a unipolar ignition of the invention provides a current waveform at the ignitor plug which initially rises relatively slowly , followed by a transition to a fast rising current which quickly peaks and thereafter slowly dissipates . such a current waveform provides an initially hotter and longer lasting spark which does not harm the ignitor plug of the system or shorten its life expectancy . neither does the spark create stress on the solid state circuitry which delivers the energy to the ignitor plug . to provide the foregoing spark and current characteristics , an inductor having a saturable core is in series with the ignitor plug , and it provides an initially high inductance which limits the rate of current rise at the plug as energy is transferred from an energy storage device to the plug . as the current through the inductor increases , its core begins to saturate and the effective inductance begins to decrease , allowing the current to rise more quickly . as energy is transferred to the ignitor plug , the increasing saturation , decreasing inductance and increasing current complement one another , causing the rate of current rise to increase quickly to a high value desirable for ignition . related features of the invention provide for easy diagnostics of the spark and for timing an ignition sequence and providing a repetition rate which aids in a successful ignition .