GB1412560A - Pal system colour television signal recording and reproducing system - Google Patents

Abstract

1412560 Colour television MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 5 July 1973 [7 July 1972 (2)] 32050/73 Heading H4F A PAL colour television signal to be recorded is separated into its chrominance and luminance components, an index signal, Fig. 11(g) being derived from the colour bursts and added, during alternate line blanking periods, to either the chrominance signal, Fig. 11(h), or the luminance signal, the index signal being separated during play back and used to operate a switching circuit 129, Fig. 10, to change, during alternate line periods, by 90 degrees the phase of the output of either a burst gate 126 or a variable frequency oscillator 131 fed to a phase comparator 130, the output of oscillator 131 being used to remove jitter in the reproduced chrominance signal. In the embodiment of Fig. 10, the luminance signal is frequency modulated 104 and passed to a mixer 106 which also receives the chrominance signal, Fig. 11 (h), which has been converted to a low frequency and has had the index signal, Fig. 11(g), added to it. The index signal is derived by adding the output of burst gate 107 after it has passed through a 90 degree phase retarder 108, Fig. 11(b), with the same output delayed by a one line delay line 109, Fig. 11(c), to derive the signal of Fig. 11(d), which is passed through circuits 110, 111, 112 to derive the index signal, Fig. 11(g). The index signal is separated from the reproduced signal by separator 127 and controls a multivibrator 128 and hence switch 129, the index signal being removed from the chrominance signal in a gate 135. The index signal may alternatively be added to the luminance signal prior to frequency modulation thereof (Fig. 12, not shown), the index signal being derived from the half-line frequency output of a phase comparator (215) receiving the outputs from an oscillator and burst gate. Either the index signal or the luminance or chrominance signal is then delayed by one line period before the signals are combined.