a plurality of relays adapted for controlling power levels by {HEAD ~ means} of controlling {TAIL ~ level combinations} of said contactors, said relays operated by means of logic gates operating upon desired and actual power levels 
of controlling
a plurality of relays adapted for controlling power levels by { HEAD ~ means } of controlling { TAIL ~ level combinations } of said contactors , said relays operated by means of logic gates operating upon desired and actual power levels
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH