🚀 go-pugleaf

 In <1993Jan3.110338.25314@qualcomm.com>
 karn@servo.qualcomm.com (Phil Karn) writes:

>In article <1993Jan3.054517.29505@colnet.cmhnet.org> res@colnet.cmhnet.org (Rob  Stampfli) writes:
>>>Another is that Bell Labs developed a truly remarkable (given the
>>>technology of the day) secure speech system that really was secure. It

>>How did they keep them in sync?

>Good question. I seem to remember that this was a problem. The system
>was written up in IEEE Spectrum some years ago, but I don't have a
>copy on hand.

 Kahn, D.  1984.  Cryptology and the origins of spread spectrum.
 IEEE Spectrum.  September.  70-80.  (Also see letters in December.
 10-14.)

    "Both ends agreed when they would start the records.  The agreed-
 upon timing signal from the U.S. naval observatory's radio station
 WWV, which broadcast time signals, caused the turntables to begin
 revolving.  An ingenious clutch ensured that they accelerated so
 smoothly that the stylus did not jump out of the groove.  The
 records, a U-boat-infested ocean apart, would be within half a
 second or so of synchronization.  Chirps filled Smith's telephone.
 Then, watching a counter calibrated in milliseconds, the sergeant
 used a phase shifter to advance or retard turntable speed and bring
 the two units into exact synchronization.  As they came into sync,
 the peeps faded into silence."


>I believe it was the same issue that explained how Hedy Lamarr (yes,
>the movie actress) invented frequency hopping, one of the fundamental
>forms of spread spectrum radio.

 Screen star devises a frequency-hopping scheme.  (sidebar, p. 78)

 Secret Communication System.  H. K. [Hedy] Markey, et. al.
 U.S. Patent 2,292,387, issued Aug. 11, 1942.

 Basically seems to use piano-type-rolls with slots.  Apparently the
 slots allow electrical contact with various capacitors which affect
 a variable-frequency oscillator (VFO) to produce different (radio)
 frequencies at different times.  Identical rolls produce the same
 frequency-hopping sequence.

 ---
 Terry Ritter   ritter@cactus.org