mm, and has a full travel of 4mm. Keyswitches can be provided with linear or tactile feel.
It seems strange that FC-2550 was seemingly advertised before FC-2550. Because so few ITW DIN-compliant keyboards have been properly documented, there is no way at present to determine whether FC2500 and FC-2550 use different part number prefixes.
The following is a list of known Licon and Cortron keyboard models with both the switch type and part numbers known, arranged in date order:
|Part number||PCB number||Manufacturer||Switches||Serial||Date||Notes||Reference|
|55-100007||80-550461||Licon||Ferrite core, uncertain type||7131||eBay|
||Licon||Series 555 style B, tactile||025470||7514||Trendata 4000 keyboard||Deskthority|
|55-500003||80-550782 REV G||Licon||Series 555 style A||005315||7585||Univac Uniscope 100 keyboard||Deskthority|
|55-500081||80-551178 REV.D||Licon||Series 555 style B, tactile||000933||7605||Trendata 4000 keyboard||Deskthority|
|55-500081||80-551178 REV.D||Licon||Series 555 style B, tactile||51439||7610||Trendata 4000 keyboard||Deskthority|
|55-500140||80-550932 REV F||Licon||Series 555 style B||59710||7621||Unidentified keyboard||eBay|
|55-500161||80-551093 REV. J||Cortron||Series 555 style B||293869||7934||Raytheon model 6101-04||Deskthority|
|55-500056||80-551101 REV D||Cortron||Series 555 style B||346831||8004||Unspecified Raytheon model||Deskthority|
|55-500135||80-551478 REV. B||Cortron (Licon PCB)||Series 555 style B||367693||8012||Double-shot Japanese keycaps||Flickr|
|55-500539||80-551879||Cortron||Series 555 style B||370322||8016||Xerox X998; part of the case is from 1982||Flickr|
|55-500219||80-551655 REV.B||Cortron||Series 555 style B||406859||8030||Unknown origin||imgur.com|
|35-500059||80-350072 REV. B||Cortron||Ferrite core, intermediate||455684||~1980||Unidentified Univac keyboard||Deskthority|
|55-500219||80-551655||Cortron||Series 555 style B||8107||Unknown origin||eBay|
|35-500095||80-350128 REV. A||Cortron||Ferrite core, intermediate||526148||8133||Unidentified Univac keyboard||Flickr|
|45-500008||?||Cortron||CP-4550||1009281||8314||Xerox 820-II keyboard||q7.neurotica.com|
|?||80-350128 REV. A||Cortron||Ferrite core, intermediate||?||~1983||Prime/Pr1me ESA 5146 keyboard||Deskthority|
|55-500582||80-551646 REV. C||Cortron||Series 555 style B||1029395||8406||Unidentified keyboard||Deskthority|
|25-500035||80-250092 REV C||Cortron||Ferrite core, DIN-compliant, tactile||1019362||8438||Xerox 820-II keyboard||Flickr|
|25-500200||80-250177 REV. H||Cortron (Taiwan)||Ferrite core, DIN-compliant, tactile||112122||8630||Burroughs B25 K1 AB||Deskthority|
|35-500083||?||Cortron (Mexico?)||Ferrite core, intermediate||1004568||8747||Unidentified keyboard, possibly HP||GovPlanet|
The serial numbers appear to be monotonic, but on at least two occasions ITW seem to have started a new numbering range. The Taiwan-made example has a serial number from a separate system.
The documents below were all scanned by Bitsavers.
- Licon Series 550 keyboards advertisement, Modern Data, December 1970, page 8
- Licon low-profile keyboard advertisement, Electronic Design, November 25 1971, page 101
- Licon booth announcement for NCC 1976 including a mention of series 54 Superswitch II, Computer Design, Vol. 15 No. 5, May 1976, page 141
- Cortron advertisement, Computer Design, September 1976, page 5: covers the spin-off from ITW, and depicts Series 555 (cleaner scan from November)
- Cortron FC-2550 advertisement, Computer Design, May 1981, page 155
- Cortron CP-4550 advertisement, Computer Design, May 1981, page 157
- Cortron FC2500 advertisement, Computer Design, May 1983, page 76