• High Speed, High Density Digital Recording

      Isabeau, John G.; Data Recording Systems, Inc. (International Foundation for Telemetering, 1971-09)
      The wide signal bandwidth attainable with the 960 inch per second longitudinal tape transport, combined with high density recording at about 20,000 bits per inch provide a multichannel 20 Megabit/second recorder with a 64:1 time expansion capability. The tape transport mechanism consists of two solid, flangeless tape packs placed in direct contact with a large capstan. Stability of the tape movement is achieved by use of a control system which provides instantaneous adjustment of the pack contact forces as a function of direction, velocity, acceleration and pack diameter. This results in full versatility when programming the transport motion. The high density digital signal is phase encoded and processed through the recorder as an analog signal, then is demodulated using a phase lock loop to recover the clock. The sample and hold phase comparator controls a VCO at a fixed nominal frequency, followed by a divider. This configuration permits operation at all bit frequencies in a 128:1 range and allows the clock to coast through a 50 bit dropout without bit slip. Demonstrated bit error rate is 10⁻⁶ maximum.