The switching circuit is coupled to {HEAD ~ the voltage supply} for energizing the primary winding only to achieve a high speed, energizing {TAIL ~ only the secondary winding} to achieve a medium speed, and energizing both the primary winding and the secondary winding in series with each other to achieve a low speed 
for energizing
The switching circuit is coupled to { HEAD ~ the voltage supply } for energizing the primary winding only to achieve a high speed , energizing { TAIL ~ only the secondary winding } to achieve a medium speed , and energizing both the primary winding and the secondary winding in series with each other to achieve a low speed
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL 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 OTH OTH OTH OTH OTH OTH OTH