| 摘要 |
PURPOSE:To enable to monitor the level of the signal itself to be transmitted without transmitting any monitor signal additionally, by eliminating the DC component out of the transmission signal, transmitting the component with addition of the reference DC voltage and then extracting and monitoring the DC voltage at the reception side. CONSTITUTION:The TV signal applied to the input terminal 1 eliminates the Dc component through the DC cut-off circuit 2 and supplied to the modulator circuit 3 with addition of a certain level of DC voltage from the reference DC voltage generating circuit 4 to be transmitted with addition of the carrier wave. The signal supplied to the reception input terminal 10 through the transmission line 8 is demodulated and transmitted to the output terminal 15 via the DC cut-off circuit 14. The output signal of the demodulator circuit 12 is supplied also to the low band pass filter 16, and the DC component is displayed at the indicator 17 and at the same time transmitted to the output terminal 18 to be used as the control signal of the automatic gain control circuit 20. |
