Jump to page content

Licon and Cortron



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
45-5xxxxx 80-45xxxx CP-4550 Capacitive leaf
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.

Patent Title Filed Published Product
US 3612241 Keyboard switch construction 1970-03-30 1971-10-12 Series 550 keyswitch
US 3714611 Solid state switch construction 1971-11-18 1973-01-30 Low-profile version of the original Series 550 design
US 3824362 Alternate action switch mechanism 1973-05-23 1974-07-16 First-generation alternate action switch, as seen in the HP 02645-60023 ca. 1978 as magnetic valve
US 3882295 Tactile feedback switch mechanism 1973-10-04 1975-05-06 Tactile feedback mechanism for first-generation switches
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 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 4295012 A Secretarial shift mechanism for an electric keyboard 1980-02-04 1981-10-13 Mechanical shift lock for “intermediate” switches (both magnetic valve and mechanical are depicted here)

Switch types

Ferrite core

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.

Capacitive leaf

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.


Series 550

This is a series of tall switches introduced around 1970; they can be seen advertised in Modern Data, December 1970, 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.

Series 555

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, November 1976 on page 149. There are two styles of Series 555 switch, both covered under US patent 3902032 “Magnetic key switch having a removable support assembly”.

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.

Style A

This style is rare. This is so far only known from a Univac Uniscope 100 keyboard.

Style B

This is the standard form of Series 555, widely encountered, with examples ranging from the mid-1970s to the mid-1980s.

Series 54

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.


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

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.

Series FC-2550

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”.

Series FC2500

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. There is a good chance that Series FC2500 is the low-profile type that was later manufactured by Devlin in the UK, as the description and date of introduction suggest DIN-compliance. In neither case were any illustrations provided.

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
55-500081 80-551178 REV.B 4 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 1019362 8438 Xerox 820-II keyboard Flickr
25-500200 80-250177 REV. H Cortron (Taiwan) Ferrite core, DIN-compliant 112122 8630 Burroughs B25 K1 AB Deskthority

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.