Abstract: Two series of phase displaced leading and trailing electrical signal wave forms of a potential level proportional to engine speed are generated in timed relationship with the engine and an absolute pressure transducer produces an engine manifold absolute pressure electrical signal of a potential level proportional to engine manifold absolute pressure. The engine manifold absolute pressure signal and the leading and trailing electrical wave form series are compared by respective comparator circuits. While the potential level of each of the leading electrical signal wave forms is equal to or greater than that of the engine manifold absolute pressure signal, the corresponding comparator circuit produces an output ignition dwell signal and when the potential level of each of the trailing electrical signal wave forms has increased to that of the engine manifold absolute pressure signal, the corresponding comparator circuit produces an output ignition signal.

Abstract: A first and a second series of phase displaced leading and trailing electrical signal wave forms of a potential level proportional to engine speed are generated in timed relationship with the engine, the potential level of the first series being greater than that of the second series over the engine speed range, and an absolute pressure transducer produces an engine manifold absolute pressure electrical signal of a potential level proportonal to engine manifold absolute pressure. The engine manifold absolute pressure signal and the leading and trailing electrical wave form series are compared by respective comparator circuits.