TheCodeBreakers
drawl then entered a special locked room, barred to all except
government-licensed employees, where the A-3 equipment mangled it.
Here engineers watched dials and listened to the sound to make sure
that the speech was properly scrambled. At the transmitter, channel
mixers continually shifted the transmission from one frequency to
another, so that anyone listening on one circuit would hear it go
suddenly blank.
And someone was indeed listening. The Deutsche Reichspost—which,
like other European post offices, handled telephone and telegraph traffic
as well as mail—-realized that the only telephone link between England
and the United States was the radio circuit, and it reported "The special
national political importance of this communication connection has
caused the D.R.P. to try with all available scientific means to decipher
the conversation carried on this connection." A task force under Postal
Counselor Graduate Engineer Vetterlein of the D.R.P.'s
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