means suitable for registering, from the end of the spark produced by the spark plug, the signals of the ion current produced and detected in {HEAD ~ the secondary circuit} of {TAIL ~ the device} of each cylinder whose piston is at the top dead centre  
of
means suitable for registering , from the end of the spark produced by the spark plug , the signals of the ion current produced and detected in { HEAD ~ the secondary circuit } of { TAIL ~ the device } of each cylinder whose piston is at the top dead centre
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH