| 摘要 |
The retransmission equipment comprises an automatic control circuit of the video/audio ratio in the television signal. This ARC circuit placed between the intermediate frequency translation mixer and the intermediate frequency amplifier comprises a power distributor between a video channel and an audio channel having respectively a video filter and an audio filter, couplers and an output adder connected to the main outputs of the couplers. The sound channel also has a variable gain amplifier, whose gain is controlled by an error signal, so as to keep the video/audio ratio constant. This error signal results from the comparison of the detected amplitudes of the video and audio components sampled by the couplers in the two channels. This circuit also permits the correction of the cross modulation resulting from non-linearities of amplifiers by the control of the same variable gain amplifier. |
