Video disc players colour detector - distinguishes between proper colour signal and false cross colour signal using line counter system

摘要

The colour detector, for video disc players, distinguishes between a proper colour signal and a cross colour signal (caused by colour interference) and only produces its control signal when a proper colour signal is present. A colour signal whose amplitude depends on colour content is passed to a counter that counts the lines in which a threshold is exceeded (the counter responds only to amplitudes above this threshold). The count restarts after a line in which the threshold is not exceeded. At a given count (e.g. 8) the control signal is released that indicates the presence of a proper colour signal.