This large, rotary phone was a prototype for a TEMPESTed telephone. TEMPEST is a cover name that is now used throughout the government and industry to refer to frequency emanations leaking from electronic devices as they are used. Even back in World War II, the U.S. Army was warned about a teletype mixer that emitted signals each time the machine stepped. The signals could be intercepted 100 or more feet away revealing the plaintext message.
This early prototype TEMPESTed telephone was mounted on a plaque and presented to Lowell Frazer in 1985, presumably upon his retirement. Frazer was a communications security mathematician whose leadership spurred government and industry interaction in the development of TEMPEST equipment. He also ensured that TEMPEST concerns were part of the cryptographic evaluation process.
To learn a little about TEMPEST history, read “TEMPEST: A Signal Problem”.
