Jump to page content

Licon and Cortron (ITW)



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
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 555 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.

Patent Title Filed Published Product
US 3638221 Solid-state keyboard 1969-11-24 1972-01-25 Wired inductive encoding for Series 550
US 3638222 Flux gate switch 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 4352144 Capacitive keyswitch with overtravel plunger mechanism 1981-01-21 1982-09-28 CP-4550 capacitive keyboards
US 4480937 Breakaway leafspring actuated keyswitch apparatus 1982-08-30 1984-11-06 Unknown snap-action leaf spring mechanical type
US 4453063 Keyswitch configuration with torque rod holder 1983-08-03 1984-06-05 FC-2550/FC2500 integrated stabiliser clip
US 4535210 Keyswitch stabilizing device 1984-04-18 1985-08-13 FC-2550/FC2500 keycap stabilisation
US 4704601 Keyboard data entry system with hysteresis 1985-06-27 1987-11-03

US patent 4453063 says of the keycap mount, “This sleeve is not illustrated since the key cap and the switch actuator are old.” Likewise, of the switch implementation, “Various details of structure of the switch are not shown since they are old and are of no consequence to the present invention.” As such, it appears that the DIN-compliant design (FC-2550 and/or FC2500) were not patented, with the means of reducing the size of the switch not deemed to fall outside of the existing patents.

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 within the keyboard enthusiast community, 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 around 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 Golden Touch switches. The examples below have a series of patents on the label but the switch patents thereon are for ferrite core switches.


At least two switch designs were also patented with mechanical contacts. So far, no ITW mechanical keyboards have been discovered.


It appears that keyboards and switches were assigned separate series. Switch series names were likely all two-digit numbers, while keyboard series used three and four digits. The mechanical switches may have had alphanumeric codes, with Cortron suggesting something like “E3” or “E4”.

Series 550

Series 550 is presently the oldest known keyboard series. These keyboards, introduced around 1969, used tall switches. The oldest description of this series is from October 1969, and the patent for the encoding technique was filed in November that year. The oldest (and only) known depiction of the switches is from an advertisement in Modern Data in December 1970. 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, one per output bit. 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.

In a letter to the editor, published in Electronics magazine on the 1st of March 1971 (page 8), John Pfeiffer from Licon offered a correction to a claim made in the In key with computers panel of the article Capacitive keys, simpler circuits add up to reliable keyboard from the 7th of December 1970 issue, where Licon’s keyboards were said to use TTL encoding. Licon countered:

… the Licon keyboard technology was misrepresented. One of its most important features is encoding at the switch, which allows the customer to choose standard or custom encoding formats without special tooling and eliminates the need for a diode matrix or MOS chip.

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. Electronic Engineer magazine’s “this is your keyboard reference” (AKA Keyboard Selection Guide) from September 1971 (scanned by Bitsavers) depicts the lower-profile switches, which still have have wires routed through the ferrite cores, rather than soldered leads. Both the September 1971 chart and November 1971 patent show only a single pair of wires passing through the core, suggesting that the wired encoding technique was no longer in use at this point, replaced by matrix scan.

Super Switch

Licon’s advertisement in Electronic Engineers Master 1973–74 Section 2000 is for an ASR33 keyboard with “Super Switch” ferrite core switches. From the top of the mounting plate to the bottom of the PCB, the height is shown to be 0.66″; this is effectively the distance for a Series 555 keyboard, suggesting that “Super Switch” could denote a switch series used in Series 555 keyboards.

Series 555

Series 555 keyboards use low-profile ferrite core switches. These switches are specifically designed to be soldered to the PCB, although this change appears to pre-date Series 555. 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. Patents for Series 555 date back to 1973, and the oldest advertisement discovered to date for Series 555 is from Computerworld, December 1972. A later Series 555 advertisement from Computer Design in September 1976 shows that both of the switch styles depicted in US patent 3902032 “Magnetic key switch having a removable support assembly” are used in the same keyboard series.

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.

Series 555 secretarial shift can be seen in the Xerox X998 keyboard.

Style A

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

Style B

This is the standard form of switch used in Series 555 keyboards, which is widely encountered, with examples ranging from the mid-1970s to the mid-1980s. These switches appear to be Series 54 Superswitch II; it is not known whether Style A also falls under Series 54.

Series 54

Series 54 “solid-state” keyswitches got a brief mention in Computerworld, 31st of May 1976. 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 depicted. It’s curious that the term “SS3” is later used for Series III switches; possibly those are “Superswitch 3” not “solid state 3”.

Indications are that these switches are the “Style B” type in the Series 555 keyboards. The following types are known; whether they are all keyboard switches, is not known, as some were located only via NSN information:

Part no. Type Customer part NSN Used in
54-0006-1-RED 5930-01-329-7836
Momentary; mount not observed HP 3101-1899 5930-01-049-8288 HP 264X (1976 service manual)
54-0013 Alternate action; mount not observed HP 3101-1900 5930-01-050-0561 HP 264X (1976 service manual)
54-0072 5930-01-040-8747
54-0073 5930-01-058-5024
54-0202 Alternate action; appears to be Cherry 12 mm mount HP 3101-2136 5930-01-095-0443 HP 264X (1981 service manual)
54-0203 Momentary; appears to be Cherry 12 mm mount HP 3101-2137 5930-01-095-0444 HP 264X (1981 service manual)
54-0440 5930-01-260-6460
54-0441 5930-01-244-7388

Series 56

Series 56 appears to be the keycaps that went with Licon Series 550 keyboards, based on a leaflet included with sample parts that may date to 1976. These are double-shot moulded keycaps, with the material given as “SAN copolymer”, denoting styrene-acrylonitrile resin. The slot in the keycap that accepts the plunger is shown to be 0.030±002″ wide and 0.250±0.002″ front-to-back, with a vertical depth of 0.340″ minimum. The keycaps are 0.716″ square and 0.477″ tall.

It would appear that Licon offered these keycaps for sale separately.


CP-4550 is a metal leaf capacitive system. The original design is covered by US patent 4352144 “Capacitive keyswitch with overtravel plunger mechanism”, filed in January 1981. The switch as illustrated in advertisements in Computer Design magazine in April and May 1981 exhibits a notable difference from the patent: the capacitive leaf has a tongue portion for the plunger to engage. This is effectively the same design as Digitran’s Golden Touch capacitive keyboards, that Cortron appear to have copied.

Cortron CP-4550 is mentioned briefly in Interface Age, August 1981 on pages 132 and 134, and is said to use 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 $45 price also appears in the Computer Design magazine advertisements.

As with many other capacitive designs, CP-4550 keyboards have an external return spring visible under the keycap. This spring is however held captive by the plunger and will not be misplaced after removing a keycap. As with Series 555, the keycap mount appears to be Micro Switch.

All CP-4550 keyboards observed to date appear to have Comptec SA family keycaps.


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 in July 1978 (and in later issues). 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 may bear a faint resemblance to those used in Series 555 keyboards, but this is not clear. 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 switches are said to be 0.5″ (1.27 cm) from the mounting plate to the bottom of the keyboard. This is pretty much the distance from the bottom of the mounting plate to the bottom of the terminals on the “intermediate” switches, assuming that “keyboard” in this context refers to the internal assembly. Switch travel is given as 0.150″ (3.81 cm).

The meaning of “SS3” is not given, but it could denote “Superswitch III” considering that a “Super Switch” keyboards and “Superswitch II” keyboard switches existed (Series 54).

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. 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 FC2500. 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
? ? ? CP-4550 ? ? Xerox 860 IPS CAT-less keyboard eBay
45-500008 80-450025 Cortron CP-4550 1007817 8311 Xerox 820-II keyboard (Xerox part 110S80564) deskthority
45-500008 ? Cortron CP-4550 1009281 8314 Xerox 820-II keyboard (Xerox part 110S80564) q7.neurotica.com
? 80-350128 REV. A Cortron Ferrite core, intermediate ? ~1983 Prime/Pr1me ESA 5146 keyboard Deskthority
45-500056 ? Cortron CP-4550 1000394 8326 Unidentified, possibly Univac coronthica.com
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.

Note that the controller chips on newer keyboards all appear to have part numbers in the range 80-552xxx, regardless of keyboard series. Series 555 keyboards have controller or encoder chips with part numbers in the same 80-551xxx range as the keyboard PCBs.

Two models, 55-500161 and 55-500135, use a Deltrol Controls 100C Series clapper solenoid as a clicker. The underlying device is a conventional solenoid, but Deltrol only have “Core Tron” listed as a customer of this long obsolete part, and it may have been custom ordered with a modification that makes it operate solely as a clicker.


The material below was scanned by Bitsavers unless otherwise noted.