The increasing number of {HEAD ~ the power levels} is achieved by using electrical elements, such as resistors, {TAIL ~ transformers} and others 
The increasing number of { HEAD ~ the power levels } is achieved by using electrical elements , such as resistors , { TAIL ~ transformers } and others
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH