When I was 4 we had a cable box and a TV. I could obviously see that the cable box had its own volume and its video output was its own thing that only went to one channel on the TV itself, because it was what turned the cable wire coming in into a signal, which it put on its output cable wire directed to only one channel, channel 3 or 4, and that that applied to its volume as well. Nobody explained it to me, I could just tell by looking at it. I wasn't a "geek" or a "techno-fetishist." I don't think anyone of any age who thinks about it for more than one second finds this a difficult question, hopefully.