We found this circuit in an 80s Intersil documentation. Modern equivalent operating systems can be used. The potentiometer adjusts the detection level.
Found in na 1969 Electronics World, this circuit makes use of transistors of the time. Equivalent...
The circuit shown in the figure below is suggested by ON Semiconductor (www.onsemi.com), based on...
This circuit was found in the Intersil Databook. The integrated circuit used is uncommon today. R2 sets...