Davall DTM-40 (1960's)


10 May 2019, 13:09

I recently got a Davall DTM-40 teaching machine which was made in England around the 1960's. There is practically no information about them however I found a few patents which explain their purpose but other than that, nothing. The thing weighs just over 3kg with the cable included. Considering it only has 21 keys, this is quite possibly the heaviest number pad I've seen...
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25-conductor wire (nearly 12mm diameter) with a HUGE 25 pin plug on the end, wow.

I thought the outside was impressive but I was pleasantly greeted with some logic boards once inside.
top off.jpg
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The patents stated that the keyboard would 'electronically lock' which is what I assume the right side board handles.
right logic.jpg
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Interestingly, the left logic board uses a PCB edge connector rather than being soldered. This was probably so that the board could be swapped.
left logic.jpg
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left logic removed bottom.jpg
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The keyboard is possibly the least interesting part of this. It uses Micro Switch magnetic reed switches and doubleshot purple keycaps. Pressing any key even slightly off-center results in binding. The larger caps are stabilized, but poorly so. I might prefer the feel of my Clare-Pendar reed switches.
switch markings.jpg
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keyboard matrix.jpg
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I'm tempted to trace the PCBs and see how the thing works but it's unlikely a Teensy will get it working. It would certainly be interesting to have it on the desk as a numpad - 'Davall unsaver' has a nice ring to it :D


06 Aug 2019, 13:30

Update: This will be slightly off topic but still relative to the keyboard in the original post. The same seller listed the actual terminal so I bought it. The thing weighs well over 15kg and is very big. I just thought I'd show some of the internals off:
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logic boards
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"Transmitter control mechanism" made by Teletype Co.
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I might disassemble it further and post some more photos. I have no clue what to do with it afterwards as I have no space to store/display it.

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06 Aug 2019, 14:11

Got a picture of the outside of the keyboard?

What makes you think this is 1960s rather than 1970s hardware? You could be right for all I know, but were those switches even made back then?

Edit: oh, they were! 1966
Last edited by Muirium on 06 Aug 2019, 14:32, edited 1 time in total.


06 Aug 2019, 14:29

Just look at that wiring loom man. All cut to length and neatly loomed together, spacing on the ties all the same.... you just dont get things made like that anymore. Someone took care and pride in there work.


06 Aug 2019, 15:21

It really is a beautiful sight. I think I appreciate tidy wiring like this because of how much effort went into it (and that I can't do it as good :lol: ) I actually would like to know the exact date of when it was made but sadly this is the only one I can find. I'll see if there are any date codes inside the machine later. I've checked patents and found 1 reference to the company (Davall Teaching Machines) which lead nowhere but mentioned mid-1960's.

I can't really figure out what it's meant to do. I'm guessing the tape is programmed with something on a Teletype, inserted into the terminal trainer which then displays something e.g. the lights come on then the student has to press the correct key?
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06 Aug 2019, 15:54

The way the inside looks screams mid to late 60s to me.

Oh and if you like old wire looms check out this video of a 1967 multi meter.

https://www.youtube.com/watch?v=4xrcBoe ... u.be&t=103

WOW . just WOW.


06 Aug 2019, 19:57

Incredible stuff! I want to do something like that inside a keyboard build but I doubt it'll ever be seen.

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