| 摘要 |
PURPOSE:To obtain a stable synchronism even when an input television signal is weak by discriminating the reception level of said signal, and providing a smoothing amount control circuit to control the amount of smoothing of a smoothing circuit corresponding to the said level. CONSTITUTION:When the reception level of a television signal is normal, the discrimination signal from a signal level discrimination circuit 17 is at L-level, and a diode 16 turns off, and a second smoothing capacitor 15 comes irrespective of the action of the titled circuit. Therefore, the amount of smoothing is determined solely by a first smoothing capacitor 11. When the reception level comes below a prescribed value, a discrimination signal from the circuit 17 comes to H-level to supply a voltage to the diode 16 via a resistor 18 to turn it on, and the capacitor 15 is grounded. Therefore, the capacitors 11 and 15 come to a parallel connection with each other between a synchronizing signal input terminal 12 and the ground, so that the noise smoothing amount increases, and the vertical synchronism is stabilized.
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