| 摘要 |
PURPOSE:To obtain an information which relates to a track number by one band pass filter and one amplitude detector by extracting only a specified frequency component in a difference frequency component of a reproducing pilot signal and a sweep local outgoing signal, and deciding a number of a track being in the course of reproducing at preset. CONSTITUTION:A local outgoing signal is inputted by an equal time variation rate from a sweep oscillator 12 to a mixer 11, a reproducing pilot signal is inputted from an input terminal 17, its difference frequency component is obtained by the mixer 11, and a component of 1/2Fx frequency in the difference frequency components is extracted by a band pass filter 13. A magnitude of an amplitude of a component of 1/2Fx frequency is fetched by an amplitude detector 14, converted to a binary signal against a fixed threshold level from an input terminal 18 by a comparator 15, and a track number being in the course of reproducing is determined by a digital operating circuit 16. Also, a clock signal of a constant period is inputted to an input terminal 19, operations of the sweep oscillator 12 and the digital operating circuit 16 are synchronized, and an information for showing a track number being in the course of reproducing is outputted from an output terminal 20.
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