deskthority

I recently picked up an ITT Courier keyboard that was used with the ITT Courier 1700 terminal, a competitor for the IBM 3178 in the early mid 80's. The keyboard is quite beefy at over 3 kg. It has cast upper and lower case halves. The switches are the interesting part. I am not familiar with them and was hoping someone could identify them. There is a Micro Switch sticker on the plate. The switches are very short and appear to sit on top of a single membrane, sandwiched between two plates. They are very tactile and make a metallic click very similar to one of those dog training clickers, giving me the impression they it may be some sort of metal dome or leaf. I hate to make this comparison, but they feel closest to buckling spring of any switches I have tried and they even sound a little similar in that they ring.

Here are the pics:

That's basically a honeywell rubber dome. Neat layout though. A bit odd that it 'clicks', I suppose

Need to see the insides. Rubber domes can be many things, but not clicky!

Inside will be tough.It doesn't look like it was made to be disassembled. From what I can see the front and rear plates are crimped together. I need to twist each of the metal tabs that protrude from the front plate to align with the angled slot in the rear plate before I can separate them. If I do, I'm not sure I could ever get it back together properly. I will post a video with audio later. Its definitely not a rubber dome.

Actually, those tabs sound like a good system for the inquisitive. Much better than a Model M's shitty plastic rivets! Be careful and you should be good opening it up and closing it again.

I can certainly experiment with a tab or two. Worst case, I could remove all the tabs and bolt it back together like a model M bolt mod.

Well, in general, I'd pull the whole back plate off (with the board safely held face down, with caps removed) instead of trying to peek in at an angle for long. You won't get informative pictures, and the flexing can cause trouble. But sure, be slow and careful with the tabs. No need to commit to pulling it open unless you're comfortable with those.

Have you ever opened a Model F? They're a similar idea. Less tabs, but lots of springs within!

http://deskthority.net/workshop-f7/bm-a ... t9488.html

Be sure to understand the stabilisers before opening the board up. The AT's spacebar is its evil trick. I expect traps like that with other boards now.

Yes I have rebuilt several Model F's so I am comfortable with such things, but thanks for the reminder on the stabs!

Very nice keyboard BTW. I don't think I've ever seen this model before. So we still don't know if its a dome or not. To be or not to be...I'm not sure if we have any ITT keyboards in our wiki.

seebart wrote: ↑Very nice keyboard BTW. I don't think I've ever seen this model before. So we still don't know if its a dome or not. To be or not to be...I'm not sure if we have any ITT keyboards in our wiki.

We will shortly

Cool, thanks. I love these old keyboards.

Interesting layout - looks like an IBM 3278 with the PF keys on top, instead of to the right.

Here is a short clip with the sound.

Wow, sort of a heavy and very loud click! I could imagine now that you said they are similar to buckling springs.

Actually, I think this sounds a bit closer to Beamspring. Which would be appropriate! Clickiest "domes" I ever heard. There's something very mechanical going on in there.

Take it apart! Do eeeeet! We must know!

It will be taken apart tomorrow...sorry, my elderly mom trumps my keyboard addiction tonight.

It turned out to be very easy to take apart. The tabs were very easy to bend and it appears it should go back together without great difficulty either. What did I find? Look for yourselves. Note the small studs next to the tabs. These set the distance between the two plates, which will be helpful when I reassemble things.

So it seems its a thin metal diaphragm spring. The diaphragm is attached to the switch housing with melted plastic rivets much like the plate on the model M, unfortunately. Above the diaphragm is coil spring (copper in appearance). When the plunger is pushed, the spring compresses a short distance before the metal diaphragm buckles, after which the plunger and spring continue to compress. Travel is limited by a plastic tab on the plunger that rides in a slot in the switch housing, which can be seen to the right of center below.
The membrane is two layers, but I was unable to easily separate them. It as if there is an adhesive holding them together and I didn't want to damage it. They membrane layers are very thick compared to those of a model M. They are thick enough that when held at one end they do not bend. Here is a video of the switch actuation.

Engicoder: Great work for the disassembled and the details.
I saw the another keyboard with that switch on auction few months ago. And wondering it worth to buy.
Is that a nice switch? Should I buy it?
thanks

p.s. I found the another IBM logo keyboard with this blue switch on geehack.
https://geekhack.org/index.php?topic=7377.0

Very nice work Engicoder. Always great to see a "new" switch being found and demonstrated. I'd like to add it to the wiki if you don't mind unless you want to do so yourself. The thin metal diaphragm spring is very low in profile much like Fujitsu Leaf Spring second generation but this mechanism is different of course.

@terrycherry; lowpoly had that IBM unsaver for sale. Whoever got that got a mighty bargain at €20 since we now know it's not RD. I should have bought it.

http://deskthority.net/f-o-r-s-a-l-e-f5 ... it=lowpoly

Sure thing, have at it. I will work on getting the keyboard itself added. If I might suggest classifying it as "metal diaphragm spring over membrane". I am going to disassemble one switch to get a few photos of the spring. I will add them later.

That IBM unsaver is most definitely a rubber dome, which is why I assumed that this would be too. It just looks like there was an earlier version of this switch, perhaps before microswitch was gobbled up by honeywell, that looks quite similar except isn't rubber dome. So, quite a neat discovery!

Parak wrote: ↑That IBM unsaver is most definitely a rubber dome, which is why I assumed that this would be too. It just looks like there was an earlier version of this switch, perhaps before microswitch was gobbled up by honeywell, that looks quite similar except isn't rubber dome. So, quite a neat discovery!

Actually, Honeywell bought Micro Switch in 1950.

Hmm... interesting... one wonders why it persisted as a separate brand, then.

Awesome stuff mate, thanks for sharing! That's definitely clicky indeed. In what way is this that different from beam spring? I'm not sure I see the difference.

Chyros wrote: ↑Awesome stuff mate, thanks for sharing! That's definitely clicky indeed. In what way is this that different from beam spring? I'm not sure I see the difference.

They are very similar in that both apply pressure to a spring steel "beam" until it buckles which results in a key stroke being registered. They differ in how the keystroke is registered/detected. The beam spring switch has a flyplate attached to the ends of the beam so that when the "beam" buckles and the ends turn up, it lifts the flyplate away from the pcb and changes the capacitance. This change in capacitance is detected by the controller as a key stroke. The ITT (Micro Switch) "beam" buckles and the dimple on the center section applies pressure to a pair of membranes which completes a circuit. The other slight difference is that with the ITT, the coil spring provides resistance and also acts directly on the spring steel "beam", while with the beam spring, the spring only provides resistance while a rigid plunger acts on the "beam".

I see, cheers . Does it feel robust as a mechanism?

Chyros wrote: ↑I see, cheers . Does it feel robust as a mechanism?

It seems robust from a durability standpoint, The plastic of the switch housing is quite thick compared with modern switches; in fact everything piece of this keyboard is thicker/stronger than modern equivalents. As far as feel, the travel is fairly smooth and the tactile bump is very crisp. The fault with the full assembled keyboard, as it is today, lies in consistency. There is slight variance in feel and sound between the switches. The tactile bump of some keys is more noticeable than others. The switch clicks on both downstroke and upstroke. Some ring more than others. By ring, I mean the reverberation after releasing the key that is characteristic of the buckling spring keyboards. I suspect these inconsistencies may be due to variations in pressure between the two plates.

I found the interesting stuffs about ITT tech logo with keyboard product as following:
ITT 2020 for Apple II at 1979



Robotron K7673


ITT 88200-01 AT Keyboard

Huh, I'd never heard of the ITT 2020 until now. It was an Apple II clone. But a licensed clone! Apple let them have at Europe with their fancy PAL video…

https://en.wikipedia.org/wiki/ITT_2020