90, ch. 32]. Quickly stimulating a new application of his creative talents, she led him to their joint conception of a radio-control scheme in which the transmitted carrier frequency would jump about via a prearranged, randomized, and nonrepeating FH code. A torpedo carrying a properly synchronized receiver could thereby be secretly guided from its launch site all the way to its target. Hedy Lamarr and George Antheil thought such a stealthy "dirigible craft" capability, for missiles as well as torpedoes, would soon be needed by Germany's opponents. Drawing large diagrams while stretched out on Lamarr's carpeted floor, she and Antheil concentrated on them for weeks until they arrived at a secure and feasible FH-SS concept. The system design took special advan- tage of the composer's know-how, in their plan to synchronize the radio transmission and reception frequencies by means of twin, identically crypto- code slotted, paper music rolls like those used in player piano, audio- frequency (!) mechanisms (see Figure 2.8). Indeed, Antheil had already achieved such synchronization precisely in his multi-player-piano opus of the 1920s, Ballet Mécanique [90, p. 185]. Their invention disclosure points out that an FH repertoire of eighty-eight radio frequencies could readily be accom- modated. The Lamarr-Antheil invention promised to be "sturdy and foolproof," and well within the manufacturing capabilities of the 1940s, and its FH secrecy features were enhanced by the inventors' advocacy of short-pulse trans- mission to provide low detectability. But what seems, for that day, to be most Figure 2.8. Redrawn from the Markey-Antheil patent [87]. Upper figure shows mid- course corrections to a torpedo course, made by FH-SR-SS communication from an obseving aircraft. A "piano-roll" recording of the frequency hopping sequence is illus- trated in the lower drawing. The Historical Origins of Spread-Spectrum Communications perceptive in the initial installment [91] of the invention disclosure is pre- sented quite boldly: it is veri