Identification system for SECAM or SECAM/PAL color television receivers

In a color television receiver subject to reception of composite color television signals inclusive of a chrominance component enclosed in SECAM format;

• said SECAM-encoded chrominance component comprising, during image portions of alternate line intervals, a first subcarrier frequency modulated in accordance with a first color-difference signal, and during image portions of the intervening line intervals, a second subcarrier frequency modulated in accordance with a second color-difference signal, with a lead-in burst of oscillations at the center frequency of said first subcarrier preceding the image portion of each of said alternate line intervals, and with a lead-in burst of oscillations at the center frequency of said second subcarrier preceding the image portion of each of said intervening line intervals;
• apparatus comprising:
• an FM detector, responsive to the received signals, and subject to operation in either a first mode with center frequency tuning corresponding to the center frequency of said first subcarrier, or a second mode with center frequency tuning corresponding to the center frequency of said second subcarrier;
• a triggered flip-flop circuit for providing, when enabled, a pair of half line rate wave outputs of mutually opposite phase;
• a source of line rate pulses timed to substantially coincide with the periods of appearance of said lead-in bursts;
• means, responsive to said line rate pulses and to one of said pair of half line rate wave outputs, for controlling the operating mode of said FM detector such that said FM detector operates in respectively different ones of said modes during the image portions of successive line intervals but operates in only said first mode during each period of lead-in burst appearance;
• first sampling means, coupled to receive an output of said FM detector, and responsive to said line rate pulses and to said one of said pair of half line rate wave outputs, for sampling the output of said FM detector only during alternate ones of said periods of appearance of lead-in bursts;
• second sampling means, coupled to receive said output of said FM detector, and responsive to said line rate pulses and to the other of said pair of half line rate wave outputs, for sampling the output of said FM detector only during the intervening ones of said periods of appearance of said lead-in bursts;
• means for comparing the output levels of said first and second sampling means;
• and
• means, responsive to an output of said comparing means, for disabling said flip-flop circuit only when the output level of a given one of said sampling means significantly exceeds the output level of the other of said sampling means.