[GreenKeys] Slightly OT - Churchill War Room

[Richard Knoppow]

    Two things occur to me, one is a book called "Visible Speech" 
by Ralph K. Potter about work done at Bell Labs to analyze speech 
and the other is a devise used by AT&T on its transatlantic radio 
circuits called a "shuffler". The shuffler broke up the speech 
spectrum into several parts which were frequency shifted and 
transmitted some with and some without inversion, the pattern 
changing ever few seconds to provide privacy. I don't know when 
this was put into practical use but I remember hearing it being 
used on AT&T short wave circuits. One could recognize the pattern 
of speech but not the words. RCA used simple inversion of 
independent sideband transmission, easy to hear in the clear with 
a decent receiver.  Neither of these may have anything to do with 
the described encryption
_Visible Speech_ Ralph K. Potter, George A. Kopp, Harriet C. 
Green (1947) New York D. Van Nostrand Co., Inc.


On 3/30/2019 6:37 PM, Duncan Brown wrote:
> Good info on SIGSALLY at Jerry Proc's site: 
> http://jproc.ca/crypto/sigsaly1.html
> 
> Duncan
> K2OEQ


-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL