A trigger coil generates a trigger signal for application to {HEAD ~ the trigger} of {TAIL ~ the switches} 
of
A trigger coil generates a trigger signal for application to { HEAD ~ the trigger } of { TAIL ~ the switches }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL