@ET

Here is the frame.

This is the VOB video no. 1 at frame 27792.

I use VirtualDubMod to view these videos.

wattsup, Thanks for the frame grab. I was so focused on trying to see and understand the connections on the
DPDT that I failed to review the volume control. I just reviewed the video again. I was zoomed in too before far as well.
Now I see that he clicks the DPDT twice with his index finger and then the "second frequency" switch with his thumb.
He does not touch the volume control at all.

Do you all agree with this? And what is the assumed use for this volume control?

As long as there are undisclosed items, like in the black box, we will and can never know the real design of what is going on. We can only take from standard physics and engineering practices to surmise it's internal operation. We see the output but not the input or the inbetween.
Some one in the past here said 'It's too bad he doesn't show an oscilloscope'. How profound is that? That led me to abandon reverse engineering these devices. We all got to a certain part and just dropped it across the board.

But if this spurs your curiosity then that is the best part of all because you'll catch the fever like the rest and possibly build something or detect something new!
I hope you do build something or perform a test of some sorts. It should be really cool.

--giantkiller. Good luck on a fresh view.