Secam color television receivers employing tunable notch filter in luminance channel

A colour television receiver for operating in a system where the colour television signal comprises a luminance signal and a subcarrier which is alternately frequency modulated by first and second colour signals, the alternation occurring at the line frequency, said receiver comprising a luminance channel including a notch filter for attenuating the subcarrier, and a colour channel, including delay means, switching means and frequency demodulating means, for simultaneously delivering the colour signal derived from the color television signal being received and the colour signal derived from the colour television signal received at a time T earlier, where T is the line period, wherein said notch filter is a variable notch filter having a control input for receiving a signal determining the frequency at which said notch filter imparts maximum attenuation, and wherein said receiver comprises a circuit, coupled to said frequency demodulating means, for delivering to said control input a signal which is a function of the instantaneous frequency of said subcarrier.