We found this circuit in an 80s Intersil documentation. Modern equivalent operating systems can be used. The potentiometer adjusts the detection level.
We found this circuit with very high input resistance in an old documentation. The circuit is still...
This is a circuit suggested by Linear Technology in a 1980s documentation. The integrated circuit is from...
This two-transistor circuit was found in the January 1994 issue of Electronics Now. The circuit can...