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