[GreenKeys] Tone frequency history?

[Harold Hallikainen]

On Fri, October 8, 2021 4:41 am, Nick England wrote:
> AN/FGC-1 block diagram and general description is on this page
> https://www.navy-radio.com/rtty-demod.htm
>
> I think I have the manual somewhere and will scan it when I get a chance.
>
> Nick

Thanks! I suspect this is the origin of the tones for amateur radio work.
See paragraph b at
https://www.navy-radio.com/rtty/ww2/FGC1-TM11356-abstract.pdf#page=5 .



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