TheCodeBreakers
For example, a
factor of 1,000 might be added to all frequencies in the 300-to-3,300
band, so that a tone of 500 c.p.s. would be
*It does not seem possible to devise a scrambler that distorts the
sound itself (i.e., the vibrations in the air) because, once the waves were
degraded by, say, some kind of baffle, they could not be restored to their
original form. Transposition systems, on the other hand, might be
possible in a very crude form by means of mechanical phonographs.
From a practical point of view, however, nonelectrical scramblers may be
ruled out. None ever seems to have been constructed.
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shifted to 1,500. One of 2,800 c.p.s. would then be enciphered to 800.
Band-splitting splits the frequency band into several smaller bands
and interchanges these. Filters can divide a 250-to-3,000 band into five
subbands of 550 cycles each: subband A of 250 to 800, subband B of 800
annaabi.ee 
