Abstract: During starting of an engine, enrichment correction according to engine starting enrichment is executed. After starting of the engine, enrichment correction is transferred gradually with the lapse of time from starting enrichment to normal warm-up enrichment. The transfer speed from starting enrichment to normal warm-up enrichment is changed depending upon whether a throttle valve is in an idle position or not.

Abstract: An air-fuel ratio feedback control system for the internal combustion engine produces a fuel supply control signal by delaying a rich or lean signal obtained by comparing the oxygen concentration in the exhaust gas with a reference value. The turning on of an idle switch operatively connected with the engine throttle valve, a predetermined time after the turning off of the idle switch and the engine speed included in a predetermined region are detected in order to delay the rich or lean signal to rich or lean side by an optimum delay time as selected according to the engine operating conditions, thus feedback controlling the amount of fuel supply.

Abstract: An air-fuel ratio feedback control system is disclosed in which a sensing output representing the oxygen concentration in the exhaust gas of an internal combustion engine is compared with a predetermined set value. The output of the comparator is integrated and the amount of fuel injection is corrected by being increased or decreased in accordance with the integration output having an increasing or decreasing polarity so as to control the air-fuel ratio at a stoichiometrical value. At the time of engine start, the air-fuel ratio feedback control is stopped, and this condition is held after engine start. Further, the holding function is cancelled by a signal representing the activation of the detection output of the oxygen sensor.

Abstract: A liquid sensor for sensing a level of liquid contained in a tank as well as the presence or absence of water remaining at the bottom of the tank is disclosed. The liquid sensor comprises a housing mounted at the bottom of the tank, a liquid level detecting element mounted on the housing, a pair of electrodes arranged at the bottom of the tank to detect water remaining at the bottom of the tank and an indicator operated in response to signals developed by the liquid level detecting element and the pair of electrodes.

Abstract: The oscillation frequency of the output signal of a ring oscillator is changed in response to a change in the relative position between the coil in the ring oscillator and a float including a conductive member and vertically movable in accordance with changes in the level of a liquid to be measured. The amount of electric power consumed by the ring oscillator itself is changed in accordance with changes in the oscillation frequency of the oscillator output signal. The power consumption of the ring oscillator is detected in accordance with the voltage across a resistor inserted in the power line from the electric power source to the ring oscillator, so that when this voltage attains a predetermined value, an indicator designed to indicate that the liquid level has attained a predetermined level is brought into operation.