Abstract: The rest frequency of an oscillator supplying a sub-carrier modulated in frequency by the chrominance signal from a SECAM television transmitter, is servocoupled to a reference frequency during the frame return periods and a phase shift of the oscillator is effected during the line return periods, shorter than the frame return periods. The servocoupling device comprises a reference frequency generator, and a servocoupling loop comprising a switch member and storage means for storing a parameter which controls the rest frequency of the ocillator, and control means for actuating the switch into closed condition, so closing the loop during the frame sweep return periods. The oscillator comprises means for phase setting during line return periods, shorter than the frame return periods.