On Wednesday, July 5, 2017 at 10:45:04 AM UTC-4, micky wrote:
Got new used car with new used radio

Regarding balance and fade contols, which pop out for adjustment and
then can be pushed in, so that only a little sticks out:

"Adjust the balance (or fade, for the other button) and push the button
back in. The balance (or fade) will be displayed and continuously
updated while the button is pressed".

What does this mean?

How can it update the fade or balance setting? Is the knob not a direct
adjustment but something that controls an electronic circuit?

Regardless of type, it's always controlled an electronic circuit.
The old style were analog, with the control knob being a potentiometer
that changed the resistance in the analog amp circuit.
The new style which have been around now for decades, the knob
is an input to the digital controller, with cpu smarts, that reads
it and then does the adjustment. Not sure exactly how it works,
but would suspect it's a switch that when rotated sends pulses.




I can see
that could be, but what standards would it use for modifying the balance
and fade? Would it use sensors to tell which seats are occupied? I've
thought about that for years** but if any car did this, I'd have thought
I would have heard about it.

IDK how advanced they are in cars, it clearly would depend on what
car you're talking about. For home system, yes there are sophisticated
adjustment systems that use feedback to try to correct for the room
and environment. You might see that on a MB, IDK. But for a basic
car, it works like the old style, you adjust it to your liking.
That's always been enough for me.



Right now, both adjustments are in the middle, and maybe I'd see
something on the display if I turned one of them, but I'm asking here
first.


Good thing, God forbid, the car might explode if you fiddled with
that fader to see how it works.