Until now, {TAIL ~ the transmission power} has been controlled exclusively by varying {HEAD ~ the gain} of the power amplifier 
Until now , { TAIL ~ the transmission power } has been controlled exclusively by varying { HEAD ~ the gain } of the power amplifier
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH