{TAIL ~ The control voltage} for the three wire configuration is the voltage between {HEAD ~ the two neutral points} 
{ TAIL ~ The control voltage } for the three wire configuration is the voltage between { HEAD ~ the two neutral points }
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD