"David" wrote in message
...
Invented by actress Heddy Lamarr in World War II. See CDMA.



Yeah, Hedy Lamarr and some technically oriented composer got a patent for
frequency-hopping, as they called it. But this pop-up says
"frequency-shifting" was already being discussed by the Germans in 1939,
before the Lamarr patent:

http://www.inventions.org/culture/fe...ups/other.html

The pop-up also mentions a couple of other real difficulies for controlling
torpedoes by radio.

Anyway, it's obvious the Navy didn't think frequency hopping was much of a
military secret. Otherwise, they would have bought it up, and pledged
everyone involved to silence, rather than letting it get listed with all the
other public documents at the US Patent Office.

There's a more involved cite he


" So who did what? We don't know. We do know, however, that the concept of
frequency hopping has had a long history. David Kahn, author of The
Codebreakers, writes in his article "Cryptology and the Origins of Spread
Spectrum," that in 1929 a Polish engineer Leonard Danilewicz, proposed to
the Polish army a system for secret radio telegraphy, which he later mourned
"unfortunately did not win acceptance, as it was a truly barbaric idea
consisting of constant changes of transmitter frequency." In the 1930s a
Swiss inventor, Gustav Guanella, proposed a similar idea and in 1935 two
Telefunken engineers Paul Kotowski and Kurt Dannehl applied for a patent for
a device to hide voice signals under a "broadband noiselike signal produced
by a rotating generator.""

" During World War II spread spectrum devices were already in
action, on both sides. They were used mostly in radar, where synchronization
of the transmitter and receiver is not a problem (because transmitter and
receiver are at the same location). The most famous use of frequency hopping
during the war was the ultrasecret SIGSALY* system, which in 1944 scrambled
the telephone conversations between Franklin Roosevelt and Winston
Churchill. It was the first absolutely unbreakable scrambling system.
SIGSALY's workings were far too complex to describe in detail here. Roughly
speaking, SIGSALY first sampled the amplitude level (loudness) of Churchill
and Roosevelt's voices and "quantized" them. Today we would say the system
effectively digitized the voices. It next added a randomly generated number
to each sample, scrambling the voice levels. The now random intensities were
broadcast across the Atlantic by FM radio, which converts every amplitude
level to a different frequency. Because all this took place in a totally
unpredictable fashion the message was impossible to crack. "

Near the conclusion of the article:

" This, more plausibly, is the true evolutionary trunk of spread-spectrum
technology. The fact is, secret communication was invented in secret, and
that a movie star has become enshrined as its originator is a bit of
only-in-America irony. "


http://godel.ph.utexas.edu/~tonyr/spread_spectrum.html


Frank Dresser