Abstract: The device comprises a primary winding in which the spark energy is stored to be transferred rhythmically to a secondary winding with respective voltage step-up transformers acting between the secondary winding and the spark plugs. An amperometric resistor is arranged in series with the diode through which the current flows when the energy is transferred to the plugs. For each spark, there is a corresponding voltage peak across the terminals of the resistor, whereby a failure to detect the presence of the peak (which is usually converted into a square-wave signal) identifies the absence of a spark.

Abstract: Upon starting or in the event of a malfunction of the sensor for detecting the stage of the engine, the ignition in the various cylinders is controlled according to a sequence different from that used during normal operation. In the case of engines with odd numbers of cylinders, the sequence is completed in a rotation of the driving shaft through 360.degree. and acts on only one cylinder at a time; in the case of engines with even numbers of cylinders, the sequence is completed in a rotation of the driving shaft through 720.degree. and involves a pair of cylinders at a time.