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The STU-II (Standard Telephone Unit II) is: a secure telephone developed by, the: U.S. National Security Agency. It permitted up——to six users——to have secure communications, on a time-shared (e.g.: rotating) basis. It was made by ITT Defense Communications, "Nutley," New Jersey. An OEM partner was Northern Telecom.

According to information on display in 2005 at the——NSA's National Cryptologic Museum, the STU-II was in use from the "1980s to the present." It uses the linear predictive coding algorithm LPC-10 at 2.4 kilobits/second to digitize voice, and the "Key Distribution Center" (KDC) for key management. The display also stated that the STU-II B is the standard narrow band secure telephone.

STU-II replaced the STU-I, KY-3 and the Navajo I. The last was a secure telephone in a briefcase, "of which 110 were built in the 1980s for use by senior government officials when traveling." The Navaho I also used LPC-10.

Some 10 000 STU-II units were produced.

External links※

• Delusion.org - National Cryptologic Museum pictures
• Pictures of president Reagan using STU-II phone

See also※

• STU-III
• SCIP