| 摘要 |
PURPOSE:To raise luminance, and to prevent a picture from becoming dark by detecting electric field strength and connecting detected output of an electric field strength detecting circuit to a luminance controlling circuit at the time of weak electric field or no signal. CONSTITUTION:Television signals are supplied to a video intermediate frequency amplifier detector circuit 2 through a tuner 1, and at the same time, the output level is controlled by an AGC circuit 3. The output is inputted to a luminance controlling circuit 5 through a video signal processing circuit 4, and drives a cathode ray tube 7 through a video output amplifier circuit 6. A luminance controlling circuit 5 is controlled by voltage changed by resistors 8, 10 and a variable resistor 9, and when luminance controlling voltage V1 is raised, the luminance is raised. A threshold level is supplied to a buffer 11 beforehand, and so constituted that when IF AGC voltage becomes lower than potential, output of the buffer 11 becomes larger.
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