| 摘要 |
PURPOSE:To stabilize the center frequency of an FM modulator, by controlling a multivibrator type FM modulator by an average value voltage of the output signal of an FM demodulator at the recording time. CONSTITUTION:The output signal of an FM modulator 2 which was modulated by the sound signal from an input terminal 1 is supplied to a recording head 4 through a recording amplifier 3. Simultaneously, the output signal of the modulator 2 is supplied to an FM demodulator 9 through a contact (a) at the recording time. Change of the output DC voltage of this demodulator 9 is regarded as fluctuation of the center frequency of the modulator 2. A sound (b) and signal is removed from the output signal of the demodulator 9 by an LPF11 to extract only DC components, and they are fed back to the modulator 2, thereby stabilizing the center, frequency of the modulator 2. |
