When {TAIL ~ transistor Q1} is driven to a conducting condition, current flows from {HEAD ~ the voltage source} Vs, via line 11, through the lower winding L1 of the primary of transformer T to ground via the now conducting transistor Q1 
When
When { TAIL ~ transistor Q1 } is driven to a conducting condition , current flows from { HEAD ~ the voltage source } Vs , via line 11 , through the lower winding L1 of the primary of transformer T to ground via the now conducting transistor Q1
REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD 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