Converters are connected in parallel with each other to a pair of electric power lines. A single ionization detector circuit adapts in response to a control input to alter its bias voltage and its gain to selectively enable effective detection of ionization for each of two different operational modes of an internal combustion engine. In one aspect of the invention, the emitter layer is shaped to bound the reflector layer forming an electrical boundary that focuses the reflected electron beam onto a phosphor layer interposed between the transparent layer. It is also applied on forming a side-wall oxide layer at a side-wall of the trench structure and then subjecting the side-wall oxide layer to annealing whereby eliminates oxidation-induced stress of the trench structure. A biasing member is disposed between the keeper and the body member on the threaded fastener to bias the keeper in a direction away from the body member. The pulsing intervals of the LEDs may be related to the readout intervals of the camera sensor array.