| 摘要 |
PROBLEM TO BE SOLVED: To prevent a PLL from losing lock in a constant state such as a tape dropout by monitoring a condition where the PLL may lose its synchronization in a constant state such as a tape dropout or a proper condition for causing the condition and resetting frequency to a default value when the condition is detected. SOLUTION: A data-reading device reads data recording on a tape 10 by a reading head 12, passes the signal to a filter 18 through a rotary transformer 14 and an amplifier 16, and performs initialization, approximation, and equalization to a combined PR-1 target. Then, the amplitudes of +2 and -2 of a received three-level signal is established and stabilized by an AGC circuit 20 for stabilization. A signal from the AGC circuit 20 is supplied to a phase synchronization loop 22 for recovering a clock signal and further is passed to a feed-forward equalizer 24 for providing the adaptive equalization to the combined PR-1 target. |
