The tape motion in the UNISERVO I was controlled by a single
capstan connected to a
synchronous motor. Supply and take-up reel motion was buffered via a complex pulley-string-spring arrangement, as the design was prior to the invention of the
vacuum column buffer. The tape drive contained a permanent leader, and each tape reel had a connector link to the leader. The nickel-plated phosphor bronze tapes were very abrasive, and to counter this problem a thin plastic wear tape was slowly moved over the recording head, between the head and the tape, preventing the recording head from quickly wearing out. The metal tapes also were dirty, and a slowly renewed felt wiper collected tape debris. The UNISERVO I had a high-speed rewind capability, and multiple drives on the UNIVAC I could rewind while others continued with data processing reads or writes. The later UNISERVO IIA and IIIA omitted the plastic wear tape and felt wipers, since they were primarily used with
PET film-base magnetic tape. Both continued the use of single capstan drives and were vacuum column designs. The IIIC and later tapes used
NRZI encoding to be compatible with the
IBM 729 series tape drives which set the industry standard for data interchange. Ironically, IBM then later switched to phase encoding in its 1600-bit-per-inch tape generation because of its superior data reliability. ==See also==