| 摘要 |
PURPOSE:To attain automatic switching of the PAL/NTSC system by utilizing a burst signal transmitted alternately at +135 deg. and -135 deg. at each horizontal period so as to discriminate the standard system in a television receiver possible for multi-system reception. CONSTITUTION:A chrominance signal applied to a terminal 1 becomes a chrominance signal having a burst signal of a prescribed amplitude and inputted to the 1st, 2nd killer detectors 47, 48 and a chrominance subcarrier generating circuit 56. When the presence of the signal in the 1st killer detector 47 and the 2nd killer detector 48 is detected, the signal is regarded as the PAL system color signal. When the signal exists in the 1st killer detector 47 and no signal exists in the 2nd killer detector 48, it is regarded as the NTSC color signal. When no signal exists in the 1st and 2nd killer detectors 47, 48, it is regarded as a black-and- white signal. The PAL color signal/NTSC color signal/black-and-white signal is discriminated by utilizing the burst signal only. |
