Secure Telephone Unit (STU)-III/Secure Telephone Equipment (STE)

Telephonic system and associated equipment using a ciphering engine to allow for encrypted transmission of voice and other audio and/or digital data over the public telephone network. Secure Telephone Unit (STU)-III/Secure Telephone Equipment (STE) operate by taking an audio signal and digitizing it into a serial data stream, usually 8,000 bits per second. This is then mixed with a “keying stream” of data created by an internal ciphering algorithm. This mixed data is then passed through an internal Codec to convert it back to audio so it can be passed over the telephonic system.