A source of d.c control voltage is coupled to the input winding via {HEAD ~ a four terminal capacitor} to control {TAIL ~ the impedance} of the secondary winding 
to control
A source of d.c control voltage is coupled to the input winding via { HEAD ~ a four terminal capacitor } to control { TAIL ~ the impedance } of the secondary winding
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH