[liberationtech] Efficient digital one-way communication

[Don Marti]

begin Jens Christian Hillerup quotation of Mon, Mar 04, 2013 at 06:53:05PM +0100:

> Whoops, we're drifting off-list. I've included the relevant parts (and
> committed a stereo fix to the main repo that fixes the bug from my
> second mail).

DTMF uses two pitches at a time - 
  http://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling

Chords might be a way to get more information in.

(I can imagine putting an old cassette boombox up
in a tree, with enough blank tape before the music
starts to get away.  Would anyone record it and try
to decode?)

-- 
Don Marti                      +1-510-332-1587 (mobile)
http://zgp.org/~dmarti/        Alameda, California, USA
dmarti at zgp.org