YUAN, T.; YUAN, Tong. (BrasilCentro de Tecnologia e Recursos Naturais - CTRNPÓS-GRADUAÇÃO EM ENGENHARIA CIVIL E AMBIENTALUFCGUniversidade Federal de Campina Grande, 1973-03)
In this work four types of speech scrambler are studied: by inversion of spectrum, by division of spectrum, by frequency sampling and digital. For each case its advantages and disadvantages are analyzed.