Abstract: A multiple slope ignition spark timing circuit for an internal combustion engine is disclosed which electronically provides a spark timing signal having a piecewise linear advance angle versus engine speed characteristic. A magnetic pick-up sensor produces an AC signal having a frequency proportional to the rotational engine speed. This AC signal is coupled to a programmable voltage slope generator which generates a variable slope voltage that is used to produce the phase difference (advance angle) between a spark timing signal and the AC input signal. An independent timer apparatus produces various timing pulses which result in changing the advance angle versus engine speed characteristic at various predetermined engine speeds. An engine vacuum sensor adjusts the slope produced by the voltage generator and thereby results in a fixed amount of vacuum advance angle being added to the spark timing advance angle versus speed characteristic.