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A band scrambler which processes only time domain samples is described. The band scrambler has the effect of dividing the input signal spectrum into N sub-bands. The N sub-bands are permuted such that the r th band is mapped onto the k.r th band modulo N, where N is a constant of the scrambler and k

A band scrambler which processes only time domain samples is described. The band scrambler has the effect of dividing the input signal spectrum into N sub-bands. The N sub-bands are permuted such that the r th band is mapped onto the k.r th band modulo N, where N is a constant of the scrambler and k is the key which is variable in the range 2

대표청구항 ▼

A speech scrambler, including an analogue-to-digital converter having an input for an input speech signal and an output, and which is operative to produce a series of time samples x(n) at said output, means having an input and an output, said input being operatively connected to said output of said

A speech scrambler, including an analogue-to-digital converter having an input for an input speech signal and an output, and which is operative to produce a series of time samples x(n) at said output, means having an input and an output, said input being operatively connected to said output of said converter to derive a further series y(n) of time samples at said output from the x(n) in accordance with the following equation: [Figure] where h(n′) is a windowing function, and [Figure] N is a constant of the system, k is a key selected from the range 2≤k≤N-1 and k and N are coprime, and digital-to-analogue converting means having an input connected to said output of said deriving means and an output and which is operative to convert said further series of samples y(n) into a scrambled output signal at said output.