This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made at R6. Supply voltage is matched to that of the relay.
This circuit was obtained in an old documentation, but it can be easily implemented with BC548 and...
We found this audio amplifier stage with 500 ohms of input impedance in an old American...
This IR light sensor circuit was found in the July 1992 issue of Radio Electronics magazine. It is...