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