Importance

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Abstract

A voltage of a sawtooth generator is present at a capacitor. This voltage is compared to a reference voltage. In case of a deviation, a controllable current source is connected in parallel to a constant current source charging the capacitor. This allows the position of the picture to be maintained fixed by keeping the center of the picture at a preset level. A counter circuit counts lines of a screen picture and produces a control signal. An electronic switch is connected to the counter circuit and to the capacitor for periodically discharging the capacitor after a vertical deflection period triggered by the control signal of the counter circuit. A first comparator circuit is connected to the counter circuit and activated by a signal from the counter circuit and further connected to the capacitor for comparing the actual voltage applied at the capacitor to a reference voltage. A vertical deflection output stage has an input connected to the capacitor. The constant current source is connected to the capacitor for charging the capacitor with a charging current to provide a control signal for the vertical deflection output stage. The controllable current source is connected in parallel relative to the constant current source for controlling the charging current of the capacitor such that the voltage of the capacitor corresponding to the center of the picture screen is maintained at a constant value.

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First Claim