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Jelco Co., Ltd. (株式会社ジェルコ, also written with “エ” as 株式会社ジエルコ — Kabushiki Gaisha Jeruko) was a Japanese keyboard manufacturer. Very little is known about Jelco switches, and there is little trace left of the company itself. Hopefully with time, more will be discovered. Although a number of their patents are available online, there is little correspondence with the known and suspected switch types.


Details on Jelco keyboards and switches are obscure. A number of brief details were advertised in JEE (Journal of Electronic Engineering) which are made partially accessible through Google Books.


JKS-2 (JKS-20)

JKS-2, also known as JKS-20, is an unclear switch type. The Google Books scan appears to show quite stout terminals in a manner similar to the Mitsumi shift lock keyswitch in early Commodore 64 keyboards. JKS-2 appears to be designated “micro-computer use”. The advertised specifications in 1980 were:

Operating force 60±20 g
Total travel 4+0.5 mm
Rated lifetime 10 million cycles minimum
Contact resistance Under 100 Ω

The switches were listed solely as “JKS-2” in the 1980 advertisement. A 1980 advertisement calls them “JKS 2 (JKS-20)” with no further clarification. This is the only observed instance of a two-digit number as seen with JKS-91.


JKS-5 is momentary switch type designated “for printer”, where the “printer” illustration shows the keyboard from a desktop calculator. The corresponding alternate action type is KRS-6. Confusingly, the specifications for these switches call them “SKS-5”, and are as follows:

Operating force 60±20 g
Total travel 4 mm
Rated lifetime 2 million cycles minimum
Contact resistance Under 100 Ω

These switches, shown in the same 1980 advertisement as JKS-2, look like fairly typical switches for the era, but presumably with an internal contact arrangement only suitable for light use.


JKS-91 is only known from the Australian Microbee 1980s home computer. The part or model number was provided by Australian manufacturer Microbee Technology. No official literature of any form has been forthcoming, not even an invoice with part numbers on.

These are elastic contact switches, with the dome placed vertically at the side of the switch.


A switch was found in the “TOuSJE” keyboard, with characteristics very similar to JKS-91. In particular, it has a vertical contact module with a horizontally-protruding rubber dome. The external design of this contact module bears a significant resemblance to that of Omron B3G-S. This keyboard, PCB model JMC-100B, was made by Datacomp. Most switches in this keyboard were SMK J-M0404 series, with no apparent reason for a few being of another brand.

A very similar keyboard, PCB model JMC-82 and Datacomp model DFK-505, was found with solely these switches; this keyboard was sold by Phoinix. Here, you can see that the contact system is something like Futaba MD series, but with a rubber dome to transfer the force from the plunger instead of a metal spring. Overall, the design seems to be a hybrid of Futaba, Omron and Alps switches.

These switches are not identified at all, and are not branded, but they seem to also be Jelco.

Note that both keyboards have the same number of keys, so the JMC codes do not indicate key count.

Membrane types

Photos of the TRS-80 Color Computer keyboard show a membrane switch type that matches US patent 4631378. The folded outer membrane sheet (with the circuit pathways and contact pads) is labelled “JFK-8002-04A”, where “JFK” is also a known prefix to some Jelco keyboard series. This example seems to date to 1984 according to the IC dates within the computer.

Keyboard STM PPC002 uses a more conventional plunger-over-dome arrangement. Here, the membrane code is “JFK-8001-03”, and the membrane circuitry design matches that of the TRS-80 Color Computer membranes. This example also appears to be from 1984 according to the IC dates.

A third type was used in the Coleco ADAM Keyboard. Here, access to the complete set of photos is blocked, but the “JFK-” prefix on the outer membrane sheet is visible, as is the characteristic membrane contact position design. Via YouTube video TOTC-02.03: Coleco Adam Keyboard Repair (membrane), the membrane code is confirmed to be “JFK-4004-03”, as seen in another ADAM keyboard that appears to have been made in 1983 (昭和58) based on the production label. The keycap mount of this type is reminiscent of JKS-91, and moreover the design directly corresponds with Jelco utility model 昭和60-075928 (U1).


Jelco placed a full-page advertisement in JEE in 1982, entitled “JELCO, Japan’s Leading Keyboard Specialist”. Portions of this can be seen on Google Books. Although the entire page cannot be viewed, the accessible fragments of material appear to demonstrate that the advertisement is fairly vague and unhelpful. The advertisement does however give us four series names: JFK-3000, JFK-4000, JFK-5000 and JFK-6000. It is conceivable that these series name match up with the numbering found on the membrane sheets.

JFK-3000 Series

JFK-3000 was advertised as in JEE in 1982 as follows:

JELCO’s JFK 3000 series low-profile full-keyboard switches were developed to meet the rising needs of design engineers for compact and lightweight switches. The JFK-3000 series full keyboards are only 15 mm in height, including the keytops, thus reducing the overall height to just half that of conventional keyboards.

No other details were given. The keyboard is depicted as plate mounted, but may be a membrane type considering the dimensions.

JFK-4000 Series

JFK-4000 was advertised as in JEE in 1982 as follows:

The JFK-4000 keyboard units are designed to be simple as well as highly reliable and economical. These keyboard units consist of individual FKS-100 and FKS-200 keys in response to customers’ requirements. JFK-4000 keyboards are excellent choices for date entry systems, word processors, electronic typewriters, etc.

There is no known indication of what “FKS-100” and “FKS-200” are, and the description of “individual [keys]” does not seem to tie in with the non-modular design of the Coleco ADAM keyboard that has a “JFK-4004-03” membrane code. Of course, the term “individual” could be in contrast to membrane surface and rubber mat keyboards such as those used in the Sinclair ZX80, ZX81 and ZX Spectrum. The Jelco advertisement is simply too vague, and the illustrations merely show fully-assembled keyboard modules without any depiction of the switches.

JFK-5000 Series

JFK-5000 was advertised as in JEE in 1982 as follows:

JELCO’s JFK-5000 series keyboards are unique full keyboards offering a high level of performance at very reasonable prices. Their low-profile and lightweight design allow compact overall design, and from 53 to 64, keys can be freely selected.

JFK-6000 Series

JFK-6000 was advertised as in JEE in 1982 as follows:

JELCO’s JFK-6000 series full keyboards are comprised of modular key switches JKS 2 (JKS-20) so as to meet the particular needs of each customer. Up to 67 keys can be freely selected.

Again, no further details are given.


“Jelco Type PR-5701” is mentioned in Byte magazine, volume 8, 1983, in a letter to the magazine.

Patents and utility models

Company Patent Title Filed Published Notes
株式会社ジェルコ JP 昭和56-84238 (U1) 押釦スイッチ (pushbutton switch) 1979-12-03 1981-07-07 Dual spring over membrane with plastic membrane spring
株式会社ジェルコ JP 昭和59-55703 (U1) 光ファイバスイッチ (optical fibre switch) 1982-10-04 1984-04-12 Diagrams unclear
株式会社ジェルコ JP 昭和59-58848 (U1) キーボード (keyboard) 1982-10-04 1984-04-17 Diagrams unclear
株式会社ジェルコ JP 昭和59-161228 (U1) 押釦スイッチ (pushbutton switch) 1983-04-15 1984-10-29 Modular spring-over-membrane with the same force curve shape as Tokai MM9
株式会社ジェルコ JP 昭和59-165622 (U1) 押釦スイッチ (pushbutton switch) 1983-04-21 1984-11-06 Dual spring over membrane with plastic membrane spring
株式会社ジェルコ JP 昭和60-075928 (U1) 押しボタンスイッチ (pushbutton switch) 1983-10-31 1985-05-28 Plunger over dome over membrane; corresponds with the Coleco ADAM keyboard
株式会社ジェルコ JP 昭和60-75929 (U1) 押しボタンスイッチ (pushbutton switch) 1983-10-31 1985-05-28 Spring over membrane with pressure actuator; corresponds with the TRS-80 Color Computer keyboard
Jelco Co., Ltd. US 4631378A Push button switch 1984-10-19 1986-12-23 Combines 昭和59-165622 (U1) and 昭和60-75929 (U1)
株式会社ジェルコ JP 昭和61-145437 (U1) 押しボタンスイッチ (pushbutton switch) 1985-02-28 1986-09-08 Spring over membrane
Jelco Co., Ltd. US 4831223A Push-button switch 1987-03-25 1989-05-16 Corresponds to 昭和61-145437 (U1)
株式会社ジェルコ JP 平3-038088 (A) フレキシブル印刷配線板における電子部品の接続固定方法 (connecting components to FPCs) 1989-07-05 1991-02-19 N-key rollover diode on membrane?