>>4
A billion knobs seems like a lot. Let's say the average knob or switch is a square-quarter-inch in area taken up on the switchbord. Hence you have a billion of that, or 250 million square inches, or 1.74 million square feet. That makes the switchbord about 40% of the size of the usable floor area of Boeing's Everett Factory building, in Everett WA.