Found in Maxim's documentation from the 90's, this circuit uses an integrated from the time providing a 12 V output from 10 to 12 V inputs.
We found this circuit on Radio Electronics from July 1990. It triggers a relay with a touch of the...
These three circuits have different treble responses. We found them in the February 1970 issue of...
This photoelectric cell light relay was found in Radio Electronics magazine from April 1958. The...