"Jim Sewell" says: > A friend of mine that repaired computers said he ran across an > old disk drive that was used in WWII. There were no disk drives in WWII. There were barely computers. Hell, there was barely magnetic audio storage -- on steel wire! I sent the same reply privately. But disks were used in a WWII voice security system -- phonograph disks... I just learned about this system a few weeks ago. As anyone who has read Kahn knows, the early secure voice systems weren't secure; trained listeners could even understand the scrambled system. Some folks at Bell Labs were asked to design one that would work. The eventual system -- known as SIGSALY, or as Project X (and the end units were called X terminals, which is probably the only time that phrase was ever used for something that is secure...) -- utilized a vocoder and a one-time pad. The one-time pad was recorded on two high-quality phonograph records, each of which held 15 minutes of keying information. SIGSALY terminals were quite large -- they took up 30 seven-foot bays. And they needed a *lot* of air conditioning. But the system did work, even over transoceanic radio links. Churchill had one in his underground office in London, in fact. References are ``Secret Telephony as a Historical Example of Spread- Spectrum Communication'', William R. Bennett, IEEE Trans. on Communications, Vol 31, No. 1, Jan '83, and ``A History of Engineering and Science in the Bell System: National Service in War and Peace (1925-1975)''.