Question:  I noticed in the CEL-BP headset menu a feature called sidetone tracking on and sidetone tracking off.  How does this feature work? 

Answer: 
Sidetone tracking is enabled or disabled from the BP menu headset / Sidetone menu  screen.
Tracking on:  Sidetone level will follow the MasterVolume level. As the master volume level is increased the sidetone level is also increased and if the master level is reduced the sidetone is also reduced. Use the scroll buttons under the LCD display to adjust the master volume level.If Master Volume is set to-70 for minimum volume level then when the left-hand scroll button is pressedin the sidetone on an active talk rotary knob will follow the master volume to-70 (no sidetone), pressing the right-hand master volume scroll button willincrease the sidetone along with the master volume level. 
Tracking off:  Sidetone level is fixed at the audiolevel set in the beltpack sidetone menu.  Adjusting the master volumeaudio level to minimum or maximum via the scroll buttons will have no effect onsidetone level as it is independent from the master volume level setting selectby the user. 
The two rotary volume talk/listen knobs have no effect onsidetone tracking on / off.