Scrambler Phones
The first scrambler phones were invented prior to the Second World War to secure voice transmission for commercial use. You can think of a scrambler as an encryption device for analogue signals – an analogue signal is a continuously varying, smooth signal, whilst a digital signal has discrete values.
Standard digital encryption works by applying mathematical functions to the digital data to produce codes. Scrambling works by taking an analogue waveform and modifying the frequencies in a way that makes it incomprehensible. The wave is then unscrambled, a process that transforms the wave back to its original form.
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