 also joined Nicholson as System Engineer in early 1953. Nicholson and Raney almost certainly deserve the credit for coining the now universally recognized descriptor "spread spectrum," which Sylvania termed their Hush-Up system as early as 1954, (see [3], footnote 2). During the second contractual period, which lasted into 1957, Green and Nicholson settled on the form of noise-like carrier which Hush-Up would employ in place of WHYN's FM, namely, a pseudorandomly generated Early Spread-Spectrum Systems binary sequence PSK-modulated (0 to 180 degrees) onto an RF sinusoid. Such binary sequences with two-level periodic correlation were called "per- fect words" by Nicholson. In the end, a variety of perfect word known as an m-sequence was advocated for implementation (more on m-sequences later). Synchronization of the DS-SS signal was accomplished by a sinu- soidally dithered tau tracker (7 = delay). Nicholson and Green's tau tracker invention has been, until recently, under patent secrecy order [119] (see Figure 2.13). As development progressed, the system evolving from the Hush-Up effort was officially designated the ARC-50. Sylvania engineer Everard Book fab- ricated the ARC-50/XA-2 "flying breadboards." In 1956, flight testing began at Wright-Patterson Air Force Base (WPAFB) with WADC Project Engineers Lloyd Higginbotham and Charles Arnold at the ground end of the ARC-50/XA-2 test link and Capt. Harold K. Christian in the air. The assigned carrier frequency for the tests was the WPAFB tower frequency; the ground terminal of the ARC-50 was about 100 yards from the tower antenna, and communication with the airborne terminal was acceptable at ranges of up to 100 miles. Vincent Oxley recalls that tower personnel, and the aircraft with which they were conducting normal business, were never aware of ARC-50 transmissions. While the tests were successful, it must have been disheartening to Buffalo engineers when Sylvania failed to win the development/production contract for the ARC-50. 2.2.4 BLADES2 In the mid-1950s, Ma