at if a short-period signal was used as a multiplicative signal in an effort to disguise a speech waveform, then the transmission was quite vulnerable to "cryptanalysis." Several long-period code generators were discussed. The historically useful reports [27], [56], [62], [63] of the NDRC were undoubtedly precursors of the postwar demobilization of that civilian orga- nization. Military officials, recognizing the major contributions of the acad- emic world during the war just ended, and realizing the need for a continued strong research base, initiated a program of support for advanced research in the nation's universities [64, p. 98]. First installed at M.I.T., Harvard, Columbia, and Stanford, this joint Services Electronics Program now spon- sors research at many major U.S. institutions. One can view the advanced Telefunken system as an avatar of a TR sys- tem since specialized signals are transmitted to solve the disk synchroniza- tion problem. Another novel variation of TR voice communication was conceived in the U.S. during the war years by W. W. Hansen. This Sperry/M.I.T. Radiation Laboratory scientist is noted for his invention of the microwave cavity resonator and for his joint effort with the Varian brothers in originating the Klystron. In a 1943 patent application [65], Hansen describes a two-channel system (see Figure 2.4) with the reference channel used solely for the transmission of noise, and the intelligence channel bear- ing the following signal (in complex notation): where n(t) is a filtered version of the noise communicated via the reference channel, v(t) is the voice signal, and assuming n(t) and v(t) are at compara- ble levels, A >> B. The intelligence signal is the result of combining a wide- swing noise-modulated FM waveform with a narrow-swing voice-modulated FM waveform in a device "similar in principle of operation to the mixers used in superheterodyne receivers." At the receiver, the reference channel signal is used to reconstruct the first of the above factors, and that in turn is mixed