Abstract: A capacitor discharge ignition system employing in-phase trigger, charge and shut-off coils, in a circuit which provides force commutation of the electronic switch and which provides compensation for variations in temperature, inhibition of extraneous triggering of the electronic switch and selective system shut-off. Extraneous triggering may be inhibited by the biasing of the electronic switch as a function of the polarity of the waveforms as well as by the damping of the transient which occurs at the end of the charge of the ignition capacitor. Shut-off is achieved by the shorting of the trigger coil which loads the charge coil to protect the ignition capacitor. Additional protection is provided by the selective shorting of the shut-off coil. Gate protection for the electronic switch is provided by the clamping of the cathode to gate potential.