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