NOISE CANCELING CIRCUIT

PURPOSE:To prevent the contour of pattern from being fogged by providing a 1st means detecting a section while the amplitude is limited by a limiter for a signal for the limiter and a 2nd means switching the level of the output signal from the adjusting means inputted to an adder by the detection signal. CONSTITUTION:An output signal from the limiter 4 is inputted to a limiter detection circuit 8 to detect the section subjected to limiting (amplitude limit) by the limiter 4 from its input signal. An output signal from the limiter circuit 8 goes to an H level if a differentiation pulse or an excessive noise correspond ing to the edge of a video signal exists and goes to an L level for a conven tional noise component. Then a changeover switch 7 is controlled by using an output signal from the limiter detection circuit 8, and an output from an attenuator 6 is inputted to an adder 9 as it is when the waveform is at the L level and the changeover switch 7 is switched so as to the output from the attenuator 6 is not inputted to the adder 9 at an H level.