[GreenKeys] Interfacing with the teletype...for newbies [M26 newbie, part 2]

[Duncan Brown]

Jomar,

Any AFSK converter (aka "Terminal Unit") made for amateur radio will 
work, eg. HAL, Dovetron, Flesher, etc and most will include the loop 
supply. (Older tube type and military units may only do 850 Hz shift; 
ITTY is 170 Hz shift.)

You can build a simple AFSK demodulator with a 2211 chip and an 
optocoupler interface - schematic enclosed.

Loop supply just needs 100-150 VDC source that can supply 60ma; plus a 
current limiting resistor. No regulation is required. Often old teletype 
supplies can be found, but they may contain selenium rectifiers which 
should be replaced with silicon rectifiers. (Selenium can put off 
poisonous gas when abused)

Good luck & Have fun,

Duncan
K2OEQ

On 6/30/2024 10:05 PM, Jomar Quilatan wrote:
> Hi all,
>
> So after a partial restoration of my model 26 (mostly cleaning and 
> de-gunking), I've been able to get it to at least code keyboard inputs 
> correctly (after giving it a moment to warm up...still will gradually 
> free up all the related parts) and fixed a carriage return issue 
> simply by increasing tension (thanks to a fellow person on this forum 
> for suggesting that fix).
>
> Now I'm on to the next part - getting stuff to be sent to my unit.
>
> Is there a rudimentary assembly that can be put together or bought to 
> interface external text sources, ITTY, etc with the Teletype (similar 
> to my temporary workaround of a 9V battery as my loop current), or is 
> this where having amateur radio gear / knowledge will come in (aka the 
> sky's the limit)?  In other words, what could be the next natural step 
> to take with this machine?
>
> Looking forward to your input.
> Regards,
>
> *Jomar (Joshua Martin) Quilatan*
> Mississauga (Toronto), Canada
> RA 0-8045
>
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