[GreenKeys] Navy Teletype Message Generator

[Alf Fisher]

On 24/01/2023 15:55, Gillian Webb wrote:
> Nifty! I found the original plans this appears to be built from, or at 
> least a very similar "solid state fox box" circuit, on page 30 of the 
> November 20, 1976 issue of Ham Radio Magazine:
>
> https://archive.org/download/hamradiomag/ham_radio_magazine/Ham%20Radio%20Magazine%201976/11%20November%201976.pdf
>
> What's the info printed on that white chip? I agree it looks like they 
> "adapted" something in - thinking a comparison to this reference 
> design could shed light on this.
>
> Cheers,
> Gillian
>

I was wondering if anyone had actually built this fox box from the 
article in HR Nov 76?
I've discovered a feature of the design that is not sensible.
Looking at Fig 3 in the article, the power to the collector of output 
transistor of the opto coupler Q6 is derived from the loop current but 
only when the loop is open.
When the run/stop switch stops all the counters from running, there will 
be no power to keep the loop transistor Q5 on, so the loop will go open 
- and...
Maybe I'm missing something but has anyone got a work around for this 
problem?

73,
Alf G3WSD