GB1331077A - Method and apparatus for introducing a monochrome television signal into a pal colour television signal - Google Patents

Abstract

1331077 Colour television PYE Ltd 17 Dec 1970 59969/70 Heading H4F A method of transmitting either a P.A.L. colour television signal including swinging burst reference oscillations or a monochrome television signal comprises a switch 9 which selects either the output from a P.A.L. encoder 7 or the output from an encoder 8 which includes the monochrome signal from a monochrome camera 6 and reference bursts at the colour subcarrier frequency and in the same positions in the line blanking periods as the P.A.L. reference bursts, these bursts for the monochrome signal all being at the same phase. A signal at the subcarrier frequency from an oscillator 3 and burst gate signal G from a waveform generator 4 are fed to both encoders 7 and 8, but the P.A.L. identity waveforms I are fed only to encoder 7 to cause the reference bursts in successive lines to be 90 degrees out of phase with each other. The monochrome camera 6 may be replaced by a colour camera, only the luminance information being used by encoder 8. The colour or monochrome bursts are used to establish synchronism between the output from switch 9 and a camera at a separate location, either the output from switch 9 or the output from the further camera being recorded on magnetic tape, synchronism being maintained with the help of a variable delay line (11, Fig. 2, not shown) controlled by a phase comparator which compares the phases of the reference bursts of the signal from switch 9 and an oscillator which controls the further camera and magnetic tape recorder.