Abstract: The fuel mixture ratio of an internal combustion engine is adjusted by metering out a fuel quantity in relation to the air flow rate through the induction tube. The air flow rate is measured indirectly by monitoring the engine speed (rpm) with an electrical transducer driving a frequency-voltage converter, thus providing a first voltage, while a throttle plate position transducer generates a second voltage. The two voltages are applied to a logical circuit including parallel diodes which selects the lower of the applied signals and presents the resultant voltage as the primary control signal for fuel metering. Various compensating networks may be added to provide additional smoothing and adaptation to the operating characteristics of a particular engine and state of operation. Various fuel metering devices to be used in conjunction with the control circuit are also described.