IIRC the scrambler I wrote for a marine radio application had 5 bands (which means each is about 600Hz wide for a 3kHz channel). The codes the user input would

IIRC the scrambler I wrote for a marine radio application had 5 bands (which means each is about 600Hz wide for a 3kHz channel). The codes the user input would select where each of the 5 bands were mapped to. I think we had 16 combinations and that was pushing it -- it is pretty amazing what you can do to voice and still have it be understandable.