| 摘要 |
PURPOSE:To increase the control accuracy and the working efficiency, by connecting an IF signal producing circuit for control of a frequency discriminating circuit to the input side of a VIF circuit of a TV receiver and performing the control while observing a DC voltmeter connected to the output side of the VIF circuit. CONSTITUTION:The TV signal is supplied to a high frequency amplifying circuit 1 and then fed to a video wave detecting circuit 6 via a mixing circuit 2 and a VIF circuit 4. An AGC circuit 7 controls the circuit 4 with the output of the circuit 6. The output of the circuit 4 is fed to the circuit 2 via a frequency discriminating circuit 5 and a local oscillating circuit 3. Then an IF signal producing circuit 8 for control of the circuit 5 is connected to the input side of the circuit 4. Thus the control IF signal (d) is supplied from the circuit 8 with no input of the TV signal. Then the circuit 5 is controlled while observing the output of the circuit 5 by means of a DC voltmeter 9. |
