studied by Shannon [30] at BTL, but his comments on these were deleted before republication of his declassified report on secrecy systems in the Bell System Technical Journal. All of these BTL patent filings remained under secrecy order until the 1970s when the orders were rescinded and the patents issued. Alan Turing, who had seen the enormous amount of equipment required by the X-System and heard Shannon explain the sampling theorem, con- sidered the vocoder a non-essential part of its electronics. This led to his con- ception of the Delilah, a secure voice communication system named for the biblical "deceiver of men" [231]. The idea in Turing's design was to perform modular addition of a random key directly to time samples of speech, at a rate high enough to allow eventual speech reconstruction at the receiver, as indicated by the Whittaker-Shannon sampling theorem. The Delilah signal processors were built and laboratory tested by the end of 1944, with random noise from an antennaless radio wired directly to the transmitter and receiver key inputs during the tests. Turing then devised a sophisticated key- stream generator for the system (rather than accept the key distribution problems associated with one-time pads), and tackled the key synchroniza- tion problem. The effort was not completed in time for use during the war. Gustav Guanella, the Swiss inventor who held pre-World War II patents on radars and direction finders employing noise-like signals [13], [14], also Emerging Concepts applied his innovative talents in the related field of speech scrambling sys- tems [61]. A 1946 NDRC report [56] in fact discusses his designs and the level of security which they provide. No direct mention of the ultra-secret X- System was included in this report, which does include descriptions of noise- masking systems and multiplicative signal-modifying systems, as well as methods for protecting the reference signals in TR systems. (An example of good TR-technique is the subject of the next vignette.) It was further noted th