In the 090404 MMD Steve Bentley wrote:

    "A U.S. patent was granted in June 1942 to Antheil and Hedy [La-
    marr] for an early version of "frequency hopping," using a piano
    roll to change between 88 frequencies.  This was intended to make
    radio-guided torpedoes harder for enemies to detect or jam."

Mostly true.  That patent was held secret until well after it expired
and is a relatively easy to understand basis for spread-spectrum radio
technology used today by portable phones, wireless routers, blue-tooth
devices, etc.  The patent illustrates and explains how an eight "note"
roll can be used, but does mention 88-note piano rolls as an example of
similar existing technology.  Notwithstanding the com- ments in Wiki-
pedia's article about prior patents, Antheil and Lamarr's patent is the
first to my knowledge to utilize the rapid shifting of the transmission
frequency in a secret fashion and includes such enhanced features as
fake messages on frequencies the real receiver will ignore.  The refer-
enced patents mentioned on Wiki discuss methods of mixing a known
disturbing noise-type signal with the audio and later subtracting that
at the receiver end to derive the original audio.  This is not in the
same class as the secure transmission method in Hedy's patent.

To my knowledge radio guiding has never been used in torpedo systems.
Modern torpedoes are wire-guided.  It was simply an idea that Hedy
wanted to give to the American Navy, which they rejected.  I suspect
submarine commanders would have been reluctant to send any RF signal
that would locate them on an enemy RDF receiver and at the same time
give notice to the enemy that they are a target.  I'm told the patent
application was cleaned up by an electrical engineer at MIT before
submission.

Apparently Hedy's first husband was an important arms merchant who sold
to many international buyers including Hitler's Germany.  There are
stories that he used to ask her to sit in on discussions with business-
men.  Perhaps that was his way of disarming them, as she is reported to
have been even more striking off screen than on.  She was apparently
competent in understanding their discussions and derived the method she
patented from some of them.

Don Shenbarger