Voice privacy system

Claim 1

A voice privacy system comprising: a first fixed frequency signal source associated with each speech frequency sub-band of a plurality of speech frequency sub-bands and operative at the center frequency of its associated speech frequency sub-band for producing first and second output signals in quadrature phase displacement; first and second balanced modulators connected in first and second signal channels, respectively, of each separate speech frequency sub-band to receive speech input signals and the first and second output signals, respectively, of each said first fixed frequency source, for producing corresponding lower frequency output signals in each said first and second signal channels; a lowpass filter of predetermined bandwidth connected in each said signal channel for filtering the output signals of said first and second balanced modulators in each signal channel; second fixed frequency sources, each operative at the center frequency of one of said speech frequency sub-bands for producing first and second output signals in quadrature phase displacement and being connected to the first and second signal channels of another of said speech frequency sub-bands; third and fourth balanced modulators connected in said first and second channels, respectively, of each said speech frequency sub-band to receive the filtered output signals of the lowpass filters in said first and second channels and the first and second output signals, respectively, of said second fixed frequency source, for producing output signals correspondingly disposed about a center frequency other than said first fixed frequency as determined by the frequency of each particular second fixed frequency source; means for summing the output signals of said third and fourth balanced modulators of each speech frequency sub-band; and means for summing the output signals of all said plurality of speech frequency sub-bands.