The controller 52 uses {TAIL ~ this approximate average} to control {HEAD ~ the magnitude} of power to both electrodes 
The controller 52 uses { TAIL ~ this approximate average } to control { HEAD ~ the magnitude } of power to both electrodes
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH