e Doppler spread of the signal, could be improved dramatically. Rechtin's solution was to adjust the receiver's local oscillator automatically to eliminate Doppler variations, thereby sig- nificantly reducing the receiver's noise bandwidth. This automated system used a correlator as its error detector, with the correlator inputs consisting of the received signal and the derivative of the estimate of the received sig- nal. The resultant device, called a phase-locked loop (PLL), with its chrac- teristics optimized for both transient and steady-state performance [166], was a key ingredient of all later JPL guidance and communication systems. Surprisingly, when attempts were made to patent an advanced form of PLL, the prior claim which precluded the award did not come from television, which also had synchronization problems, but came instead from a 1905 patent on feedback control. In retrospect, Eb Rechtin feels that perhaps his greatest contribution in this area consisted of "translating Wiener's 'Yellow Peril' into English," and converting these elegant results into practice. In struggling with blind-range problems occurring in the integration of a tracking-range radar into the Corporal guidance system, Frank Lehan real- ized that his problems were due to the shape of the radar signal's auto- correlation function. The thought that the autocorrelation function of broad-band noise would be ideal led Lehan to formulate the concept of an elementary TR-SS communication system using a pure noise carrier. In May 1952, Lehan briefly documented his partially developed ideas and their potential for LPI and AJ in a memo to Bill Pickering. Lincoln Laboratory's NOMAC work was quickly discovered, since both JPL's and Lincoln's were sponsored by the Army, and the wealth of information contained in Lincoln's detailed reports was made available to JPL researchers. By the spring of 1953, JPL had decided upon a DS-SS configuration for the Corporal guidance link, and Rechtin, noting applications for his track- ing loop theory in SS co