| 摘要 |
PURPOSE:To reduce malfunction and color noises during the reception of an NTSC signal by preventing forcibly the output of an SECAM demodulating circuit from being outputted when a frame frequency switching signal becomes a signal corresponding to the NTSC signal. CONSTITUTION:The output of the 2nd decision circuit 7 is connected to an SECAM demodulating circuit 6 and the 2nd switching circuit 8 and when the 2nd decision circuit 7 decides that a signal is not an SECAM signal, the killer circuit of the SECAM demodulating circuit 6 turns on and the 2nd switching circuit 8 is switched to a side (a). Further, the frame frequency switching signal 11 as the output of a frame frequency decision circuit 10 is connected to the 2nd decision circuit 7 and when the frame frequency switching signal 11 becomes a signal corresponding to the NTSC signal, the 2nd decision circuit 7 outputs forcibly the same signal as the output generated when it is decided that the output is not an SECAM signal. Therefore, the 2nd decision circuit 7 generates the output indicating that the signal is not the SECAM signal during the reception of the NTSC signal as far as the frame frequency decision circuit 10 does not malfunctions.
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