
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<k<N-1. The output samples y(n) produced by the scrambler from the input speech signal samples x(n) are defined by the equation: ##EQU1## The down-sam...











