Navajo I
The Navajo I is a secure telephone built into a briefcase that was developed by the U.S. National Security Agency. According to information on display in 2002 at the NSA's National [Cryptologic Museum], 110 units were built in the 1980s for use by senior government officials when traveling. It uses the linear [predictive coding] algorithm LPC-10 at 2.4 kilobits/second.
The name is most likely a reference to the Navajo Navajo [code talkers|code talkers] of World War II.