r developing a hybrid pure noise-TR, FH-SR system with one of the two channels frequency hopped to deny offset frequency knowledge to the jammer. Similarly, CDMA operation was achieved by assigning each Early Spread-Spectrum Systems transmitter-receiver pair a different frequency offset between their data and reference channels. Laboratory experiments on various single-link TR sys- tem configurations with two multiplexed circuits sharing the same reference channel were carried out for a channel bandwidth of 3000 Hz and a data bandwidth of 50 Hz. There were several exchanges of ideas with other research groups during the period following Basore's and Pankowski's theses. For example, at Lincoln Laboratory on October 2, 1952, Sylvania, Lincoln, and Air Force per- sonnel participated in discussions led by Meyer Leifer and Wilbur Davenport on the subject of secure communications [137]. In February 1953, Sylvania, Lincoln and Jet Propulsion Laboratory researchers attended the (Classified) RDB Symposium on the Information Theory Applications to Guided Missile Problems at the California Institute of Technology [111], [138]. Detailed records of these kinds of exchanges appear to be virtually nonexistent. (RDB: the Pentagon's Research and Development Board.) As Group 34 studied the TR approach, it became apparent that the SR approach had advantages that could not be overlooked. The task of solving the key generation and synchronization problems for an SR system was given to another of Davenport's Sc.D. candidates, Paul Green. Green's secret thesis [139] is a clearly written comparison of several NOMAC sys- tem configurations, the aim of which is to determine a feasible SR design. Comparisons are based on the relationship between input and output signal- to-noise (or jamming) ratios for the receiver's signal processor, and the degradations in this relationship as a result of synchronization error and mul- tipath. Green deduced that correlation at baseband would require a phase- locked carrier for good correlator performance