Patent US 4,338,900

A fuel metering apparatus in an internal combustion engine is proposed, in which the metering signal is correctable in accordance with the mixture composition and/or the exhaust gas composition, this composition is detected by means of a sensor for at least one component of the mixture and/or exhaust gas, and the sensor signal proceeds to a single threshold switch for evaluation. The output level of the threshold switch is monitored in its course and the correction signal as well as an error recognition signal are derived from it.