We found this circuit in the Radio Electronics Handbook magazine special edition of 1992. The circuit uses an optocoupler as an electronic potentiometer.
This simple circuit controls the signal amplitude through a photoresistor optical coupler. The...
In the figure we have the way to obtain the Exclusive-OR function with 1 transistor. The circuit...
This circuit uses as an indicator a common micrometer type VU with 200 uA of full-scale current. The...