ITT ETL18 Horizontal Spring key switch

[snuci]

I found a rather unique key switch in a recent vintage computer acquisition. This is an ITT ETL18 key switch that is in a rare Interact One computer. This particular model is a later model than the normal Interact One which normally features a chicklet keyboard. This model has these ITT ETL18 key switches that were made in West Germany from early 1980. I'll cover the computer in another post when I can take proper pictures but these key switches are pretty awesome and appear to be a completely different class of key switch.

These switches feature a horizontal internal spring that makes the key feel and force act like a beamspring key switch. When the key stem is pressed, the internal spring bows; giving way to almost no pressure on the down press. On release, the key stem almost snaps back in place. It is not a clicky key switch but it very tactile.

I've experimented with a different size spring to see if I can adjust the key weight as they are slightly heavy but wasn't able to find a spring that would match properly. An IBM buckling spring is too short as it fits inside of the key switch but doesn't "bow" as much as the longer spring that is already in place. I think that if the existing spring was slightly shortened, it would feel like a lighter weight. A slightly longer spring would make the key weight feel heavier as more force is needed to bow the internal spring.

In an case, here are some selected pics from my Wiki post here: wiki/ITT_ETL18

Interact One computer

Interact One.JPG (118.03 KiB) Viewed 1863 times

[HaaTa]

Neat!

[snuci]

Thanks Haata.

More computer pics here: photos-f62/interact-model-one-computer-t15081.html

[webwit]

Wow, what a weird switch. Does it feel good?

[seebart]

I saw that on the wiki...unusual design to say the least. Very tactice eh? Seems ITT came up with good stuff.

[snuci]

Wow, what a weird switch. Does it feel good?

I am a terrible judge of switch feel but it does feel but Daniel Beardsmore did manage to find a sample and he said it was very smooth. I actually tried an IBM Model M spring in it to replace the existing internal spring but it was not long enough to have the key stem travel very much. I do believe that the length of the spring will make it stiffer (longer spring) or softer (shorter spring) but the length of the existing spring is pretty good. It's a solid switch.

It's interesting in that there is a channel for the spring internally that is bowed so you can't put the spring in without poking it in with s thin tool and slamming the top shut while slowly pulling out the tool.