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Jelco switches

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, none of these correspond with the known and suspected switch types.


The only semi-confirmed type is JKS-91. The part number was provided by Australian manufacturer Microbee Technology who used them in their 1980s home computers. No official literature of any form has been forthcoming, not even an invoice with part numbers on.

These are “integrated dome” 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.


Company Patent Title Filed Published
Jelco Co., Ltd. US 4631378A Push button switch 1984-10-19 1986-12-23
Jelco Co., Ltd. US 4831223A Push-button switch 1987-03-25 1989-05-16

Additional patents exist in Japanese only.