| 摘要 |
Sweep oscillator circuit for automatic control of the output frequency with a voltage-controlled oscillator (1) (VCO) which controls the matching of the sweep voltage to the deflection voltage UX of a display unit (19), the VCO being set to the phased-in operating condition in each setting cycle, comprising a phased-in and a free-running operating condition, when the display unit is blanked, and oscillating by means of a crystal-precision reference frequency fRef which is stabilised by a comparator circuit (3) at a frequency mid-point, a sample and hold circuit (15) storing the set VCO control voltage as a reference voltage UXM in the phased-in condition for the X-deflection of the display unit for the frequency coordinates and the deflection voltage UX being set on changeover to the free-running operating condition to a pre-defined value Umin and the VCO (100) being tuned accordingly with the deflection voltage UX from Umin to a value Umax and in the frequency from fmin to a frequency fmax. When Umax is reached, changeover to the phased-in condition occurs via a comparator (12) and an R-S flip-flop (6) so that the reference voltage UXM is reset if necessary and a fixed, pre-defined frequency yardstick is always maintained. <IMAGE>
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