JPS6477390A - Chrominance signal line discriminating circuit - Google Patents

Abstract

PURPOSE:To execute a line discrimination without an adjustment but accurately and stably by detecting the ID frequency of a previous line and a present line for every line, using the comparative output of the frequency of the obtained previous line and present line to discriminate the line, in a SECAM system. CONSTITUTION:In a flip flop 12, the rise of a burst flag signal from an input terminal 11 is detected, a Q output and a Q' output whose levels invert every horizontal period are formed and as the outputs of AND circuits 13 and 14, outputs to become higher level in the non-modulating carrier interval of a FM- modulated line sequentializing chrominance signal to be supplied to an input terminal 1 are alternately formed every horizontal period. By this output, switching circuits 3 and 5 are controlled, the level of a line ID signal is sampled and held by capacitor 4 and 6 alternately every horizontal period and the two are compared in a comparing circuit 7. In an Ex-OR circuit 9, an exclusive OR of the comparative output of the comparing circuit 7 and the Q output on the flip flop 12 are formed and removed from an output terminal as a line discriminating signal.