Abstract: The phase of local pulses at a line frequency F, produced in the control unit of a camera is synchronized both with the phase of reference pulses transmitted to the control unit from the camera and with that of incoming pulses received by the control unit from the exterior: in the control unit an oscillator of frequency NF (where N is large) synchronized with the incoming pulses sends, through an AND-gate, pulses to a first N-times divider formed of a counter; the AND-gate is controlled by a comparator circuit comparing the phase of the local pulses and the received reference pulses, the latter being formed of pulses which, in the camera, are in phase with the control pulses coming from the oscillator through a second N-times divider permanently supplied by the oscillator.