Detection circuit for detecting standard television signals and nonstandard television signals

摘要

There is provided a detection circuit for TV receiver which includes a frame comb filter and a field comb filter and which generates a luminance signal or a chrominance signal by effecting addition or subtraction upon video signals of two frames adjoining each other included in the received TV signal. This detection circuit includes a synchronization separation circuit, an APC circuit, a frequency division circuit connected to the APC circuit, and a comparator circuit connected to the frequency division circuit. The frequency of the chrominance subcarrier signal is demultiplied by the frequency division circuit. The phase of the chrominance subcarrier signal thus frequency-divided is compared with the phase of the synchronizing signal separated by the synchronizing separation circuit. It is thus judged whether the received TV signal is a standard TV signal or a nonstandard TV signal.