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