| 摘要 |
1516315 Television contrast control COMMUNICATIONS PATENTS Ltd 9 June 1975 [11 July 1974] 30862/74 Heading H4R In a contrast control circuit for a television receiver a field effect transistor 15 has its source drain path connected in an attenuator circuit in the signal path while the gate potential is set by the potentiometer 21, to control the attenuation given to the signal. In addition a signal dependent on the beam current of the receiver picture tube is derived from the line time base and applied, via a diode 24, to modify the control voltage applied to the f.e.t. gate and maintain a limit on the beam current irrespective of the setting of the contrast control. |
