the pedal issue is not because of the knee/floor issue. Half the time it's a foot pedal in a bracket with a lever to push the button. And if it's a different style, when opened the insides are the same. I have a few really old cabinets that the controller does not even have a cover with not a lot of protection to keep fingers from toughing hot wires - and the basic mechanizim is still the same
There is a plunger, and as it goes up it shortens the resistance until there is a direct connection. I've seen some that got stuck in the "direct connection" position and they run wide open as soon as you plug them in.
This shows one in the "off" position with the plunger all the way down. There is quite a bit of spring tension to hold it that way.
And the lever is pressed, the plunger pulls upwards, pulling a bar inside the ceramic housing that makes a shorter and shorter connection between the wires (that would be connected to the screw holes at the top).
Until it is "wide open" and there you see that the metal bar on top of the plunger has caused the other metal peices to form a bridge directly connecting the two wires.
What can happen is those pieces get stuck together, either because the plunger is stuck, or I've seen them actually welded together. If that happens, I'm leary as something caused that to happen - when I saw that, the ceramic was cracked and there were scorch marks on the inside of the case - that one was used to see what they looked like inside.