terminals 114 and 116 the polarity diode 108 ensures that the trigger signal is developed in one polarity only and that no trigger signal is developed when the inductive pickup sensor 100 is placed on the spark plug wire 26 in an incorrect orientation the output terminals 114 and 116 may then be coupled to the test instrument 12 in the form of a standard connector such as a pair of banana plugs a cross talk source 118 corresponding to the high voltage pulse that is occurring in the remaining spark plug wires of the set of spark plug wires 24 induces a cross talk signal that is capacitively coupled to the detector 104 via the capacitor 120 capacitor 120 is not a physical capacitor but is a circuit model which represents the effective capacitance between the cross talk source 118 and the inductive pickup sensor 100 the value of the capacitor 120 and the corresponding amplitude of the cross talk signal present at the detector 104 varies according to the physical proximity and orientation of the inductive pickup sensor 100 to any of the spark plug wires of the cross talk source 118 because the detector 104 cannot distinguish between the cross talk signal and the spark signal any cross talk signal that is comparable in amplitude to the spark signal may cause false trigger signals to be generated across the output connectors 114 and 116 fig3 is a schematic diagram of an inductive pickup sensor 200 according to the present invention an inductive pickup coil 202 is inductively coupled to the spark plug wire 26 to develop a spark signal the spark signal is coupled via a pair of lead wires 204 to a primary winding of an isolation transformer 206 the primary winding is magnetically.