his time sensing the lower of the above two signals, specifically intended to be the autocorrelation of the upper signal. Fano recalls being startled by his inabil- ity to see at first the extremely narrow peak of the autocorrelation function on the oscilloscope screen. The peak was soon discovered when the lights were turned off. (Photo courtesy of Robert Fano.) signals, another then contemporary matched-filter invention by Ronald Barker [227] definitely used digital signals. Barker's design employs the binary patterns, which now bear his name, as frame sync markers in digital data streams. While this application is not inherently bandwidth expanding, the waveform correlation design objectives in frame sync applications are quite similar to those for SS-MF communication applications, as well as to those for radar pulse-compression. Spread Eagle: Philco Corporation developed this secure inteceptor-control data link for WADC in the late 1950s. Eight hundred chips of a complex binary waveform, transmitted in 200 usec, were used to represent each data bit, providing 29 db of improvement against jamming. The two possible wave- forms, one for MARK and one for SPACE, were detected by a non-coher- ent MF receiver with in-phase and quadrature channels both containing synchronous matched filters. The delay lines in the MF implementation were limited to 100 usec, evi- dently for economy of size and weight. Hence, the 200 usec waveforms actu- ally consisted of repeated 100 usec waveforms, the MF output being sampled twice in the detection process [176]. SECRAL: This ITT missile guidance system development of the late 1950s was a DS-SS design. Branches on the SS Tree Longarm and Quicksilver: These are both early FH anti-multipath systems built by Hughes Aircraft Company, under the leadership of Samuel Lutz and Burton Miller, and sponsored by Edwin McCoppin of WPAFB. 2.3.3 Spread-Spectrum Developments Outside the United States This historical review has concentrated on SS development in the United States for several reasons. 