Abstract: The air flow rate and the speed of an internal combustion engine are sensed and translated into pulse trains of variable frequency. During a time interval defined by the rpm related signal, a digital counter receives and counts the air flow rate frequency. Subsequently, the contents of this counter are counted out by a pulse train whose frequency is adjustable depending on other engine conditions such as start-up, warm-up, idling, full-load and the like. The apparatus also includes circuitry for generating a control pulse of minimun length.

Abstract: An internal combustion engine which is provided with an exhaust gas treatment system, such as thermal or catalytic reactors, includes a primary regulating system for admitting fresh air to the exhaust system for the chemical processes taking place in the reactors. This fresh air regulation depends on the engine rpm and on the induction tube pressure. There is also provided a secondary air control system, including a three-way valve and an electronic controller and an oxygen probe, located in the exhaust manifold. The probe supplies the controller with a signal related to the oxygen concentration in the exhaust gas and the controller uses this signal to actuate the three-way valve which admits either induction tube pressure or, alternatively, exhaust system pressure, to a control chamber in the primary regulating system, thereby influencing the quantity of fresh air supplied to the exhaust manifold of the engine.

Abstract: Clock pulses are multiplied by a ratio less than 1 of which the numerator is controlled by a reversible counter. The multiplier output pulses initiate new countdown cycles of a second counter beginning with the clock pulse following the onset of an input frequency pulse and ending with the clock pulse following the onset of the next input frequency pulse. The state of the count at the end of the cycle determines whether the reversible counter will be left unchanged, advanced, or counted back and hence, whether the multiplier output frequency will be left unchanged, increased or reduced. The initial countdown value of the second counter is provided by a long term store which determines the frequency multiplication ratio. The circuit is usable to multiply a variable input frequency in a vehicle brake anti-lock system.