| 摘要 |
In a frequency modulator (1) having an adjusting circuit by which frequency modulator an applied luminance signal of a color video signal that contains synchronization pulses is frequency modulated, while the chrominance signal of the color video signal is modulated on a carrier, that has a quiescent frequency if no color information is available. A capacitor is provided for an automatic mode of operation, and is charged or discharged, respectively, in dependence on the period duration of the modulator output signal and in dependence on the period duration of the quiescent frequency of the chrominance carrier. The steepness of the voltage/frequency characteristic curve of the modulator is set dependent upon the charge condition of the capacitor, while the charging-to-discharging ratio is selected such that the charge of the capacitor is maintained constant on average, if the modulator frequency is equal to a predefined nominal frequency and increases or decreases, respectively, if the modulator frequency falls short of or exceeds the nominal frequency during the synchronization pulses.
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