The UNISERVO I wasn't phase encoded. The first phase-encoded drive from UNIVAC was the UNISERVO IIIC, which was 1000 BPI, 1 mil Mylar tape, 3600 feet per reel. If it had been phase-encoded, it wouldn't have needed a clock track.
The UNISERVO motors were powered by McIntosh audio power amplifiers. --John Nagle (talk) 19:21, 12 December 2007 (UTC)