Using the CA3140 integrated circuit, this switch was found in the June 1986 Radio Electronics magazine. Sensitivity adjustment is made at the trimpot in series with the sensor.
This circuit is from old European documentation. R1 depends on the output voltage of the...
This circuit can be used in an experimental link for educational purposes. based on an integrated 4093....
This circuit provides just over ½ W to a small speaker. We found this configuration in an old...