Then {TAIL ~ the driver} turns {HEAD ~ the power supply} switch on to provide a constant current to the vehicle battery 
Then { TAIL ~ the driver } turns { HEAD ~ the power supply } switch on to provide a constant current to the vehicle battery
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH