| 摘要 |
PURPOSE:To eliminate the blocking phenomenon during the channel selection without lowering the noise eliminating effect, by providing a circuit which eliminates the noise of the black side output the synchronous signal level of the video signal to be supplied to the AGC circuit and then discontinuing the working of the circuit when the channel is selected. CONSTITUTION:The IF and AGC cirucit A are provided to control via the input level of the antenna 1 the gains of the tuner 2 and the VIF amplifier 3 of the TV picture receiver. Then the noise eliminating circuit formed with the transistors TR16-17 is installed to the circuit A, and the collector of the TR18 is connected to the base of the TR17 of the noise eliminating circuit. And the defeat signal supplied from the channel selection part 6 is applied to the base of TR18. Then the TR18 is turned on forcedly when the channel is selected with the noise eliminating circuit turned off each. Thus the blocking phenomenon can be prevented during the channel selection without lowering the effect of the noise eliminating circuit. |
