Abstract: An analog computer for controlling the ignition system of an internal combustion engine. A continuous signal is synthesized corresponding to the ignition advance angle as a function of the engine speed of rotation and of air intake pressure. This signal is synthesized in accordance with a characteristic for the particular engine concerned. The ignition advance signal is used to control commencement of a power supply pulse to the ignition system, with respect to a reference time signal, as a function of the instantaneous speed of rotation of the engine. Preferably the duration of the power supply pulse is maintained constant regardless of engine rotation speed and ignition advance angle. The circuits described for fulfilling these functions are designed for realization as bipolar integrated circuits.