[RTTY] FW: Slightly off topic, history of 850 Hz shift?

[Michael Keane K1MK]

If I recall correctly, the frequencies of the standard audio tones 
were taken from the Western Electric/Bell standards developed for 
multiplex landline teletype which predated radio-teletype by years.

73,
Mike K1MK

At 12:13 PM 9/28/06, Jan Palmquist wrote:
>The old 850 Hz shift used 2121 and 2975 as
>frequencies.
>
>2125 is fifth harmonics of 425 Hz
>and 2975 is the seventh harmonics.
>
>So you can use a standard 425 Hz tuning fork
>as tuning aid.
>
>73 de Jan - SM5FUG
>
>
> > The following is posting for Chris, N3JLY, who is not on the 
> RTTY-Contesting
> > reflector. If you respond, please copy Chris Smolinski
> > <csmolinski at blackcatsystems.com>
> >
> > Dick AA5VU
> >
> > ------ Forwarded Message
> > From: Chris Smolinski <csmolinski at blackcatsystems.com>
> > Date: Thu, 28 Sep 2006 11:29:19 -0400
> >
> > Hi Dick,
> >
> > Sure, please go ahead and post it, thanks!  I'm sure someone out
> > there knows the history. I am curious if the shifts commonly used are
> > based on some engineering/technical reasons, or if they were
> > arbitrarily chosen.
> >
> >> On 9/28/06 8:45 AM, "Chris Smolinski" <csmolinski at blackcatsystems.com>
> >> wrote:
> >>
> >>>  Someone asked me why much of the military RTTY on HF commonly uses
> >>>  850 Hz shift. I am curious if anyone knows the history behind the
> >>>  selection of this shift rate, or if it was just arbitrary.
> >>>
> > ------ End of Forwarded Message
> >
> >
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Michael Keane K1MK
k1mk at alum.mit.edu