STU-II
The STU-II was a secure call phone developed by the National Security Agency . It offers up to six users the option of encrypted communication via time sharing. The phone was manufactured by ITT Defense Communications, Nutley, New Jersey. One of the OEM partners was Northern Telecom .
According to information from the NSA's National Cryptologic Museum in 2005, the phone has been in use since the 1980s to this day. It uses the linear predictive coding algorithm LPC-10 with 2.4 kBit / s to digitize speech and the Key Distribution Center (KDC) for key management. The NSA also announced that the STU-II B is the standard telephone for secure narrowband calls.
The STU-II replaced the STU-I , KY-3, and Navajo I phones . The latter was a secure phone in a briefcase, 110 units of which were built in the 1980s for use by senior government officials. The Navaho I also used LPC-10.
A total of some 10,000 STU-II were produced.
