PAL four-frame subcarrier phase detector

A PAL frame phasing system for developing a phasing signal synchronized to a system frame reference signal and a PAL composite video signal including at least color burst and horizontal synchronizing components, comprising:

• a color burst detector for developing a color burst switching signal at a two-line period representative of the polarity of burst phasing with respect to said horizontal component and for developing a four-line rate signal;
• a four-line rate detector coupled to said burst detector and responsive to said color burst switching signal and to said four-line rate signal for developing a four-line rate signal representative of the burst phasing repetition rate;
• first means coupled to said color burst detector and said four-line rate detector and responsive to said color burst switching signal and to said four-line rate signal representative of said burst phasing repetition rate for developing a first signal at a four-line period switching rate to said four-line rate signal representative of said burst phasing repetition rate signal;
• second means responsive to said system frame reference signal for developing a second signal at a four-frame rate;
• and
• phase detecting means coupled to said first and said second means and responsive to said first and second signals for developing a third signal representative of the phasing status of said first signal with respect to said second signal.