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Key Tronic

United States



Key Tronic Corporation was founded in 1969 by Lewis G Zirkle (1915–2005). Lewis Zirkle previously managed the Clare-Pendar plant in Idaho: in 1966, following C. P. Clare & Co.’s acquisition of Pendar, he was named vice president and general manager, under president C E Fisher. For a time, Key Tronic was the world’s largest keyboard manufacturer, with 2800 staff in Spokane.

It appears that Advanced Input Devices was founded by a former Key Tronic employee, John Overby. According to the New York Times article “Advanced Input’s I.B.M. Coup” from 26th November 1983, he and many others at Advanced Input Devices previously worked for Key Tronic.

In 1993, Key Tronic bought Honeywell’s membrane keyboard product range. Hall effect keyboards may have remained with Honeywell.

Now branded “Keytronic”, the company appears to have finally left the keyboard market and now provides contract manufacturing.

Keyboard types

The history of Key Tronic’s product range is not well understood. This situation is made worse by the apparent complete lack of series names for their switch technology, and how Key Tronic appear not to have ever sold discrete switches (even though single-unit switches did exist). The oldest patent was filed in December 1970 and relates to plungers that appear to from their reed switch keyboards.


Key Tronic’s reed switch keyboards used multi-gang switch modules, in various sizes including four-unit, five-unit, six-unit and even single-unit (for keys such as space bar). These modules are secured to the PCB using screws. Custom modules were produced with unused key positions or custom spring weights in specific positions. Broadly, there are two designs. In most instances, the reed capsule is fed through the PCB from below via a circular hole. This approach allows the reed capsule to be replaced without needing any other disassembly work. There are also keyboards where the reed assembly is inserted into the PCB from above. Maxi-Switch 2900 Series reed keyboards use a construction almost identical to that of Key Tronic, including the ability to swap out the reed capsules from below.

In the 1977–78 Electronic Design Gold Book, Key Tronic gave a lifetime of over 100 million cycles for their reed switch keyboards. No lifetime was given for the two capacitive types in this instance.

Various photographs of the switches can be found on the Key Tronic magnetic reed page on the Deskthority wiki.

Key Tronic also made low-profile reed switches using plunger modules externally identical to those of their capacitive keyboards. This arrangement has the reeds placed horizontally on the PCB, with a hole below each reed capsule that may improve clearance. This switch type can be see in an unidentified industrial keyboard from around 1990.

All known Key Tronic reed keyboards are linear.

Foam pad capacitive

Key Tronic are best known for their foam pad capacitive keyboards. The earliest-known Key Tronic foam pad type capacitive type shared the same multi-gang module style as the reed types. Presently the year of introduction of these capacitive switches is not known, but they were in existence in the 1970s. Maxi-Switch’s CAP-TRON keyboards are likewise similar to the Key Tronic reed keyboards, but Maxi-Switch used a special shape of PCB pad and corresponding special shape of foam and foil pieces, while Key Tronic used more conventional circular foam and foil and half-moon PCB pads.

Key Tronic placed the following advertisement in the 31st May 1976 edition of Computerworld:

Keytronic Sets C Series Debut

NEW YORK – The introduction of the C Series of solid-state keyboards from Keytronic Corp. will be spotlighted at Booths 1706 and 1708.

The series features 82-key keyboards and provides an extended Teletype 33ASR format with a numeric pad which is said to accomplish rapid numeric entry regardless of mode of operation.

Standard features of the Model C 1400 include solid-state keyswitches, two-key rollover, 18 coded function keys and tactile feedback keys, the company said.

Keytronic can be reached at Building 14, Spokane Industrial Park, Spokane, Wash. 99216.

The advertisement was not illustrated, and no further details seem to be available. No elaboration is given as to what “tactile” meant here. Conceivably the multi-gang modules could have used the same buckling rubber sleeve system as the later discrete modules.

By 1977, Key Tronic had introduced single-unit plate-mount plunger modules, which would later be reduced in height to attain DIN compliance. In the 1977/78 Electronic Design Gold Book, Key Tronic referred to the plate-mounted type as “low profile solid-state keyboard”, and the older type as “standard solid state keyboard”. These plate-mount switches can be seen in the datasheet for Model L1696 from 1979, on the keyboards page. the older ganged (“standard”) type were still in production in 1981, based on example data.

Key Tronic’s foam pad capacitive keyboards came in tactile and linear options. The linear types were not truly linear due to the extra force introduced by compressing the overtravel pad (the foam pad). The tactile types used a buckling rubber sleeve.

The Model L1696 keyboard datasheet gives the following specifications for the tall discrete capacitive switches:

Total travel 0.171″ (4.34 mm) nominal
Key force 2.5 oz (70.88 g) nominal
Keyswitch reliability Minimum 100 million mean cycles before failure

The alternate action design used with the plate-mounted type is very similar to that of RAFI RS 74 and RS 76, with a tiny spring-loaded pin that follows a track within a sideways-moving slide block. In the RAFI design, the slide block runs in a slot provided by a tightly-fitting plastic insert. Key Tronic’s design uses an external piece for the slide block track, that is in turn retained using a plastic retainer that is placed around the switch. This arrangement can be seen in the Apple Lisa keyboard; Deskthority forum topic Pin spring for latching (CapsLock) Keytronic Foam & Foil depicts such a switch after its spring was lost.


Key Tronic’s Butterfly™ switch was advertised in April 1981 as being their first capacitive keyboard with linear feel. A former Key Tronic employee has stated that the Butterfly switch never entered production; he was not able to provide any further information, but he has been able to verify that the switch depicted in US patent 4209819 “Capacitive keyswitch” is the “Butterfly” type, with the late Ewald E. “Sig” Seignemartin (1929–2012) as principal inventor. It seems that Key Tronic intended to break away from the foam pad technique, but ultimately they chose to continue with foam pad and drop the “Butterfly” idea. The “Butterfly” name appears to refer of the shape and motion of the flexible capacitive plate inside the switch.

Screened contact

Key Tronic advertised “screened contact” keyboards as early as 1983. These units have no electronics and simply expose the key matrix on a flexible tail. Curiously, they are advertised to use “no silver traces or gold contacts”, which raises the question of what conductive material is used on the membrane sheets, as membrane keyboards typically use silver–carbon ink. The design of switch is not depicted, but the assembly uses plate-mounted modules of some kind, as the unused positions have the standard fillers fitted.

The Gavilan SC keyboard (1983–1985) uses a membrane assembly inscribed “SCREEN CONTACT”. The plunger modules are the same general design as the capacitive switches but are dual spring over membrane using a plastic piece to apply pressure to the membranes. The design is covered by Japanese patent S59-209225 (published 1984-11-27), with priority to a US patent application that seems to have never been granted. This keyboard type appears to include alternate action switches.



Patent Title Filed Published Product
US 3667787 Key top mount 1970-12-14 1972-06-06 Combined stepped/sloped keycap mount
US 4209819 Capacitive keyswitch 1978-03-13 1980-06-24 The “Butterfly” type that never entered production
US 4277780 Scan-controlled keyboard 1980-02-15 1981-07-07 Standard Key Tronic plate-mounted capacitive keyboard
US 5298706 Membrane computer keyboard and improved key structure 1992-08-13 1994-03-29 Applicable to the IBM TrackWrite keyboard

Notable products

IBM TrackWrite

Key Tronic were chosen by IBM to supply the TrackWrite keyboard for the ThinkPad 701 series of laptop computers. The TrackWrite keyboard is universally referred to as the “Butterfly” keyboard. This keyboard uses a switch type patented by Key Tronic (US patent 5298706, filed in August 1992) that does not involve a scissor mechanism or similar; instead, it’s a buckling rubber sleeve arrangement with a tiny guide shaft placed in the centre for the keycap. Photographs of a switch can be seen within 神話 The Butterfly – keyboard research but the design cannot be seen clearly enough to determine whether it matches the patent or not.


All material was scanned by Bitsavers unless otherwise noted.