Method of and apparatus for performing low-voltage correction of

Abstract

After sawtooth wave deflection signals are corrected in a summing circuit for position, magnitude, shape, they are keyed by a blanking circuit, within a blanking interval of the video signal, for briefly inserting a low-voltage reference potential. This is done before the corrected deflection signals are capacitively coupled to high voltage amplifying circuits supplying an electrostatic deflection plate of a camera tube. The high voltage amplifiers are equipped with a clamping circuit timed to clamp the high voltage output to a high voltage reference potential during substantially the same intervals in which the low voltage wave is keyed for insertion of the low voltage reference potential. The vertical deflection signals are keyed at low voltage and clamped at high voltage at the vertical scanning frequency. The horizontal deflection signals may be keyed and clamped either at the horizontal scanning frequency or, for saving of expense and equipment, at the vertical scanning frequency. It is particularly convenient for the clamping to take place at the beginning of the blanking interval of the video signal within which keying and clamping pulses are applied to the switching circuits involved in the keying and clamping.