In the middle position (e.g., "5"), the tone control is at a "10" relative to how most tone controls read. In other words, it is bypassed. Now, when you turn it to 10, you cut the bass and effectively increase the prominence of the treble in your tone.Conversely, turned to 0, the TBX sounds just like a conventional tone control turned all the way down. The nice thing is that Fender makes these such that the potentiometer finds a little resistance grove at 5, so you know exactly where the middle position is when you turn it to that spot.
How is it connected?
The components are as follows:
- A dual-ganged potentiometer (top = 1 MOhms, bottom = 500 kOhms)
- 82.5 kOhm resistor (orange rectangle)
- 22.5 uF capacitor (orange circle)
The diagram shows how the capacitor and resistor are soldered to the potentiometer(s). The light blue wire is connected as one would any other tone knob (e.g., to the "input" lug of the master volume knob, etc.). You can see the "big picture" in the schematic on this page.
Note: The components come from Fender as a kit rather than soldered together already, so if you feel adventurous, you can experiment with caps and resistors of other values. Honestly, I've never figured out how this works to begin with, so I don't even have any suggestions here. Good luck!
