[GreenKeys] Tri-tone RTTY

[Nick England]

I just came across an interesting tidbit - in WW2 the German Lorenz SZ42
encrypted 50 baud RTTY used three simultaneous tones each for mark and
space - providing diversity to overcome fading
*Mark* 900Hz, 1620Hz, 2340Hz
*Space* 540Hz, 1260Hz, 1980Hz

At the bottom of this page are some audio files to hear tri-tone and
regular RTTY,
https://lorenz.virtualcolossus.co.uk/technical.html

Nick K4NYW
Contributor, FWIW Dept.
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