| 摘要 |
PURPOSE:To display an excellent black-and-white picture without color noise by constituting the circuit that the color killer of a television receiver receiving an SECAM signal is operated when a PAL signal is used as a black-and-white signal in a television signal converting circuit from the PAL system to the SECAM system. CONSTITUTION:A PAL signal detecting circuit 6 detects a color burst by synchronis detection at the color burst inserting period through a low pass filter while utilizing an output signal amplitude of the filter. When the PAL signal has a chrominance signal, an output signal is given from a chrominance signal detecting circuit and a cut-off circuit 7 is in the state passing the color modulated signal being an output of an SECAM modulating circuit 3. On the other hand, when no chrominance signal is included in the PAL signal, i.e., a black- and-white signal, no output signal exists in the chrominance signal detecting circuit 6, the cut-off circuit 7 cuts off the output of the color modulating circuit 3 thereby inhibiting the signal from being given to an adder 5. As a result, since no modulated chrominance signal exists in the SECAM signal and no non-modulation carrier signal exist, the color killer circuit of the television receiver is activated. |
