| 摘要 |
PURPOSE:To detect the presence of an RF signal accurately by discriminating it as the presence of RF signal when a PLL circuit is in the lock state and a detection/smoothing level of a reproducing signal is a prescribed level or over in a digital audio tape player. CONSTITUTION:A level discrimination section 1 detects and smoothes a reproducing signal AS from a recording/reproducing head 5 to discriminate whether or not a smoothed level LRF is a prescribed threshold level LS or over and a PLL lock state discrimination section 3 identifies the lock state of the PLL circuit 2a. A system controller 4 receives a signal from the level discrimination section 1 and the PLL lock state discrimination section 3 and discriminates it as the presence of RF signal when the PLL circuit 2a is in the lock state and the level LRF is a prescribed threshold level LS or over. Thus,the presence of the RF signal is accurately detected.
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